eee95ef0ce7c125894357dfcb32ed33bcea1a27f
162
Commits
| Author | SHA1 | Message | Date | |
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  AnachronautandClaude Opus 5
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5732a31b2e |
Stop the allocator starting the directory again for every file in its way
Placing one file on a disk with the source tree on it cost 9.4 million cycles. It costs 1.4 million now, and assembling colours.asm went from 13.9 to 6.0 seconds. sbfsAllocate gave up the moment it found anything in the candidate's way: it moved the candidate past that one entry and STARTED THE DIRECTORY AGAIN FROM THE FIRST BLOCK. With files laid down one after another that is a restart per file, and every restart reads directory blocks off the disk until it reaches the next thing in the way - which is further in each time. Placing one file among 183 of them cost thousands of block reads. The candidate moves along DURING the pass now, and the pass carries on from where it is, so entries later in the directory are tested against where the candidate has got to. On a disk that has been appended to - which is what a disk mostly is - one pass walks it past everything and a second confirms nothing is left. Two passes rather than one per file. IT IS STILL FIRST FIT, and Tests/agree.sh is what says so: the machine and SplitDisk build the same tree and the images still match byte for byte, which they could not if allocation had started choosing differently. The argument is that the candidate only ever moves past something that genuinely overlaps it, and when it does there is nowhere below to go - the entry in the way covers everything up to its end and begins before the candidate ends. The first attempt at this was slower than what it replaced, by three times. It finished the pass and jumped to the FURTHEST overlap, which sounds better and is worse: with files laid contiguously only one entry ever overlaps, so the old early exit was the fast path and reading the whole directory to find the one thing was pure loss. The number of passes was never the thing to fix - restarting them was. The boot slot in the test fixtures goes from 32 blocks to 40, which is what a shipped disk has. Stage two is 8,231 bytes and 32 blocks is 8,192: a fixture tighter than the thing it stands in for fails on a change the real disk would have taken, and says "the boot slot is too small" rather than what actually grew. WHAT THIS DOES NOT FIX is assembling CosmOS, and that is worth saying plainly. It takes 654 million cycles on the mirrored disk and 653 million on a flat test disk with a sixth as many files, so it is not a filesystem problem at all. Cycles per byte of source climb with the size of it - 1,383 for colours.asm, about 3,000 for Edit.asm, 6,290 for cosmos.asm - which says the native assembler is superlinear in what it reads. That is a separate thing to go and look at. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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7073b972e6 |
Say what went wrong, and give the file tools room for a path
The makefile on the disk was fine. "Makefile" is not "makefile", and SBFS names are case sensitive - but neither tool said so, and both failed in ways that pointed somewhere else. MORE PRINTED A NUMBER THAT MEANT NOTHING. "cannot find the file, error 2" invents a vocabulary the system does not have: the filesystem library documents its answer as zero or not zero, never as a code, so 2 could not be looked up anywhere. It says "there is no file by that name" now, which is the only way opening fails that a person can do anything about, and is nearly always a name typed slightly wrong. EDIT SAID "0 LINES", which is also what an empty file that IS on the disk says. A name typed slightly wrong therefore looked exactly like the document you meant to open, right up until you saved it somewhere new. It says "new file" instead. Two bugs came out of writing that, and both are worth more than the feature. The first is mine and the label lied to me: loadNothing is not where a load FAILS, it is where every load FINISHES, reached at the end of splitLast on files that opened perfectly well. A flag set there on the strength of the name was set on everything. It is called loadDone now, and the failure has its own name. The second is older and general: a program is loaded once and may be run many times, so "load Edit.sbx" then "run" twice is two sessions over one copy of the Data Segment. Anything a session changes has to be put back by the session. A zero written in the Data Segment is the state a program starts in the first time and never again - and cosmosEdit runs Edit twice from one load, which is why it caught it immediately. AND THE FILE TOOLS COULD NOT ADDRESS THE TREE THEY NOW HAVE. Edit took 23 characters of name and More and Type took 29, which were right when everything lived in the root. With the sources mirrored onto the disk, "/Source/CosmOS/Assembler/classify.asm" is an ordinary thing to type - thirty-seven characters, cut down to a name meaning something else, or nothing. All of them take sixty-three now, which is what the shell reads of a command line, so nothing longer can arrive. Wander with it, since a directory is a path too. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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0852666e73 |
Mirror the source tree onto the system disk
A list of files in a makefile goes stale the moment somebody adds a program and forgets to name it, and what they forgot is invisible until they go looking for it on the machine. So SplitDisk gained a mirror command and the disk rule is one line: putting a file where the others live is now the whole of putting it on the disk. EVERY FILE GOES THROUGH put AND EVERY DIRECTORY THROUGH mkdir. That is the point of it - mirror adds a walk and no filesystem code at all, so anything the format refuses here it refuses everywhere, in the same words. What is new is the walk, and the walk is what the six checks in Tests/disk.sh are about: that it goes all the way down, that it leaves dotfiles and named directories behind, and that a name too long stops it. REFUSED RATHER THAN SKIPPED, because a disk quietly missing a file is the exact failure a mirror exists to prevent. Which meant four sources had to be renamed - a directory entry holds 22 characters and they were 23, 23, 24 and 29: 16bitSegmentedSieve.asm -> 16bitSieve.asm 16bitSegmentedSieveModern.asm -> 16bitSieveModern.asm consoleInterruptTest.asm -> consoleInterrupt.asm controllerWriteTest.asm -> controllerWrite.asm The test names in the manifest are unchanged, since those are identifiers and every recorded result is filed under them. Only where the source lives has moved. The entries are sorted before anything is written. readdir hands them back in whatever order the host filesystem feels like, and a disk image that comes out different from one run to the next is an image no test could compare against another. The disk grew from one megabyte to four and from 192 directory entries to 1,024. The sources are 2,850 blocks and the mirror filled the old directory on its first run, which is a thing that should not need thinking about again. The Tests fixture disk is deliberately NOT mirrored. It is a controlled fixture with known contents, and the shipped disk is the one meant to be useful; they want different things. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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ff4b025058 |
Make the cursor blink while the machine is waiting, and show how the palette works
THE CURSOR DID NOT BLINK, and the reason is worth stating: it blinks on the machine's clock, and the machine's clock had stopped. A console waiting on a key stops the CPU, so no cycles passed, so the phase never moved - and the one moment somebody is looking at a cursor is the moment they are being asked to type. Waiting is now charged as IDLE CYCLES, which is what they were built for: a machine stopped on a device is not using memory, the same distinction WAIT makes, arrived at from the other direction. And the devices are told as it happens rather than when the instruction finally finishes, because a display controller does not stop blinking because the processor is waiting on a keyboard, any more than a disk stops turning. A keyboard file can now say NOTHING happened. A zero is a byte no keyboard sends, so it is free to mean "a moment went by with nobody typing" - which is the commonest thing behind a window and the only thing a file otherwise could not express. That unlocked the whole waiting path: three checks that the cursor is lit, then dark half a second later, then lit again, which is what blinking is. And Programs/Examples/colours.asm, because the palette had nowhere a newcomer could read it. It prints the sixteen pairs, prints each one again turned inside out, and then CHANGES ONE by writing three bytes into the palette - so the difference between using the colours a machine wakes up with and choosing your own is visible in one program. Its header explains what a cell is, what the attribute nibble does, why palette entries are four bytes rather than three, and why video memory has to be reached through the controller. The manual now says where the palette lives and points at it. SplitLint found a redundant RSTA in the example, which was worth acting on rather than suppressing: the zero was already in A from the mode write two lines up, and saying so in a comment teaches that SETD does not touch A, which is a thing worth knowing. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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d6feddd1b6 |
Give the console colour and a cursor
COLOUR COSTS A NIBBLE AND NO HARDWARE. A glyph is drawn in palette indices 0 and 1, paper and ink, and a cell's attribute nibble adds sixteen to both - so sixteen banks is already sixteen ink and paper pairs, and all that was missing was a register saying which one the console draws in. That is port 0x06, read as well as written like the rest. The palette a machine wakes up with is arranged so that HIGHLIGHTING IS ONE BIT: banks 0 to 7 are colours on black, banks 8 to 15 are the same colours as paper with black ink. So attribute XOR 8 turns any pair inside out. That is a convention rather than a rule of the machine - the device only ever adds the nibble and looks the answer up - but it is the convention that makes a highlighted line and a cursor free. Bank 0 is still grey on black, so nothing that was written before this has changed colour. THE CURSOR IS THE SAME BIT AGAIN. It is drawn by turning its cell inside out rather than by putting a block over it, so the character underneath stays readable, which matters to somebody editing a line. The device draws it rather than the window, because on a machine with a screen a cursor is a hardware feature - one drawn by the presenter would not be in a picture the machine saved. It blinks on the machine's own clock, half a second each way, so the phase is a pure function of the cycle count and a screen saved at a given cycle is the same screen every time. A blink on the host's clock would have made every saved picture a matter of luck. Off unless asked for, with bit 2 of the control port. That is right for a machine - a program painting its own screen does not want something blinking in the middle of it - and CosmOS asks for one at boot. It also asks again when it takes the console back from a program that has stopped, because a program handing key mode back the way it was told to writes zero, which turns the cursor off. The shell owns the prompt, so the shell is what makes sure there is something blinking at it. Nine more checks in Tests/video.sh, to 41: that the attribute colours the ink and not the paper, that XOR 8 turns both, that it reads back, that a cursor appears where the registers put it and only when asked for, and that it goes dark again half a million cycles later. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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978aec4809 |
Let the console edit a line, and let a file be a keyboard
BACKSPACE REACHED THE SHELL. A terminal in line mode does not hand a program every keystroke: it collects a line, rubs out a backspace, and delivers the finished thing at Return. CosmOS has always relied on that, and behind a window there is no terminal to do it, so the raw 0x08 went into the command buffer. Correcting a typo produced a line that looked perfectly right on the screen and matched no command at all - "I do not know: help". So the console does it, because behind a window the console IS the terminal. In key mode it does not, and must not: a program in key mode asked for every keystroke as it happens. CosmOS now asks for eighty columns at boot. Its own help text is seventy-four characters wide, and dir, the monitor and the assembler's messages all assume room. The machine still wakes up in the smaller mode, which is right for a machine - it is the system that knows what shape of screen its own output needs, and a game that wants forty columns says so. AND A FILE CAN BE A KEYBOARD, which is the part that matters beyond today. The console behind a window is not the console behind a terminal, and until now the difference was unreachable: it broke twice in two days and a person typing found it both times. --keyboard installs the same hook a window does, so the same path runs, and the manifest has a column for it. cosmosTyped types "halp", backs over it, arrives at "help", and requires the help to come out. Verified by removing the rub-out, which loses the whole help text. It does not test the window. Voyager's key queue and everything about presenting frames are still out of reach. It tests the console, which is where the logic is. Along the way: VOY_OBJS was missing from the dependency include, so voyager.o never rebuilt when a header changed. EmulatorOptions grew a field, Voyager kept an object that disagreed about the size of the struct, and smashed its stack on every run. A clean build hides it and 'make sanitize' cleans first, so that would never have found it either. Tests/voyager.sh did, by failing all 115 tests that start the machine - which is the differential test earning its keep on a bug that has nothing to do with what it was built to check. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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761c11a66b |
Add run-voyager, and make running depend on the disk
The jitter was a stale disk. An image built before the escape sequences came out still had the old Snake on it, which sends ESC [ H every frame: the console swallows the escape, because it is below the font's first character, and then draws "[H" as two ordinary letters. So every frame began two characters to the right and one line further down than the last, and the board walked down the screen. Not timing at all. WHAT IS ON A DISK IS WHATEVER WAS BUILT WHEN THE DISK WAS MADE, and a machine whose console has changed will start that image quite happily. That is the compatibility break we chose when the parser came out, and it is fine - but it should not be a puzzle, so both run targets depend on the disk rather than merely using it, and both READMEs say why. run-voyager boots the same disk on the machine with a screen. It existed only as EMU=../Voyager in front of run-cosmos, which is not a thing anybody should have to know. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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310804e267 |
Give Snake back the speed its comment promised, and present in step with the display
Two things, one certain and one likely. THE CERTAIN ONE IS NOT THE WINDOW'S FAULT. Snake's pause loop said "at the emulated rate this is about an eighth of a second", and it was, when a cycle was one instruction. A cycle became one memory access, every loop in the machine got dearer, and this one silently doubled: the game has been running at half the speed it documents ever since, in a terminal as much as in a window. Measured rather than guessed - the inner loop is a DECA and a BNA, one byte and three, so four cycles a turn, and a whole run went from 3,848,610 cycles to 1,920,504 when the outer count came down from 256 to 122. Almost exactly half, which is what the arithmetic said it would be. That is the cost model change reaching a program nobody thought to re-measure. Worth looking for others: any loop tuned by eye before that change is running at half its intended speed. THE LIKELY ONE is the frame limiter. Without the vsync hint, Raylib sleeps towards sixty frames a second on its own clock, which beats against a display refreshing on its own - frames shown twice or skipped, and the machine handed an uneven number of cycles each time, since it takes its budget from the wall clock. The hint puts presentation in step with the screen. SetTargetFPS stays for a driver that ignores it. Snake is one byte bigger, because RSTB became INIB. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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43a05b3df1 |
Replace the escape parser with cursor registers
The console had grown an ANSI parser, and that was the wrong shape. ANSI exists because a screen used to be on the other end of a serial line and a byte stream was the only channel there was. This screen is memory the program can already address, so reaching it by sending characters for a state machine to take apart is a middleman for something the machine does better - and it meant accepting an open protocol somebody else defines, in hardware, with no natural end to it. Everything else on this machine is registers. So the console gets three: cursor row at 0x03, cursor column at 0x04, and a command port at 0x05 where 1 clears the screen. Both cursor registers are READ as well as written, which is the thing an escape cannot do without sending a query and parsing a reply - a routine that wants to put the cursor back where it found it can now ask. Clearing is one command against a thousand cells walked one at a time. Snake and Life are smaller for it: 2,168 bytes to 2,163 and 1,410 to 1,396. A HOST TERMINAL STILL SPEAKS ANSI, and bridging to the host is the emulator's job, the same job it does reading standard input. So the escapes are now GENERATED, outbound, for the set this device chooses, rather than parsed inbound as though the machine were a terminal. The set cannot grow behind our backs because we are the ones saying it. The cursor is announced lazily, at the next character rather than at the register write, so setting a row and a column costs one sequence rather than two. The console's block widens from three ports to six, which registryTest noticed: it had been asking about port 0x05 precisely BECAUSE nothing was there, and the console had just moved in. Re-blessing it would have left it checking nothing, so it asks about 0x80 instead - clear of the console, the disk, the screen, the controller, and the sound device coming to 0x40. Six checks in Tests/video.sh swapped from the sequences to the registers, including that the cursor reads back and that one sent past the edge is clamped rather than refusing. Those checks also stopped counting bytes from the ends of a file, which had quietly started measuring an escape the moment the console began announcing the cursor. SplitLint caught the one thing worth catching in the port: the clear command leaves A at 1 and key mode is also 1, so the second load looks redundant. Acting on it would tie a console command to a console mode by coincidence, and break silently if either ever moved, so it is suppressed with that reason rather than removed. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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Anachronaut
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79727044b7 |
Reboot, and the machine device that makes it possible
Until now the only way to restart was to stop the emulator and run it again, which meant the one thing the machine could not do was the thing Once was written for. The loop now closes without leaving it: > Once /System/Boot/bare.bin next start: /System/Boot/bare.bin, once > Reboot starting again stage two just this once: /System/Boot/bare.bin bare metal: no system, just this Writing 1 to port 0x13 asks the machine to start over. A PORT RATHER THAN A SERVICE, because a reset has to work when the system does not: something only askable through SWI would be unavailable in exactly the case that wants it most, and a program that owns the whole machine has no system to ask. It is device class 0x04, in the range kept for the machine rather than among the peripherals, because it is not one - it is not attached to anything and cannot be unplugged. WHAT A RESET REPEATS IS HOW THE MACHINE STARTED. Named an image, the emulator places it again; named none, the ROM is shadowed again and reads the disk. Anything else would mean a reset changed what the machine IS, which is the one thing a reset must not do. Both are tested. Taken between instructions, because a device cannot restart the machine from inside the instruction that asked: the CPU is part way through a step and its state is not yet anything a reset could leave behind consistently. The disk stays attached and keeps everything written to it - that is what warm means. The vector table is cleared, which is the one deliberate departure from leaving memory alone: a vector points into whatever installed it, and after a reset that program is not running, so a handler left behind would aim an interrupt at an address belonging to something gone. It is the argument CosmOS already makes at exit, applied to the machine. Reboot is 45 bytes, most of them the word it prints. |
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Anachronaut
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7b28f48f52 |
Once: start something else on the next start, and only that one
A program that owns the whole machine had nowhere to run. It cannot be started from the shell, because starting it means there is no shell, and pointing boot.cfg at it means a machine that keeps starting it - which is a poor place to find a mistake in something written five minutes ago. Once writes /System/Boot/once.cfg, in the same format as boot.cfg and read with the same routines, because a second format for one setting would be a second format. The loader reads it before boot.cfg and DELETES IT BEFORE IT JUMPS, which is the only moment there is: after the jump the loader does not exist. Consumed by being read rather than by working, so a one shot that hangs cannot hang twice - the request is gone before the image ran, and the next start reads boot.cfg like any other. THE BOOT STATE IS NOT TOUCHED, and the first version got that wrong. It marked the start the way any other start is marked, and then every successful bare metal boot reported that it had never arrived - because a program with the whole machine has no filesystem to clear a mark with and is doing nothing wrong by not having one. Found by running it: the image printed its line and the next start still said the last one did not. Three disks, each a start further along, so none of the tests depends on another having run. The loop is closed on the machine now: write it in Edit, assemble it with Asm, ask for it with Once, restart, watch it own the machine, and the system comes back without being asked. |
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Anachronaut
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89c667848b |
Edit read a file into a buffer it never checked the size of
Opening hello.asm showed a thirty one line file as three, one of them cut short. Opening it again hung the machine: the emulator kept running and nothing ever answered. Entry is the buffer a line is read into, and it is followed in memory by TextHead and ArenaFree - the head of the document, and the pointer its line allocator hands out. The loop that splits a file into lines copied characters in WITH NO BOUND AT ALL, so a 94 character line wrote thirteen bytes over both of them. The list head then pointed into the middle of the text and the allocator handed out an address inside the file, which is why the second open walked a list that led back into itself for ever. Typing was always safe. osReadLine is told how much room there is, so a new document behaved perfectly and a source file did not - which is exactly how the user found it, and why it looked like a mystery rather than a bug. The bound is there now, and the buffer is 128 characters: what a line is everywhere else on this machine, the same number configuration files use, rather than a second answer to a question already answered. hello.asm fits. A file with a longer line is REFUSED rather than shortened. This is an editor - a line cut on the way in would be written back cut, and the file damaged by having been looked at. It says so and exits with a status of one, which it can do since this afternoon; the file is byte identical afterwards, and the test checks that. Opened twice in the test, because once is not enough to see it: the first open does the damage and the second is what never returns. This is the third time this shape has turned up: a buffer written past its end into the variables that happened to follow it. The prompt walked off CwdText into the shell's own command names; the assembler's output ran into its label table. Every one was found by a person using the machine. |
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Anachronaut
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87d819847e |
A program can say how it went
SWI osExit takes a status in A, and the shell keeps it. Fifty eight exits across twenty three programs now say deliberately whether they worked: 25 did what they were asked, 24 did not, 9 were asked wrongly. Compare is the exception and says so - one there means the files differ, which is a result rather than a failure, the way diff has always had it. IN A RATHER THAN Q, which is not a departure from the rule that a service answers in Q. This one takes an ARGUMENT, the way osPrintNumber takes A and B, and it never returns to answer anything. A is free precisely because a return would have put it back - and Q is the ALU's output, so a small number costs four instructions there against one in A. The shell does not print it. A program that failed has already said so in words and a number beside that is noise, so osLastStatus hands it back and Status is the program that shows it. That indirection is the point: the number exists for the thing that cannot read words. MARKING THE EXITS FOUND A DEFECT ON THE FIRST RUN. Type and More printed why they had failed and then fell through into the success exit, reporting that all was well. Nobody had noticed, because while the only reader was a person, the person could see both the complaint and the claim. Two smaller things. Snake sets the console to line mode and then exits with zero, and the linter flagged the second RSTA as redundant - an exit status and a console mode, equal by accident, which is the class that must never be collapsed. And the README still taught answering by writing into the frame, three months of habit that SRET replaced yesterday; that section is gone and the one describing SRET stands in its place. |
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Anachronaut
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b4206673a6 |
The clean install disk is one the machine can start itself from
make run-cosmos handed the emulator a boot image AND a disk, so it took the direct path every time: memory placed from outside, nothing on the disk consulted about it. The whole boot chain was built and tested and then not used by the one command that runs the system. The disk is formatted with a boot area now, stage two goes into slot zero as raw bytes, and the system is an ordinary file at /System/Boot/cosmos.bin - which is what boot.cfg would choose between if there were one. There is not: stage two falls back to that name when the file is missing, and a clean install with nothing to configure is the right default. run-cosmos names no image, so the machine starts itself. The old behaviour is run-cosmos-direct, which is worth keeping and worth naming honestly: it is what a debugger does, and it is what to use when the thing being debugged is the boot chain, since it skips the boot chain. /Source gains stage1.asm and stage2.asm, so the machine can rebuild what starts it. Everything stage two includes is already in /Lib, so Asm stage2.asm on the machine produces the bytes a boot slot takes. Stage one is the exception and always will be: it is the ROM, and the one part of this that a disk cannot replace. Second slot left empty, which is what makes replacing the first survivable. |
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Anachronaut
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f1cc2e56b2 |
The last handler that knew a frame offset
handleReadLine used DP1 for the frame and the conversion only looked for DP2, so it kept the whole dance - and the dance had become a no-op that looked like work: MVQA copied Q into A, A was written over the saved Q, and RETI restored it, which is where it started. readLine leaves the length in Q and SRET keeps Q, so the answer simply stands. No handler in CosmOS knows what an interrupt frame looks like now. The 0d02 and 0d05 offsets still in the file are structures - an SBEX header, an entry in the instruction table - and not frames. |
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Anachronaut
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c8c9f0b363 |
SRET: a handler answers the way a subroutine does
CALL saves A, B and Data Pointers 0 to 2 and nothing else, which is exactly why Q and DP3 are how a subroutine hands something back. An interrupt saves all of it, so a service with an answer had to reach into its own frame and un-save two fields by hand: MVSD.2 DPUP.2 0d02 ; the saved Q, by an offset it had to know STA.2 RETI Thirty places in CosmOS did that. Every one knew the frame's layout by heart, and all thirty would have gone quietly wrong the day the frame gained a field - the same duplicated fact this project keeps being bitten by, except duplicated into thirty places AND into the CPU. SRET is 0x76, in the seat the block split left for it. It is RETI's frame with RET's rule applied: A, B and DP0 to DP2 come back, the saved Q and DP3 are dropped, and the Interrupt Flag is restored from the frame - only that bit, so carry survives a service the way it survives a call, and there is one rule rather than two. RETI stays exactly as it was: a hardware handler has nothing to say and must leave no trace. CosmOS is 10,969 bytes against 11,122, and no handler knows a frame offset. TWO MISTAKES WORTH RECORDING, both mine, both caught by tests. The first conversion matched STA.2 with a regular expression that did not allow a trailing comment, so it ran past the end of one handler and into the next. The second understood the pattern and still got it wrong: the old frame write carried the answer from A into the saved Q slot, so simply deleting the write left Q holding whatever it happened to hold. Services that answer by calling something were fine - Q already had it - and services that set A directly silently reported success for every failure. cosmosCwd is what noticed, by saying "cannot go there" about a directory that was there. Sixteen handlers move the answer into Q now. Seven MVQA went with it. They copied Q into A so the frame write could carry it; SRET puts A back, so they moved a value nobody would ever read. |
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Anachronaut
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cd5f548736 |
Move the opcode map: nothing in 0x0X, and room for a return variant
Three blocks move and nothing else changes. Branches take 0x60, subroutines take 0x70, and the ALU moves up into the 0x10 block the two of them used to share. Order within each block is preserved exactly - this relocates them, it does not rethink them. WHAT IT BUYS IS AN EMPTY 0x00 TO 0x0F. Program Memory that was never written, or a load that stopped part way and left zeroes in its tail, used to read as a long run of ADDs: the machine carried on through them, arrived somewhere unpredictable, and whatever broke there was a long way from the byte that caused it. Now it faults where it is met: Fault: 0x00 at Program Address 0x0004 is not an instruction. That is the address of the byte after the last real instruction, which is the difference between a diagnosis and a search. Reserving the whole nibble rather than just 0x00 means a run into blank memory faults wherever it starts rather than only when it lands on the right byte. runOffTest records it, and the block is left empty for whatever turns out to want it. The other half is room: branches and subroutines had filled 0x10 to 0x1F between them, so a service return that keeps Q and DP3 had nowhere to sit next to its family. It has 0x76 waiting now. Five places wrote an opcode down that the scripted remap did not reach, and four of them were found by tests rather than by looking: - secondPass.c lists which opcodes take an address, and firstPass.c knows SWI by number. Missing those made XOR read as a branch. - Asm.asm knows SWI by number too, being the other assembler. Missing it made the native and host assemblers disagree byte for byte, which is exactly the check that exists to catch a thing known in two places. - loaderTest.asm carries a hand written payload, and its RETI was 0x19. To the assembler those are numbers and to the program they are data, so nothing but running it could notice. It says so in a comment now. - The Assembler Manual prints the bytes hello.asm assembles to, and two of them were branches. The monitor's recorded disassembly moved by exactly the bytes it should: 18 became 72 wherever SWI appears, with SETD and INIB untouched and every disassembled line still reading the same. |
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Anachronaut
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ce2a2cd7e6 |
Settle is a program, and a machine with no fallback still starts
The boot state opened a loop that could not be closed from inside: the machine said "settle it to try again" and gave you no way to do so. Settle closes it, in 349 bytes. A PROGRAM RATHER THAN A SHELL WORD. The shell is for the things that cannot be done without it, and this is not one - it reaches the system through SWI like anything else, which means it can be replaced, left off a disk, or called by whatever comes to call programs in turn. That last one is the point: a shell word is not callable by anything. Two services for it. osBootState answers in Q, and a machine with no disk answers settled, because there is nothing there to be unsettled about. osBootSettle puts it back. SETTLING IS THE ONLY WRITE A PROGRAM GETS - marking a start as trying or fallen back is the loader's business, and a service that let a program claim either would let it lie about something the loader has no way to check. And a hole the tests walked into, which was mine rather than theirs. With no fallback configured, a failed start left the machine unable to start at all: the mark said do not use the system, and there was nothing else to use. That turns "the last start failed" into "no start is permitted", which is worse than the problem the mark was added to solve. With nothing to fall back to it now tries the configuration again and says so - a failure that was passing recovers, and one that is not leaves the machine exactly where it would have been without any of this, which is the most that can be promised when there is only one thing to start. docs.sh caught both new services having no row in the services table before anything else did. |
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Anachronaut
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dc74149321 |
B4: the disk remembers whether the last start arrived
The loader marks the superblock before it hands over and the system clears the mark when it reaches its prompt, so a system that crashes on the way there leaves it set. The loader finding it still set next time is how a machine that will not start says so to the only thing in a position to do anything about it. Without that, pointing boot.cfg at something that dies before the shell is a machine that can never be told anything again - the shell is the only way to change the file, and the file is what stops the shell from starting. Three states rather than two, and the third is the one worth having: 0 settled the last start arrived; use the configuration 1 trying handed over, and nothing came back to say it got there 2 fell back a try failed and the fallback was used, until settled With only 0 and 1 the machine alternates for ever: fall back, reach a prompt, clear the mark, retry the broken system, crash, fall back. State 2 stops that. A system known not to start is not tried again until somebody says the situation has changed. REACHING THE PROMPT IS A DELIBERATE THRESHOLD. It is not a claim that the system works - a shell can be reached by something broken in every other way. It is the point where a person can type, which is exactly what the fallback exists to give back: anything wrong past there is fixable from the prompt and nothing wrong before it is fixable at all. The routines live in sbfs.asm because both the loader and the system read and write this byte, and two pieces of code with their own idea of where a byte lives is what this format has two implementations and a byte for byte comparison to avoid. And the trap this system documents in its own manual caught me anyway: the first version handed the state back in A, which CALL restores, so every read got whatever the caller happened to be holding. It comes back in memory now, and the comment says why. Three disks differing only in the state on them, so the tests read as three consecutive starts of one machine while none depends on another running. |
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Anachronaut
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546f336823 |
Configuration files, and boot.cfg as the first of them
One setting to a line: a key, a space, the rest of the line is the value. A semicolon starts a comment. The format was noticed rather than designed - textSplit already cuts the first word off a line and leaves the rest, and textSame already insists two strings end together, so reading a setting is those two routines and a loop. It is also what the shell reads, which makes a configuration line a command line the machine reads instead of a person typing one. The format was chosen by asking what the BOOT LOADER could manage, because it is the worst case in every direction: a few kilobytes, no operating system to report to, and if it fails the machine does not start. Two formats would be worse than one and the loader cannot have the richer one. CONFIGURATION IS ADVICE. A missing file, a missing key, an unusable value, a line too long to read: all of them mean use the default and none is a failure. BUT QUIET IS NOT SILENT - a setting somebody meant, which did not take effect, says so. That was the user's addition and it is the better rule: the default alone leaves the only symptom being that the machine did not do what somebody asked. So two routines. cfgGet reads and says nothing, because reading three settings should not report one bad line three times. cfgCheck reads the file once and reports, and is handed the caller's list of keys - whether a key means anything is the only part of this a shared reader cannot judge. /System/Boot/ holds the boot files, and stage two reads boot.cfg for what to start, with a fallback to try if it does not work and a name compiled in for when the file says nothing. THE TEST FOUND A REAL BUG, and it is the interaction I would not have thought to look for. First-match-wins met an empty value: a file with system system /System/Boot/bare.bin matched the first line, handed back nothing, and the machine tried to start a file with no name while a good setting sat underneath. An unusable value is an absent one - which is what "configuration is advice" says, and this is where it earns its keep. cfgBare starts an image with no operating system in it at all, which is what loading an ordinary boot image buys: a program wanting the whole machine is a file like any other, chosen the same way the system is. Three disks differing ONLY in boot.cfg, so each is a test of the file rather than of the machinery under it. |
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Anachronaut
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c312853f8e |
The machine starts itself
stage two CosmOS > saved it read it back, 22 bytes: Stage one hands over to stage two out of a boot slot; stage two mounts the filesystem, finds /System/cosmos.bin, takes the image apart and places its code, its data and its vector table, and jumps to the entry point the vectors named. Nothing placed memory for it. What it loads is an ORDINARY BOOT IMAGE, the same SPBT file the emulator has always been handed. That was the user's call and it is the whole trick: a second stage that loads the machine's normal image format is not a boot-specific mechanism, so bare metal SplitBit stops being a special case. A program wanting no operating system under it is just an image, written under CosmOS like any other, and startable because it is a file. Three things in it worth knowing: - THE ENTRY POINT IS CAUGHT ON ITS WAY PAST. Program Memory cannot be read back, so the boot vector cannot be looked up after being installed; the vector loop notices the one addressed at 0xFC00 and keeps it. - A missing "VEC" is not a fault. An image written before vectors existed simply ends after its data, and then the entry point is zero, which is what every such image has always relied on. - Feature flags that are set mean an image asking for a machine this may not be, and the honest answer to a request that cannot be understood is to refuse rather than to run it anyway. The test records that the system WORKS afterwards rather than that it started. A loaded program running is what says the vector table arrived, because a program reaches the system through SWI and nothing else; the file written and the directory entered say the filesystem and the console came up with it. A second disk has a boot slot and nothing to start, and says so rather than jumping somewhere. |
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Anachronaut
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82adeeb193 |
A boot payload can arrange its own Data Segment
Stage one places Program Memory and nothing else, because knowing where a payload's data ends and its code begins would mean knowing a format, and knowing formats is what ROM must do as little of as possible. But the real second stage needs a Data Segment: sbfs.asm has variables and a string it compares against. The answer needs nothing new. A loadable image is written into the slot as code followed by data, so the data image is already in Program Memory just past the code - and the payload's first instructions blit it down to where it was assembled for. Proved by slotData.asm, which prints from a string it placed itself. The padding is the part worth recording. The blit needs a length and the assembler will not work out the difference between two labels, so the segment is padded to a round number and that number is what gets copied. The first draft padded to 257 and copied 256, and the byte that did not arrive was padding, so it worked by luck. It is exact now and says why. This is the shape the user asked for and it goes further than the mechanism: the second stage becomes a loader for the machine's ORDINARY image format rather than for anything boot-specific, so bare metal SplitBit stops being a special case. A program that wants no operating system is just an image, developed under CosmOS like any other, and selectable at boot because it is a file. |
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Anachronaut
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d07b23f90b |
Rung 2: the machine starts itself off a disk
Stage one exists and works. It is 330 bytes of program and everything it knows is a thing that will be true forever: which port the disk is on, that a SplitBit disk begins with its own name, and where two numbers sit in that first block. Not what a file is, not what a directory is, not that SBFS has versions. It reads the live boot slot into Program Memory, jumps to the first byte, and prints one character and halts if there is nothing there. It is an ordinary boot image for now, so the whole chain runs on machinery that already exists and the emulator has not been touched. Nothing about it changes when it moves into ROM except who puts it in memory. SplitDisk gained "boot" to write a slot and "bootslot" to choose one, kept apart on purpose: writing a slot and starting from it are different decisions, and joining them would make every write a commitment. A slot is always written WHOLE, because one still holding the tail of what was there before is one whose contents depend on its history, and stage one reads all of it without knowing where the file stopped. Three recorded tests, and the pair is the point: two disks differing only in which slot the superblock names, with payloads that say different things. One prints "booted" and the other does not, so this is a test of CHOOSING a slot rather than a test that some bytes were read. The third boots a disk with no boot area and gets the one character a ROM has room for. Eight more host checks, including that a slot is padded whole. Two things worth recording. The first draft used #Align to put the scratch buffer at 0x8000 and produced a 33K file - thirty two kilobytes of zeroes in something meant to be a ROM. It is an address, not storage, which is exactly what the assembler's own scratch map exists to say. And SplitLint caught the second in code written an hour after the baseline that catches it. In the blit set-up, RSTA writes a source address of zero and then RSTA writes a bank number of zero - two unrelated quantities that are equal by accident, in the most safety critical file in the repository. It is marked with a reason rather than removed. |
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Anachronaut
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9c144469b4 |
Take the SplitLint findings that are one operation, leave the rest
Twenty four more sites, and the interesting part is which ones were left alone. A rule emerged while reading them and it held all the way through: apply where the repetition is INSIDE one operation, skip where the author's own structure says it is a new thought, and never where two equal values mean different things. Taken: - Five registers reassigned to a value they already held, where both are the same quantity: two masks in one expression in Snake, two spaces printed by the monitor, both halves of block zero in waitTest, and a RSTA in Pour that the very next instruction overwrote. - Eighteen SETDs that reload a pointer inside one operation - a store back into the variable just read, or an INCD stepping to the second byte of a two byte value. Those read correctly without the reload. - sbfsNext, which branched to the label on the line below it. Left, with reasons that are the useful part of this: - Eight registers where the same number means two different things. CosmOS and the loader set A to 1 for a blit command and then to 1 again for a bank number; Asm compares a type against 3 and then a status against 3. Removing those couples one quantity to another that is equal by accident and would part company silently. - Ten RSTAs that open the RSTA/RSTB/CCF/ADD "return zero" block. The redundancy is what makes that idiom self contained; taking it out makes the return value depend on the line above. - Eleven SETDs that begin an arm of a comparison chain. Each arm loads, compares and branches, and they get reordered - the repetition is the reason a new arm can be dropped in anywhere. - Twenty five SETDs separated from their pointer by a blank line or a comment, which is the author saying a new thought starts here. - Two CCFs before arithmetic, which this codebase writes unconditionally. - Three redundant branches in test programs whose recorded output includes addresses, where three fewer bytes moves what the test demonstrates. Nine recorded outputs moved and every one is a size in a listing or, for Life, five more generations inside the same cycle budget. Behaviour is unchanged everywhere: cosmosSnake and cosmosEdit pass byte for byte while Snake loses eight bytes and Edit twelve. CosmOS is 10,902 bytes of program against 10,937, and the native assembler 12,173 against 12,183. The CosmOS README's size for Edit moved twice in one sitting, and this morning's check caught it both times - which it could not have done before that claim was reworded to name what it was about. |
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Anachronaut
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e1273337c4 |
Two mechanical fixes SplitLint found: MVQA, and RSTA for zero
Twenty four places moved Q into A or B by pushing it and popping it back. That is four bus cycles and two bytes to do what MVQA does in one of each, and several of them are inside loops - Life, the calculator, int8. Nineteen more loaded zero with INIA 0d0 where RSTA says the same thing in one byte. Both are equivalent at the CPU rather than by assertion: RSTA and INIA both leave Status alone, and PSHQ followed by POPA nets to A = Q with the Stack Pointer where it started. The one difference is that the pair leaves a copy of Q in memory just below the Stack Pointer and MVQA does not, which nothing here reads. Five recorded outputs moved and every one of them says the change worked: - 16x16Life fits five more generations into the same cycle budget, the first 457 lines identical, because the loop got cheaper. - Life.sbx is 1409 bytes rather than 1411, in three tests that list it. - Edit.sbx is 1995 rather than 1996. That last one broke a check I added this morning, and the hole is worth recording: the CosmOS README's claim about Edit's size did not have the word "Edit" on the same line as the number, because the subject was in the sentence before, so the check that measures quoted sizes skipped it silently. The sentence now names what it is talking about, which makes it both checkable and clearer, and the check fails on a wrong number there. Comments on either half of a replaced pair are carried onto the instruction that replaces them, so nothing anybody wrote was lost. |
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Anachronaut
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8f4cc5878d |
Repair a table cut in half, and measure the numbers that had drifted
The README's emulator options table was split by forty lines of prose: two rows, then the whole discussion of the cost model, then five more rows with no header above them. Markdown renders that second half as something other than a table, so three of the seven options were not being shown as options. The rows are back together and the prose follows them. Four numbers had gone stale, in three different ways, and none was noticed: - "Five more scripts run alongside it" - there are six, and lint.sh had no bullet saying what it was for. - "rebuild all three tools" - there are four. - Files.asm quoted at 645 bytes in two places; it is 665. - Edit quoted at 1,983; it is 1,996. The last two are the most quotable sentences in the CosmOS README and the least likely to be rechecked by hand: the programs kept being made better and the sentences about how small they are stayed where they were. So docs.sh measures all four now. It counts the scripts in Tests/ that are not the driver or the disk builder and checks the README says that many and explains each one; it counts what the makefile's all target builds and checks the tool count in both phrasings, which took two attempts because one sentence says "the four tools" and the other "all four tools"; and it assembles every app the CosmOS README quotes a size for and compares. Each check was confirmed by making the fact wrong and watching it fail. WAIT also added a second kind of cycle this morning and the cost model section still described only one. It now says what an idle cycle is, why the two are counted apart, and what that distinction is FOR - a machine that slept through a slow disk and one that spun on it take the same elapsed time and print the same characters, and only the split tells them apart. The duplicated sentence about pipelining is gone; it was said twice, eleven lines apart, in nearly the same words. |
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Anachronaut
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2b079324ae |
Add SplitLint, and let it be told when something is deliberate
SplitLint reports valid assembly that has a shorter direct expression: zero loads that could be RSTA or RSTB, Q moved through the stack where MVQA would do, self-cancelling push and pop pairs, assignments overwritten before use, unreachable fallthrough, one-byte pointer moves that could be INCD or DECD, a branch to the label directly below it, a SETD reloading an address the pointer already holds, and branches whose carry is known. Its model is deliberately local and conservative: every label and every directive forgets all known state, so a claim only ever lives inside a straight-line region. It knows the calling convention - CALL forgets DP3 and keeps the rest, RCAL and SWI forget everything - and it shares assembly.o with the assembler, so an added opcode cannot leave it holding a private copy of the instruction table. 260 warnings across the corpus, of which three were wrong in the way that matters: branchTest.asm and interruptFlagTest.asm exist to check that a branch whose carry is known behaves correctly, so a diagnostic saying the outcome is known is exactly right and exactly unwanted. A line whose comment says "splitlint: <reason>" is now not reported on. THE REASON IS REQUIRED and a bare marker is refused, because a suppression nobody explained outlives whatever made it necessary. Suppressed warnings are not counted, so --fatal-warnings does not fail on one, and the number of them is printed at the end so the claim is visible rather than silent. Tests/lint.sh checked a TOTAL: twenty three warnings expected, twenty three found. That number stays right while the thing behind it goes wrong - a rule that stopped firing while another fired twice would pass, and so would a rule reporting at the wrong line. It now checks which warning came out and at which line, that nothing else came out, and that the four lines meant to stay quiet did. Confirmed by breaking one rule's message and watching it name that rule: the old assertion passed the same sabotage, because the warning still fired and the count never moved. Written with the user while I was away; my part is the suppression mechanism, the harness rewrite, and the three marks in the test programs. |
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Anachronaut
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c216c83e12 |
The filesystem waits for the disk instead of asking it repeatedly
sbfsWaitDisk spun on the status port. Read ahead had already hidden about
three quarters of the latency, and what remained was still 11.5% of Type
over a 14K file on a ten thousand cycle disk - all of it memory traffic
spent finding out that nothing had happened yet.
It tests the port first and only waits if the disk is still busy, and that
order is the whole of what makes it safe: the disk raises its line when it
finishes, so a disk that finished in the gap between the test and the WAIT
has its line standing already and the WAIT does nothing rather than
sleeping through the answer. No handler and no vector - the shell keeps the
Interrupt Flag down, and a WAIT wakes on a line whether or not anybody
means to answer it.
Printing a 14K file, by where the cycles go:
cycles a block total bus waiting
0 922,570 922,570 0
2,000 946,474 922,702 23,772
10,000 1,042,474 922,702 119,772
The bus column stops moving. What the program costs in memory is now the
same whatever the disk does. On this emulator nothing observable changes;
on hardware it is a CPU standing out of the way of the memory controller
rather than competing with it for every one of those 119,772 cycles.
The first version cost 660 cycles more at latency zero because it read the
status port again on the way out. AND writes to Q and leaves A alone, so
the status was already there - which is what the original said in its own
comment, and what I stopped believing while rewriting around it.
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Anachronaut
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c3188ed657 |
Seventy becomes seventy one: a machine that can wait
HALT is terminal - stepCPU returns at once when the Halt Flag is up, so a halted machine does not execute, service devices, or take an interrupt - and that has to stay true, because every test ends with a halt and "halted" is how a program says it has finished. The consequence was that SplitBit had no way to wait at all. Every wait was a spin, and a spin is bus traffic: 11.5% of Type over a 14K file on a disk of ten thousand cycles, after read-ahead had already hidden three quarters of the latency. WAIT is 0xFE, one byte, no operands, sitting under HALT where the instruction that almost stops the machine belongs. Three decisions in it: - A line already standing means there is nothing to wait for, so WAIT does nothing. That is what makes test-then-wait race-free. - Any line ends the wait, masked or not, so a program can sleep on a device it has no handler for and read its status afterwards. Masking says who answers a request, not whether it happened. - A line that wakes the CPU without being dispatched is taken down by the WAIT. Left standing it would be found by the next WAIT, which would return at once - the program would spin exactly as before while looking as though it slept. Waiting is NOT a Status bit, and that is the trap avoided rather than a gap: Status rides into the interrupt frame and comes back out, so a machine interrupted mid-wait would return from its handler still waiting, and wait again for what it had already been given. An internal field instead. Idle cycles are counted apart from bus cycles and the halt line says so when there are any, which is what makes the difference observable at all - with the line-clearing removed the total moves by ONE cycle, 20,100 against 20,099, and only the idle half changes, halving to 9,976. A test on totals could never have seen it. Tests/terminal.sh asks that question, being the file for things a recorded output cannot see, and fails with the clear removed while "both reads finished" still passes. Three collisions, all found by building it: - 0xFE was the assembler's "not an instruction" sentinel. getOpcode now answers a negative NOT_AN_OPCODE, which is outside the range of every possible answer instead of inside the unused part of it. - 0xFE was also what faultTest and faultResumeTest executed to provoke a fault. They now use 0xFD and say why, because they did not fail when it became an instruction - they HUNG, having started sleeping instead. - Keys.asm has had a label called "wait" for a year, and mnemonics are matched uppercased. What that reported was "Branch without label" at the BRQ thirty lines away. The assembler now refuses a label that is already an instruction, at the label, by name; every instruction added takes a word out of the space of label names, so this will happen again. |
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Anachronaut
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6b41354f8f |
Delete a comment describing a design that was removed, and check the rest
Two comments in the native assembler survived the changes that made them false, and both are the kind that misleads rather than merely ages. Asm.asm still explained an eighteen kilobyte buffer that the whole output had to fit in "because a file is written in one call and there is nowhere to put half of one" - which stopped being true when the assembler learned to stream, and the variable it described, ImgRoom, does not exist any more. It was sitting in front of the comment that replaced it, so the paragraph a reader met first described the design that had been taken out. Replaced by what is actually there: no limit but the disk, one block at a time through a window in scratch. scratch.asm said the system keeps below 0x1000 twelve lines above the paragraph explaining that the system's half of Data Memory was doubled to 0x1FFF. A stale number next to its own correction is worse than a stale number alone, because which one a reader believes is a coin toss. docs.sh now checks both of the facts scratch.asm asserts about the machine around it: the floor it claims the system keeps below, against the CosmOS README, and the address its buffers start at, against where the assembler's own data actually ends. Neither is enforced by a line of code anywhere - the map is a comment, deliberately, because reserving the buffers would put 22K of zeroes in the file and the assembler could not load itself - so a check is the only thing that can hold them. Both fail when broken; the second reports the exact overlap. |
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Anachronaut
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ce0f18f4ef |
Refuse a directory whose last entries cannot be named as a parent
A parent is an entry index PLUS ONE in two bytes, so entry 65535 has no parent number: adding one wraps to zero, and zero is the root. Eight entries to a block, so 8192 directory blocks reaches it and SplitDisk formatted that happily. It does not fail by refusing, which is why it was worth chasing rather than reasoning about. Reproduced on a disk built for it: mkdir /deep/child, with /deep at entry 65535, printed 'Made "/deep/child" as entry 0' and put child in the ROOT. Listing /deep then showed nothing, because the search is for a parent of 65536 and the entry carries zero - so the same mkdir succeeded again, and again, and five entries called /child piled up in the root. Duplicate names in one directory are the one thing rename refuses outright, on the grounds that a search answers with whichever it meets first and the rest can never be reached; this manufactured them one per attempt. 8191 blocks is the most, giving 65528 entries. Refused when formatting and again when reading, in both implementations, because a disk claiming more was made by something that never checked. On the machine only the high byte of the count has to be looked at: anything from 0x20 up is too many. Three checks, all of which fail with their guard removed. The machine's disk claims the size rather than having it, so the test image is 64 blocks that lie rather than sixteen megabytes that do not - mounting is refused at the geometry, which is read out of block 0. |
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Anachronaut
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2b5506ee70 |
Stop the prompt writing off the front of its own buffer
The prompt is the working directory's path, worked out each time by walking the chain of parents up to the root. The names arrive deepest first, so they are written backwards from the end of a 127 byte buffer - and nothing bounded that walk. Nothing bounds the depth either. A path given to one operation is capped at 95 characters and a 22 character name, but "mkdir a" and "cd a" are each far inside that and can be repeated forever. Six directories of 22 characters is 132 characters of path, and at that point the walk wrote down past the front of CwdText and into what the assembler had laid out below it: the shell's own command names. ExitName sits five bytes under, so the word "exit" went first and the shell stopped recognising the command for leaving. Measured, not deduced: fine at five levels, gone at six. The walk now counts the room it has left, byte by byte, and stops. What is already written is the DEEP end of the path, which is the end worth showing, so it is cut at the front and three dots say so - out of three bytes held back from the count, so there is always somewhere to put them. Twenty levels deep the prompt shows the last five and every command still works. cosmosDeep records that, and records it by running help, cd and exit from down there rather than by looking at the prompt: a wrong prompt is cosmetic, and this was writing into other variables. It fails with the bound removed. The tree is built by SplitDisk because a path that long cannot be given to mkdir in one piece - which is the same fact that makes the depth unbounded. The three path limits are written down in the README now, including which one actually binds. The other two do not: the longest path on a full install is 21 characters. |
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Anachronaut
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ce8fb721fe |
Say a temporary is one in the entry, not in its name
Saving something that already exists writes a temporary, deletes the original and gives the temporary its name, so that nothing is lost if the writing fails. The temporary was told apart from a real file by being called sbfs.part or sbfs.out - and those are legal names. Starting a save deleted whatever answered to one as stale scratch, so saving anything at all in a directory destroyed your own file of that name there, silently. Flag bit 0x04 now says it. The property is not in the contents - the same bytes become the finished file the instant the rename lands - so it belongs in the entry, which is the thing the commit changes. sbfsCreateTempAt is the door temporaries come in by, the commit writes the flags flat along with the name, and cleanup wipes what it finds only if the entry says it is ours. Anything else stops the save instead. The bit is also the recovery. Both listings show an unfinished write rather than sizing it, because the size in the entry is the room that was asked for and not what was written: "<unfinished>" from dir, and a line from SplitDisk saying the blocks are held and a rename brings the data back. That was the gap in what the last commit documented - the data survived a crash and nothing would show you where it was. Four new agreement checks, three of which fail with the guards removed. The fourth needed rebuilding first: both tests started on one disk, and the first save ate the sbfs.part that was the second test's SOURCE, so the copy failed for want of a file, never opened a stream, and passed while reporting on nothing. A disk each. The fifth check forges the wreckage by setting the flag on a finished file, since nothing here can crash a save half way through. No version bump: a committed file never carries the bit, so a disk this writes is byte for byte the disk the old code wrote, which the whole-image comparisons confirm. Only the wreckage differs, and older code reads that as an ordinary file - which is what it did before. |
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Anachronaut
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9e2aa0122e |
Say what a safe save actually promises, and where it stops
Both sbfsSaveFile and sbfsStreamDone write a temporary, delete the original and rename the temporary onto its name, and the README explained why that order and not the obvious one. It never said what the resulting guarantee is, which invited the stronger reading: "safe save" sounds like it survives anything. It survives everything that goes wrong while it is running - no run long enough, no free blocks, a refused write, a name that turns out to be a directory, a writer that gives up - and in all of those the original is untouched. It does not survive the machine stopping, because the commit is two block writes with a gap between them: stop there and the old file is gone and the new one is still called sbfs.part. The bytes are all present and one rename by hand recovers them, but nothing does that on its own. Written down in the README beside the ordering it qualifies, and at both commit points in sbfs.asm, where a reader is when the question occurs to them. Closing the gap wants a journal or a second directory, which is a lot of disk for two writes; a boot-time consistency check is the cheaper answer if it ever matters, and it would want temporaries flagged in the entry rather than recognised by name. |
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Anachronaut
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aa7bdc6acd |
Check the memory map against itself, not only against the code
The CosmOS README's Data row gave the system 0x0000-0x3FFF and a loaded application 0x2000 and above: two columns of one row that cannot both be true. Program was doubled to 0x3FFF when CosmOS outgrew its first map and that number was copied into the Data row as well, where the answer is 0x1FFF. docs.sh measured both segments against the CosmOS column and passed the table anyway, because it never read the column beside it. A number checked against the code and not against the number next to it is still unchecked, so it now reads both and compares them - and compares two further copies of the same fact that had gone stale on their own: the minimal application in the README, still based where applications lived before the doubling, and the map cosmos.asm opens with, which somebody reading the system reads before they read the README. Each of the three checks was confirmed by breaking the fact and watching it fail; the first reproduces exactly the text this commit removes. While in that header, the command list said five commands and CosmOS has eleven and a search path besides, and "dump is next" outlived the monitor. |
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AnachronautandClaude Opus 5
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db3d349da8 |
Read the next block while the program is busy with this one
A file is read front to back, so when something asks for a block, the one after it is almost certainly wanted next. sbfsReadOne asks the disk for it straight away and hands back the block that was wanted - so the transfer happens while the caller is busy, and the waiting is mostly over by the time it comes back. Printing a fourteen kilobyte file: 1,064,498 cycles at two thousand a block becomes 976,882, and 1,576,562 at ten thousand becomes 1,032,889. The second figure barely moves between those - seven per cent from an instant disk to a slow one, where without it the same change costs sixty eight. A machine that reads ahead stops caring very much how fast its disk is. NOT FOR DIRECTORY SEARCHES, and that was tried first and thrown away. A scan stops the moment it matches, so the block it would read ahead is one nobody will ever look at - a transfer to fetch and another wait to throw away. It was nineteen per cent SLOWER on a lookup at ten thousand cycles a block. Reading ahead is a bet that the next block is wanted, and a search is exactly the case that hopes it is not. The scan loop is untouched. Three per cent is what it costs when the disk is instant, which is the bookkeeping with nothing to hide behind it, and the default. The disk has one buffer, so the only way to know what is in it is to remember what was last asked for. Every read records that; a write clears it, because a write fills the buffer from memory and no read asked for what is in it. Getting that wrong would blit whatever happened to be there and call it the block somebody wanted. The read ahead is bounded by the file's own length, so reading the last block does not fetch whatever follows the file on the disk - which belongs to somebody else and would be paid for twice, once to fetch and once to discard. It cost one bug, and an instructive one: the next index was worked out by stepping SbfsIndex, which is the CALLER'S and is still wanted after the return - handleFileBlock compares it against the file's length to see whether this was the short last block. Every block reported the wrong number of bytes, and the output of Type skipped five lines in the middle. It has a place of its own now. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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d4cba36c5e |
Devices that take time, and a filesystem that waits for one
The disk's status has always had a bit meaning "still going", and the header beside it has always said to honour it. Nothing did, because nothing could: the host finished the transfer inside the instruction that asked for it, so the bit could never be seen up and asking about it was asking about something that cannot happen. --disk-cycles gives it a latency. The command is still checked at once, because a refusal is not work - a block that is not there fails before any head moves - but the transfer is remembered and done when the machine has run that far. Until then the buffer holds the block BEFORE this one. That last part is the point. A program that does not wait gets the wrong bytes rather than an error, which is the failure the bit exists to prevent and the one that would never have shown up. With a latency of two thousand, CosmOS could not even mount: sbfsMount reads block zero and looks straight at the buffer. deviceTick is the general shape rather than a disk feature. Called once per instruction with the machine's clock, it lets anything whose moment has come finish - which is what a display that refreshes, or a port that waits on the host, would want in exactly the same way. The filesystem watches the bit now, in one small routine reached with RCAL. That is not decoration: what it hands back is the settled status in A, and CALL puts A back the way it found it, so an ordinary call cannot carry the one thing this exists to carry. Two bytes of Stack rather than ten, in a routine that runs on every block the machine ever touches - the first place in the system where the new call is the right one rather than merely a cheaper one. The manifest takes a @N after a disk, the way it already takes :ro, so a test can ask for a slow one. cosmosSlowDisk lists a directory at two thousand cycles a block and gets the same listing as everything else, which is the whole assertion: a filesystem that did not wait would print nonsense rather than fail. Zero is the default and every other test runs at it. What waiting costs, on a directory heavy run: 229k cycles at zero, 275k at five hundred, 415k at two thousand, 1.16M at ten thousand. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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54f5cfe8a4 |
Add Copy and Compare, which stream in both directions at once
Copy joins the read and write streaming services: source and destination are both larger than Data Memory while the program owns one block. Compare reads two files through separate blocks and ignores the bytes past a short final block, which belong to neither file. Between them they exercise empty, exact-block, part-block and 84,000 byte files, and the host extracts the copy afterwards so that two native programs agreeing with each other is not the only oracle. Written by ChatGPT, as their headers record, along with the agree.sh section and the manifest entry that drive them. THIS SHOULD HAVE COME FIRST. The commit before it staged whole files rather than the hunks it meant, so its manifest already names these two programs while their source was still untracked - that commit will not build on its own. Left in place rather than rewritten, since the pair is right and only their order is wrong. NOTES.md is their review of the streaming work. The first item in it is fixed by the commit before this one; the rest are still open. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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a7d3e09d94 |
Refuse a streamed file that commits more than it reserved
osFileStart sets an extent aside and osFileWrite refuses a block index outside it, so writing off the end was already barred. Committing a larger size was not, and reaches the same neighbour by simply claiming it: a directory entry is the only record of what a file owns, so an entry claiming a block it was never given owns it, and so does whatever owned it before. Both files then look perfectly well formed. The free count went backwards past zero on the same path. Found by ChatGPT's review of the streaming work, in NOTES.md. I had bounded the index because writing off the end was the obvious way to reach a neighbour, and had not noticed that the other end of the same reservation was open. THE SIZE IS COMPARED, NOT THE ROOM IT TAKES UP. One block and a tail occupies exactly what two whole blocks occupy, so bounding the blocks alone would let a file reserve the first, commit the second, claim no block it was not given, and still report two hundred and forty six bytes that were never written to it - whatever the disk had there before. Checked before anything is touched, which is why the temporary is found twice. The old file is deleted a few lines down and a refusal after that point would have destroyed the thing it was protecting. AND IT CAUGHT A REAL ONE IMMEDIATELY. The assembler reserves the file plus room for its vectors, and asked for four bytes per vector DECLARED - which looks like a safe bound and is not, because a device is declared during the SECOND pass, in the line that implements it. A program with a device installs a vector that was not counted when the room was measured. CosmOS reserved 14,163 bytes and committed 14,167, writing four bytes past what it had been given on every build since S2. It landed inside the last block it owned, and would not have if the boundary had fallen four bytes earlier. It reserves against the vector table's LIMIT now, which cannot go stale whenever things are counted. Claim.asm is the program that tries it: reserve one block and a tail of ten, write them, then tell osFileDone the file came to two whole blocks. The refusal and the honest commit that follows are both recorded. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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af0360128b |
Sixty four instructions becomes seventy
The six settled back on the twenty fourth, built now. RCAL and RRET are a call that puts nothing back. CALL restores A, B and Data Pointers 0 through 2, which costs ten bytes of Stack and is why a subroutine here can only hand anything back through Q, DP3 or memory. RCAL costs two and restores nothing, which is what a short leaf routine wants and is unsafe in exactly the way the name says. They are a pair because the frames are different sizes: returning from one through the other walks the Stack to somewhere that was never a return address. That was the user's correction to the original proposal, which had a raw call and no raw return. DPUA and DPDA offset a Data Pointer by A; DPUW and DPDW by A and B together, most significant first. DPUP and DPDN take a byte written into the program, so moving a pointer by something just worked out meant storing it and loading it back. Down as well as up on symmetry grounds, which was also the user's call - the argument against it came from counting uses in a corpus written under the constraint. The opcodes sit where they belong: 0x16 and 0x1E immediately below CALL and RET, and 0x4E through 0x51 at the end of the Data Pointer family. All six fit shapes that already existed, so instructiontable.py needed only set membership and both machine side copies of the table regenerated from it unchanged. Checked at every level it exists at: the emulator runs them, the host assembler encodes them, the monitor disassembles all six with the right lengths, and the assembler that runs on the machine builds a program using them byte for byte identically to the host - and that program runs. The recorded test measures what the two calls COST as well as what they put back, because an RCAL that quietly did what CALL does would still return to the right place. It does not survive that: returned through RRET, it hangs. docs.sh can read a two word number now. The count of instructions taking a Data Pointer went past twenty, and the pattern only allowed one word, so the check would have reported that the manual had stopped saying it rather than that the number was wrong. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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00d896e3e7 |
Break shows registers it chose, not ones it inherited
Break left DP1 and DP2 alone, so what a stop printed for them was whatever the shell happened to have left there - which is a CosmOS address, which moves whenever CosmOS is touched at all. The recorded output had to be taken again four times in one day's work, every time for a value that is not this program's and that nothing should ever depend on. It sets all three of the pointers it owns now, rotated between the two stops so that every one of them visibly changes, the way A and B already did. DP3 stays as the system left it: it is where the program was entered, which is the one thing worth seeing here that this program did not choose, and it is steady because it is this program's own base. A demonstration of what the registers were should show registers somebody chose. Then every line of the record is being asserted rather than merely observed, and a reader can tell which is which. Checked both ways: sixty four bytes added to CosmOS's data no longer moves it, and reading the frame at the wrong offset still fails it. cosmosRun and cosmosMonitor move because Break is sixteen bytes longer and both of them list the disk it sits on. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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fb7b224bbb |
S2: the assembler writes the file as it makes it
The output image is gone. It was eighteen kilobytes and it is now one block of window, because the file was always produced in order and only ever needed to be written that way. Everything works in FILE OFFSETS now. A cursor is a two byte number counting from the front of the file, and since a block is two hundred and fifty six bytes, the block it lands in is the offset's high byte and the place within that block is its low one - so there is no division anywhere, and ImgWalk, ProgPut and DataPut needed no change but where they start. ONE WINDOW RATHER THAN THREE. The plan said three: one per segment, and a third for the block where the program ends and the data begins, which belongs to both. Fetching a block back instead makes all of that one case. The header is patched after every byte is out, the boundary block is written by both cursors, and both are simply revisits - a revisit is what fetching handles. osFileFetch is the service that allows it, and is the read side of the write. A run of bytes in one segment costs nothing extra; a switch between segments costs two block operations, and a source file has a few dozen switches and several thousand bytes. Two bugs, both a pointer meaning two things: putAt took the cursor to advance in DP2 and then wanted DP2 for the window's address. A call puts DP2 back the way it was AT THE CALL, so the step at the end moved whatever the last call had left there - the window walked off across memory while the cursor stood still. It goes in memory now, like the block did in S1, and for the same reason. The size the file is created at could not be right. How many vectors are actually installed is not known until the second pass has resolved their handlers, and by then the file must already exist to be written into - so Keys, which brings one vector, came out four bytes short. Teaching the first pass to count them meant teaching it about devices, and about a Boot line in a loadable program not being installed at all, which is two ways to disagree with the second pass about what a file contains. So osFileDone is told the size instead. A writer asks for as much as the file could possibly come to - the whole of it plus four bytes for every vector DECLARED, which no file can exceed - and says what it really came to at the end. The blocks it did not use go back to the free count. Asking for too much costs a moment; asking for too little writes off the end of a file. That is a better service for it, not a workaround. A writer that cannot know its size until the last byte is the ordinary case, and it is exactly the case this whole rung exists for. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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9f7dffdeca |
S1: the write side learns to stream
osFileStart, osFileWrite and osFileDone are the mirror of osFileInfo and osFileBlock. A program can now write a file it never holds: Pour writes twelve blocks and a tail while keeping 256 bytes of it at a time, and the host tool reads all 3,112 bytes back with every block where it was put. ONE WRITE IS OPEN AT A TIME AND COSMOS HOLDS IT. Reading needs no state - a name and an index are the whole question - but writing safely does, because the new file has to exist before the old one is thrown away and something has to remember which temporary belongs to which name. Keeping that here means the careful order is written once instead of in every program that streams. Nothing already on the disk is touched until osFileDone, so a disk without room says so while the old file is still there. That is stronger than osFileSave can manage, where the size is only known once the caller has every byte in hand. osFileSave stays: Edit and Files hand over whole documents and have no reason to learn any of this. osFileWrite refuses an index past the end of the file, and that refusal is not politeness. Files are contiguous, so block nine of a three block file is a real block belonging to something else, and writing it would put one file's bytes inside another with nothing anywhere saying so. Checked both ways: the tail block is allowed and the one past it is not. Three bugs, all of them the same shape - a register or pointer used for two things at once: DP3 carried the block count in and was popped high byte first, which is the wrong way round from every reader in the system and made the count two hundred and fifty six times too big. sbfsStreamStart took the name in DP0 and then wanted DP0 for something else before it had read it, so it walked whatever it last pointed at and reported that it could find no room. sbfsStreamWrite kept the caller's block in DP3 across a find - DP3 being the pointer a return does not put back, which is exactly why the find uses it too. What went to the disk was whatever the scan last looked at. It goes in memory now, and the file is correct because every block says which block it is; a check on the length alone would have passed all three of these. Writing no longer finds the file for each block either. Nothing moves a file once it is made, so where it starts is settled when the temporary is created. That was not even slow - a scan stops the moment it matches - but it was a walk of the directory per block for an answer that cannot change, and it is 28 per cent of the cost of writing forty blocks. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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7cd5e34347 |
Two ceilings a hundred bytes apart look like one ceiling
The sixteen kilobytes taken back a moment ago all went to the output image, because that was the wall: 13,245 bytes of cosmos.bin against 13,312. Lifting it moved the machine straight into the next one, a hundred and eleven bytes away - the label names, at 8,081 of 8,192 - and the index was a hundred and eighteen entries from the same place. So the room is shared out rather than given to the obvious one. Names and index both double, and the output takes what is left, which is still four and a half thousand bytes more than CosmOS needs. LabLimit and LabRoom in labels.asm have to agree with the map in scratch.asm and are now said to. Worth recording how this was found, because it is the good case. The assembler STOPPED and said "no room left for label names: Mode, at line 3598" - a limit it checks, names, and points at. Every other ceiling this project has hit went unnoticed until something downstream broke: a program loaded over the shell, a path silently cut short, a file reported as itself less 65,536. A limit that announces itself is worth the handful of instructions it costs. The output's eighteen kilobytes are temporary. They exist because the assembler holds a whole finished file in memory before writing it, and the file is produced in order, so it could be written as it is made. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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ec56439d9a |
Take back the sixteen kilobytes the scratch map left behind
The assembler's buffers start at 0x8000, and the reason written beside them is that everything above its own data is free. That was true when it was written. The system kept below 0x1000 then; its data now reaches 0x1FFF, and the assembler's own moved from 0x1000 to 0x2000 with it when both halves of the memory map were doubled. The floor came up and the map stayed where it was, leaving sixteen kilobytes between the two that nothing touched at all. Starting at 0x4000 takes that back, with nearly four kilobytes of slack still in front of it and room for the assembler's own data to double before the two would meet. All of it went to the output image, because that is the buffer that is actually full. cosmos.bin is 13,245 bytes against the 13,312 it had, which is sixty seven bytes - the next thing added to the system would have made the machine unable to build it, and it would have shown up as a test going red rather than as anything explicable at the machine. The label table has room yet, so this is not the moment to share the space out evenly. This is the third time a limit here has gone unnoticed until something hit it, and the second where the cause was a number that stopped being true rather than one that was ever wrong. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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06bdbf7728 |
D5: move in, and give the assembler somewhere to look
The demo disk is three directories instead of thirty nine names in one list with cosmos.asm sitting between fileStream.asm and sbfs.asm: /Apps what you run /Source what you name to the assembler /Lib what those include The split is by ROLE rather than by which directory the host keeps a file in. Everything in /Lib is named by an #Include somewhere and by nothing else, which is what makes it a library rather than a source. THAT LAYOUT WAS NOT POSSIBLE UNTIL NOW, and finding out why is what this rung actually cost. An include on the machine was a bare name resolved where you stood, so every source that calls a service had to sit in the same directory as services.asm - which is every source worth having. The first arrangement of this disk put the examples in a directory of their own and none of them would assemble. So the native assembler has a search path: beside you, then /Lib. The same rule the shell already uses for a program it does not recognise, applied to the thing that reads source, and the same reasoning for it being two fixed places rather than a list - a list needs somewhere to live between one boot and the next, and there is no such place yet. It also brings the native assembler nearer the host one, which has searched -I directories since before there was a machine to run this on. The reader's per-file state grew from 293 bytes to 301, because the name it keeps is a path now and every block of a file is asked for by it. Six of those would no longer fit the room set aside, so the include list moved up a page. Both numbers are written down in two places on purpose and both were changed. dir said cosmos.asm was 17,460 bytes. It is 82,996. The size came out of the block count's LOW BYTE shifted up and the tail beneath it, which is sixteen bits, so anything from 256 blocks upward came back as itself less 65,536 - a plausible number, and wrong. Files that big say their size in blocks now. Printing the true figure wants decimal printing twenty four bits wide, which is a page of console.asm to say something nobody reads more precisely than "big". The Assembler Manual's line about SBFS being flat was the last thing in the repository still claiming it, and docs.sh now looks for that phrase and three like it in all four documents. Not a section that is wrong - one clause inside a paragraph that is otherwise right, which is the shape this kind of staleness takes. The duplicate puts are gone with the wildcard that caused them, so building the disk is quiet. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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da91a36d92 |
D4: the machine makes directories too
mkdir and rmdir are the machine's own now, and a file goes where its path says rather than always in the root. A disk can be organised without the host tool touching it. Everything below the surface works in terms of a directory and a name rather than a path. sbfsWalkParent splits the last name off, walks the rest, and hands back the two - and the separator stays on the end of the head, which is what makes one rule cover every kind of path: "/x" leaves "/", which is the root; "x" leaves nothing, which is where the machine already is; and "A/x" leaves "A/", which is neither and needs no special case to say so. Saving works in those two as well, and had to. The careful order a save uses - make a temporary, write it, delete the original, rename the temporary - only works if the temporary is made in the SAME directory as the file, because the rename at the end changes a name and does not move anything. Renaming to a path naming a different directory is refused for that reason, rather than quietly being a lie the disk goes along with. Three things this cost, all found by running it: mkdir Apps/Deep made /Apps/Apps. The leaf was worked out into SbfsWanted and then the head was walked - and walking goes through sbfsPathNext, which puts every name it meets into SbfsWanted on the way past. The head's last name landed exactly where the leaf was. It has somewhere of its own now. rmdir took a directory with something still in it, which is the one failure the whole design is arranged to prevent. Looking for children clobbered DP2 and rebuilt it from the buffer and the entry count with the subtraction the wrong way round, so the pointer walked off the end of the block and found nothing. The comparison goes through a CALL now, like the two beside it, and DP2 comes back on the entry because a RET puts it there. SplitDisk's "in use but not reachable from the root" line is what caught it. Refusing a name longer than twenty two used to read the twenty third character of a shorter one, which is somebody else's string. It is measured now. Tests/agree.sh is new and is the gate this rung was for: the same disk built twice, once with SplitDisk and once with CosmOS, compared byte for byte. The two share no code and only a written specification, and every field one writes and the other only reads is checked there and nowhere else - which entry a thing lands in, which block, what a directory's unused fields hold, the version, the free count. It caught a wrong parent immediately when that was broken on purpose. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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36ce9f6ccf |
D3: the machine knows where it is
cd moves it, dir lists the directory it is in, and the prompt says which one - but only when that is not the root, so a machine nobody has moved about on looks exactly as it always did and every recorded test that never says "cd" keeps its recorded prompt. A path beginning with a separator is measured from the root and anything else from where the machine is, so a bare name means a file in the current directory. NO PROGRAM HAD TO BE TOLD: the working directory lives in sbfs.asm beside the thing that resolves paths, because it is what a relative path MEANS. Keeping it in the shell would have meant either handing it down on every call or pasting it onto the front of every name, and the second of those is how a name that is already absolute gets ruined. Nothing stores the path. The working directory is an entry index and two bytes, and the text on the prompt is built each time by walking the chain of parents upward, writing names from the end of a buffer towards the front - which is the order they arrive in, and saves reversing them afterwards. sbfsFind splits into a walk and a check. "cd /" and "cd .." both end at the root quite legitimately, and had no way to say so through a routine whose only word for the root was "missing". Typing a program's name now tries two places in order: where you are, then /Apps. The first makes a program you are working on the one that runs; the second lets Snake work from anywhere. A word already beginning with a separator has said where to look, so only that place is tried. osChangeDir exists so that "a program may move about, and the shell puts the working directory back" is a thing that can happen rather than a promise about nothing. Both halves of that were unfalsifiable without it: with no way for a program to move, removing the restore changed no test. Wander is the program that moves - it goes where it is told and reads a file there by a bare name - and with it on the disk, removing the restore fails. The remembered file is dropped whenever what a relative path means changes: a cd, a program calling osChangeDir, a program exiting. Removing all of them fails the test and removing any one of them does not, because today every path into that cache belongs to a program that exits. It is kept in all three because the cost is a call and the failure is a file's blocks being handed out under another file's name. The cwd fixture holds two files called notes.txt saying different things, and a Say.sbx in /A that is really hello. Two copies of one program, or two copies of one file, would have passed with the whole of this deleted. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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588e02aff5 |
Double CosmOS's half of the machine, and check that it fits
The memory map gave CosmOS 0x0000 through 0x1FFF of Program Memory and applications 0x2000 and above. CosmOS is 8141 bytes at the previous commit, which is fifty one bytes short of the line, and the next thing added to it went over. GOING OVER DOES NOT FAIL WHERE IT HAPPENS. Nothing enforces the division: an application says where it goes with #Base and the loader puts it there, so a CosmOS that has grown past 0x1FFF simply has the next program loaded written over the end of it. What breaks is whichever part of the shell that program happened to cover, at whatever later moment somebody uses it. It turned up here as the monitor's assemble command answering "I do not know" to valid instructions, several commands into a session, on a machine that had booted perfectly well. Both halves are doubled: applications now start at 0x4000 in Program Memory and 0x2000 in Data Memory. That is 16K of code and 8K of data for the system, against the 8775 and 2948 it uses today. Both were on the same trajectory, and moving them together means the twenty files that say #Base are edited once rather than twice. The standalone loader's loadable.asm keeps its old base: it belongs to the loader CosmOS grew out of, not to CosmOS, and its addresses answer to a different program. The unbased-segment diagnostic keeps its old base too - it exists to produce an error message that names the address, and the message is what is recorded. Tests/docs.sh now reads the two limits out of the table in the README and measures both segments against them. It reads them rather than being told them because the table is the specification, and this is the second time in this project that the thing nobody checked is the thing that rotted. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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D2: the machine walks a path
sbfsFind takes a path where it used to take a name: names with '/' between them, walked from the root, with '.' and '..'. Each name is looked for among the entries whose parent is where the walk has got to. A bare name is a path of one name, so everything written before directories existed still works and still costs one walk of the directory. sbfsMount takes either version. On a version one disk every entry has zeroes where a parent goes and the walk starts at zero, so the comparison always agrees - which is how a flat disk reads correctly here with nothing done to it. PROGRAMS DID NOT HAVE TO BE TAUGHT ANY OF THIS. Resolution sits inside sbfsFind, below the services, so every osFile call keeps its signature and a path is simply a longer name. Type, More, Edit and the assembler gained subdirectories without a line changing in any of them. Four things this turned up, none of which was the path walk: load copied the path into a buffer sized for a NAME, so anything over 22 characters was cut short - and cut short into a path that often still resolved. "/Apps/Deep/../../Apps/Say.sbx" became "/Apps/Deep/../../Apps/" and reported that the program was a directory. That is the whole of what looked like a bug in '..', and it cost most of the time here. load on a directory SUCCEEDED. A directory has no blocks, so reading it reads nothing and leaves the staging area holding whatever was staged last - which, if that was a program, still says SBEX and still has a working entry address. It handed back the program before it. Refused outright now. delete and rename on a directory are refused, and save refuses one up front rather than failing at the rename and leaving a temporary behind. Deleting a directory frees an entry index, and a parent IS an index, so the next file created would take it and inherit the children. create writes the parent rather than leaving it zero by luck. It would be zero - delete wipes all thirty two bytes and a fresh entry never had any - but that is a fact about two other routines, and a file appearing inside a directory it was never put in is not a failure anybody would think to look for. dir marks directories and counts them apart from files, because at this point it was calling them files of no bytes. Two hazards written down in the design note turned out not to be real, and both were checked rather than argued about: The lookup cache holding 22 bytes of a longer path cannot hand back the wrong file - textSame wants both strings to end in the same place, so a cut down entry misses. It can never HIT either, though, so every path longer than a name went to the disk every time; it holds a whole path now. The allocator stepping over directories changes nothing any test can see. A directory has no start as well as no blocks, so its bounds are nought to nought and no candidate begins before it ends. The four instructions stay, with a comment saying they are not load bearing today and why they are there anyway. makedisks.sh resolves its build path before it cds. Given a relative one it carried on and quietly built disks missing some of their files, which is how the tree fixture lost a file and sent me looking for a bug in '..'. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |