bfc46d982e72aa21f6bf0b367872230b624f9875
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Commits
| Author | SHA1 | Message | Date | |
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  AnachronautandClaude Opus 5
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bfc46d982e |
Play reads a tune from a file
The loader, and the reason it is small: everything in a tune is an offset from wherever it was put, so taking one means adding the base to two tables and pointing four voices at their order lists. No sequence is walked. Nothing inside one is an address to be found and corrected, which is the difference between a malformed tune that plays wrongly and one that takes the loader with it. "SBTU", version, the tick in cycles, how many patches and sequences, offsets to the two tables, an order list each, and the patch each voice starts on. The magic is checked before anything else, because from there on the loader follows what the offsets name. break.sh shows what that guard is worth: without it, handing Play a PROGRAM runs the machine away until the cycle limit, rather than saying it is not a tune. PatchTable, SequenceTable and VoiceStart became pointers, so the engine does not care whether a tune came out of a file or was assembled in. Play's built-in tune now hands over the same three addresses a loaded one would, in eight lines - which is what keeps the two paths from drifting, and what made this rung change no scheduler code at all. Tests/maketune.py lays the fixture out byte by byte. IT IS NOT THE COMPILER: the sequences and the patches are literal bytes and the only thing computed is where each piece lands. That is the point - the loader is checked by something that does not share its idea of the format, which is the same reason SplitDisk and sbfs.asm share nothing but a specification. Both notes in the fixture are number 60, so the octave between them is a 0x80 command loading the second patch out of the file: the header, the tick, the relocation, an order list and a patch from a file, measured in one go. Play and the tune live on quiet.img rather than cosmos.img, so a fixture does not move ten recordings every time it changes size. 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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5d9b39514b |
The player speaks indices, which is the shape a file has to be
Order lists hold one-byte sequence indices and 0x80 holds a one-byte patch index. Two tables, PatchTable and SequenceTable, are the only places an address lives. THAT IS WHAT MAKES A TUNE LOADABLE WITHOUT WALKING IT. Nothing inside a sequence or an order list is an address, so putting one in memory means adding the load address to two arrays and nothing else. The alternative is a loader that parses every sequence looking for addresses to correct, which is a loader a malformed file can walk off a cliff. Doing it now, while the tune is still assembled in, means the file form and the assembled form are the same shape - so reading a tune from a file will change no engine code at all. The whole point of the rung. The patch each voice starts on moved from four calls in a row into VoiceStart, four declared bytes, and loadStartPatches reads them. A starting instrument is state and belongs where state goes: the user's ruling is that a voice with undefined state is an error, prompted by noticing that a program run a second time starts with the memory the first run left, because loading is what initialises and running is not. Order lists also halved in size, which was not the reason but is welcome. Hand-writing the two tables is exactly the tedium the compiler exists to remove - every sequence counted into its place, and moving one means renumbering. Better to feel that here than after a tool has baked the shape in. Verified by rendering: bar for bar the same piece. break.sh confirms the scaling, since an index is doubled to reach a two-byte entry and halving that step lands on the wrong sequence and fails four checks. 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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8029063bdc |
Sequences, order lists, and a command that changes the instrument
The rung between M3 and M4, and the point of doing it before the format: the engine learns the tracker's model with the tune still assembled in, so M4 becomes serialising a thing that exists rather than designing a thing that does not. A voice no longer walks one long track. 0xFF now means THIS SEQUENCE ended, and the voice takes the next address from an order list of its own. That is where repetition comes from, and it costs no notation: the bass plays the same sequence in the first bar and the last and it is written once. Per voice rather than one shared table of four-column rows, because a voice's order cursor is then a pointer it advances by itself - the same LDD and STD move everything else here makes. Four columns is how it reads, not how it is stored. Sequences also carry COMMANDS, which take no tick: the reader acts and reads the next event on the same boundary. One is defined, 0x80, which plays the rest of that voice on another patch, and the other 125 values are left alone. A patch change reshapes whatever is still ringing on the voice and nothing can be done about that - a channel has one set of parameters and a note in its release is using them - so it is a fact about the hardware and the cure is a rest, which is the composer's. The engine moved to Libraries/player.asm rather than being copied into the test a second time, now that it is big enough to drift. Play supplies the tune and the beat; the library supplies the scheduler, the patch loader and a voice's state. Verified by rendering: bar for bar identical across the move. AND THE TEST FOUND A REAL FLAW IN THE FORMAT, which is the whole argument for building the reader first. The order list ended with 0x0000, on the reasoning that no sequence could live below the 0x3000 this program is based at. True of a loaded program, false of a boot image whose data starts at zero - so the first test written against it read its own first sequence as the end of the list and played nothing at all. It is 0xFFFF now, which mirrors the 0xFF ending a sequence and is impossible everywhere: a sequence at 0xFF00 or above has fewer bytes left than it needs. An address is a poor place to hide a flag unless the address is impossible in every program, not just this one. One order list in the test now really ends, because otherwise nothing reached the terminator at all: every voice sat on a long rest and the break went unnoticed. With it, breaking the test reads garbage past the end and the counter sums two notes at 781 hertz. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |