AnachronautandClaude Opus 5
3449405b18
CosmOS had 1,161 bytes of Program Memory left before the address applications load at, and Tab completion is not going to fit in that with anything to spare. So the wall moves up one page: the system keeps below 0x4FFF and 0x2FFF, and an application is based at 0x5000 and 0x3000. A PAGE IS A CHEAP THING TO GIVE IT AND AN EXPENSIVE THING TO RUN OUT OF. An application still has 44K of Program Memory before the vector table and the largest one here uses 7.5K, so what was taken from applications is space nothing has ever asked for - while what the system gained is the difference between building the next thing and counting bytes while building it. Not doubling, which was the version that would have cost application space worth minding. One page, and the same again when it is needed. Nothing in the machine knows where the wall is, so this is 34 #Base lines, one threshold in the fault handler, and the table in the CosmOS README that Tests/docs.sh reads its limits out of. The native assembler's scratch map had to move with it, and docs.sh said so before anything ran: its data reached 0x40D6 and its buffers began at 0x4000, so they were sitting on its variables. That file already carries a paragraph about the floor coming up and the map staying where it was. It has happened twice now, and been caught by a check the first time wrote. Twenty three recordings are the same runs a page higher. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW
246 lines
3.9 KiB
NASM
246 lines
3.9 KiB
NASM
; Writes a file one block at a time, without ever holding the whole of it.
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;
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; This is the write side of what Stream demonstrates for reading: a file bigger than the
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; memory building it. It writes as many blocks as it is asked for, each one filled with a
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; pattern that says which block it is, so that what comes off the disk afterwards can be
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; checked against what should have gone on rather than merely being the right length.
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;
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; The argument is how many blocks, in decimal. The last one is deliberately a part block,
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; because a tail is the case every off-by-one in a filesystem hides in.
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;
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; Written by Anachronaut
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#Include services.asm
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#Program
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#Base 0x5000
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start:
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SETD.0 Argument
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INIB 0d8
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SWI osArgument
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SETD.0 Argument
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LDA.0
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BRA useDefault
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CALL readCount
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BRI counted
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useDefault:
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INIA 0d4
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SETD.0 Blocks
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STA.0
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counted:
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; Nothing may be zero blocks: the tail below would then be the whole file.
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SETD.0 Blocks
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LDA.0
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BNA haveCount
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INIA 0d1
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STA.0
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haveCount:
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; Whole blocks, and a tail of forty bytes on the end of them.
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SETD.0 Name
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SETD.3 0x00 0x00
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SETD.0 Blocks
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LDA.0
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PSHA
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POPB
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RSTA
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PSHA
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PSHB
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POPD.3
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SETD.0 Name
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INIA 0d40
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SWI osFileStart
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BNQ startFailed
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; Each whole block, filled with its own number.
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RSTA
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SETD.0 Which
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STA.0
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nextBlock:
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SETD.0 Which
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LDA.0
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SETD.2 Blocks
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LDB.2
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CCF
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SUB
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BRQ theTail
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CALL fillBlock
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SETD.1 Block
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SETD.0 Which
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LDA.0
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RSTB
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PSHA
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POPB
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RSTA
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SWI osFileWrite
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BNQ writeFailed
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SETD.0 Which
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LDA.0
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INCA
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STA.0
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BRI nextBlock
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theTail:
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; And the part block at the end, which is the same fill cut short by the size given at
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; the start. Only the first forty bytes of it will belong to the file.
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CALL fillBlock
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SETD.1 Block
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SETD.0 Which
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LDA.0
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RSTB
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PSHA
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POPB
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RSTA
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SWI osFileWrite
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BNQ writeFailed
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; And how big it turned out to be, which here is what was asked for: this one knows its
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; size from the start. Something that did not - an assembler, say - would ask for more
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; than it needed and say the truth here.
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RSTA
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PSHA
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SETD.0 Blocks
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LDA.0
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PSHA
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POPD.3
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INIA 0d40
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SWI osFileDone
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BNQ doneFailed
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SETD.0 Wrote
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SWI osPrintString
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SETD.0 Blocks
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LDB.0
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RSTA ; A and B together are the number, so the count is the low half.
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SWI osPrintNumber
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SETD.0 AndTail
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SWI osPrintString
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RSTA
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SWI osExit
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; The block becomes 256 copies of the block number plus a fixed byte, so that a block
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; written into the wrong place is visible rather than merely being bytes.
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fillBlock:
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SETD.0 Block
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SETD.1 Which
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LDA.1
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INIB 0x41
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CCF
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ADD
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MVQA
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RSTB
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fillLoop:
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STA.0
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INCD.0
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DECB
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BNB fillLoop
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RET
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; The argument, in decimal, into Blocks. Anything that is not a digit ends it.
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readCount:
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RSTA
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SETD.1 Blocks
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STA.1
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SETD.0 Argument
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countLoop:
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LDA.0
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BRA countDone
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INIB 0x30
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CCF
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SUB
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MVQA
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INIB 0d10
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CCF
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SUB
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BNC countDone ; Not a digit, so the number ended.
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SETD.1 Blocks
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LDB.1
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PSHA
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INIA 0d10
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CALL timesTen
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POPA
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SETD.1 Scratch
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LDB.1
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CCF
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ADD
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MVQA
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SETD.1 Blocks
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STA.1
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INCD.0
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BRI countLoop
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countDone:
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RET
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; B times ten into Scratch, by adding it up. Nothing here is bigger than a byte.
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timesTen:
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RSTA
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SETD.0 Scratch
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STA.0
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INIA 0d10
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tenLoop:
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PSHA
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SETD.0 Scratch
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LDA.0
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SETD.2 TenHold
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STB.2
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LDB.2
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CCF
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ADD
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MVQA
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STA.0
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POPA
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DECA
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BNA tenLoop
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RET
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startFailed:
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SETD.0 NoStart
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SWI osPrintString
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INIA 0d1
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SWI osExit
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writeFailed:
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SETD.0 NoWrite
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SWI osPrintString
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INIA 0d1
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SWI osExit
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doneFailed:
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SETD.0 NoDone
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SWI osPrintString
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INIA 0d1
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SWI osExit
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#Data
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#Base 0x3000
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Name:
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"poured.dat"
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Argument:
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#Reserve 0d9
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Blocks:
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0x00
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Which:
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0x00
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Scratch:
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0x00
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TenHold:
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0x00
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Block:
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#Reserve 0d256
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Wrote:
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"poured "
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AndTail:
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" blocks and a tail of 40
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"
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NoStart:
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"could not start it
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"
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NoWrite:
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"could not write a block
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"
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NoDone:
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"could not finish it
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"
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