AnachronautandClaude Opus 5
4fd8bf7b3f
DPUP takes an immediate, so an offset of one is legal and does exactly the right thing. It is also three bytes where INCD is two, and reads as "offset the pointer up by one" where INCD reads as "step the pointer". 56 of them across 15 files: the system, the assembler, the editor, and eight test programs. CosmOS is 9,564 bytes to 9,537, the native assembler 11,648 to 11,635, and every program in the repository together 49 bytes lighter. The worst offender was numbers.asm, written this week, where every sixteen bit helper reaches the low byte and comes back the long way round. It is the file every other part of the assembler includes, so it is the first thing anybody reads when they go looking - and it was teaching them the long way. Pattern matched off sbfs.asm rather than off the instruction table I had just embedded in two programs. THIS IS NOT TWO WAYS TO DO ONE THING. DPUP takes an arbitrary number, so one is inevitably among them; INCD earns its place by making the common case a byte cheaper. The overlap is structural and the choice is a usage question, which is a linter's job rather than an ISA's - "DPUP.n 0d01: INCD.n does this in a byte less" is a mechanical rule with no judgement in it. Nothing needed re-recording, which was not a foregone conclusion: cosmosBreak prints the system addresses the registers happened to hold, and they did not move. Both assemblers still produce identical bytes and CosmOS still builds itself to a fixed point. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW
157 lines
3.0 KiB
NASM
157 lines
3.0 KiB
NASM
; Reading the SplitBit Filesystem.
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;
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; The disk this reads was made by SplitDisk, which is the other implementation of the same
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; format. That is what makes this worth running: the library is being checked against
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; something written by different code working from the same written specification, rather
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; than against itself. If the two ever drift, this is where it shows.
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;
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; The cases here are the ones most likely to be wrong. across.txt is longer than a block,
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; so reading it has to carry on from one to the next. Its entry, and the two after it, are
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; in the second directory block, so finding it has to walk past the end of the first.
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; aName22CharactersLong! fills the name field exactly, so there is no zero on the end of
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; it to stop a comparison. empty.txt has no blocks at all.
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;
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; Correct output is:
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; greeting.txt 0000 11 hello from a file
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; across.txt 0002 BC ABCDEFGH...
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; aName22CharactersLong! 0000 16 exactly twenty two!!!!
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; empty.txt 0000 00
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; absent.txt missing
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#Include print.asm
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#Include sbfs.asm
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#Program
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start:
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CALL sbfsMount
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BRQ mounted
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SETD.0 NoMount
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CALL printString
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CALL lineFeed
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HALT
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mounted:
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SETD.0 WantGreeting
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CALL showFile
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SETD.0 WantAcross
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CALL showFile
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SETD.0 WantLongName
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CALL showFile
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SETD.0 WantEmpty
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CALL showFile
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SETD.0 WantAbsent
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CALL showFile
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HALT
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; DP0 names a file. Prints its name, what the directory says about it, and then the file
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; itself. DP3 keeps the name across the calls, because it is the pointer a CALL does not
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; put back.
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showFile:
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PSHD.0
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POPD.3
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CALL printString
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CALL blankSpace
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PSHD.3
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POPD.0
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CALL sbfsFind
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BRQ showFound
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SETD.0 Missing
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CALL printString
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CALL lineFeed
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RET
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showFound:
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SETD.0 SbfsFileBlocks
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LDA.0
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CALL printByteHex
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INCD.0
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LDA.0
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CALL printByteHex
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CALL blankSpace
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SETD.0 SbfsFileTail
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LDA.0
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CALL printByteHex
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CALL blankSpace
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SETD.1 Landing
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CALL sbfsRead
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BRQ showContents
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SETD.0 Failed
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CALL printString
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CALL lineFeed
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RET
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; Writes out exactly as many bytes as the file has, and no more. The length is the block
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; count and the tail side by side: blocks times 256 plus the tail is the same as putting
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; the count in the high byte and the tail in the low one.
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showContents:
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SETD.0 Landing
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SETD.1 SbfsFileBlocks
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INCD.1
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LDA.1
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SETD.1 LeftHigh
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STA.1
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SETD.1 SbfsFileTail
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LDA.1
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SETD.1 LeftLow
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STA.1
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showLoop:
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SETD.1 LeftHigh
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LDA.1
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SETD.2 LeftLow
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LDB.2
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OR
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BRQ showEnd ; Nothing left of it.
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LDA.0
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OUTA 0x00
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INCD.0
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SETD.1 LeftLow
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LDA.1
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DECA
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STA.1
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BRC showBorrow ; It went under, so the high byte owes one.
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BRI showLoop
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showBorrow:
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SETD.1 LeftHigh
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LDA.1
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DECA
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STA.1
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BRI showLoop
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showEnd:
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CALL lineFeed
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RET
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#Data
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WantGreeting:
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"greeting.txt"
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WantAcross:
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"across.txt"
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WantLongName:
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"aName22CharactersLong!"
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WantEmpty:
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"empty.txt"
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WantAbsent:
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"absent.txt"
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NoMount:
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"no mount"
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Missing:
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"missing"
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Failed:
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"failed"
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LeftHigh:
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0x00
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LeftLow:
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0x00
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Landing:
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#Reserve 0d1024
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