AnachronautandClaude Opus 5
588e02aff5
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
177 lines
3.7 KiB
NASM
177 lines
3.7 KiB
NASM
; A program that keeps a file without knowing how a filesystem works.
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;
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; INCLUDES NOTHING BUT THE SERVICE NAMES. No sbfs.asm, no console.asm - the system has both
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; of those running already, and this asks it rather than carrying a second copy. That is the
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; whole point of the program: if it works, a tool that edits documents does not need two and
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; a half kilobytes of filesystem bound into it.
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;
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; It writes a file, reads it back, says how big it was, renames it, and takes it away again,
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; which is every file service there is.
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;
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; ---- What you will see before the handlers are written ----
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;
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; The numbers are pinned but nothing answers to them yet, so the first call dispatches
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; through an empty vector and the machine stops:
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;
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; Fault: Software vector 21, dispatched from Program Address 0x200B, has no handler
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; installed.
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;
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; That is the fault working properly rather than the program being broken. A vector with
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; nothing in it is not a jump to address zero; it is a stop, with the vector named and the
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; place it was called from named, which is as much as the machine can know.
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#Include services.asm
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#Program
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#Base 0x4000
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start:
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; ---- Write it ----
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;
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; A and B together are how many bytes there are, most significant first, which is the
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; same sixteen bits a length always is on this machine.
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SETD.0 Name
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SETD.1 Body
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RSTA
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INIB 0d22 ; The text and its newline. NOT the zero the assembler put
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SWI osFileSave ; after it: a text file ends where the text ends.
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BNQ noSave
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SETD.0 SavedText
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SWI osPrintString
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; ---- Read it back ----
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;
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; DP3 comes back holding how many bytes there were, because that is one of the two things
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; a service is allowed to answer in and a file that fits in memory has a length that fits
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; in a pointer.
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SETD.0 Name
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SETD.1 Landing
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SWI osFileRead
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BNQ noRead
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SETD.0 ReadText
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SWI osPrintString
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PSHD.3
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POPB ; The low byte is on top, the way a pointer is pushed.
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POPA
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SWI osPrintNumber
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SETD.0 BytesText
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SWI osPrintString
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; And now the length is needed for something rather than just reported. What came back is
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; a file, not a string: nothing on the disk ends in a zero byte, because the entry says
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; where it stops instead. So a zero goes on the end before it can be printed as one.
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SETD.1 Landing
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PSHD.3
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POPB
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POPA
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walkToEnd:
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BRB atEnd
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INCD.1
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DECB
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BRI walkToEnd
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atEnd:
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RSTA
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STA.1
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SETD.0 Landing
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SWI osPrintString
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; ---- Call it something else ----
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SETD.0 Name
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SETD.1 OtherName
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SWI osFileRename
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BNQ noRename
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SETD.0 RenamedText
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SWI osPrintString
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; ---- And take it away ----
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SETD.0 OtherName
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SWI osFileDelete
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BNQ noDelete
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SETD.0 DeletedText
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SWI osPrintString
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; Reading it now should fail, and a service saying no is not the same as one that is not
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; there: this comes back with an answer rather than stopping the machine.
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SETD.0 OtherName
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SETD.1 Landing
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SWI osFileRead
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BRQ stillThere
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SETD.0 GoneText
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SWI osPrintString
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SWI osExit
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stillThere:
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SETD.0 StillText
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SWI osPrintString
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SWI osExit
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noSave:
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SETD.0 NoSaveText
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SWI osPrintString
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SWI osExit
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noRead:
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SETD.0 NoReadText
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SWI osPrintString
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SWI osExit
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noRename:
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SETD.0 NoRenameText
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SWI osPrintString
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SWI osExit
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noDelete:
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SETD.0 NoDeleteText
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SWI osPrintString
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SWI osExit
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#Data
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#Base 0x2000
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Name:
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"kept.txt"
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OtherName:
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"moved.txt"
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Body:
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"a file kept by asking
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"
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SavedText:
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"saved it
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"
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ReadText:
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"read it back, "
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BytesText:
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" bytes:
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"
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RenamedText:
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"renamed it
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"
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DeletedText:
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"deleted it
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"
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GoneText:
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"and it is gone
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"
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StillText:
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"but it is still there
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"
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NoSaveText:
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"it would not save
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"
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NoReadText:
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"it would not read
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"
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NoRenameText:
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"it would not rename
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"
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NoDeleteText:
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"it would not delete
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"
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Landing:
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#Reserve 0d256
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