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Ability to relocate song address table #320

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a0c8d27
Search for footer and use pointer there
Supremekirb Mar 11, 2025
c12632b
Small fix to error
Supremekirb Mar 11, 2025
66fe4e8
Use SPC address in error reporting
Supremekirb Mar 12, 2025
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37 changes: 36 additions & 1 deletion coilsnake/model/eb/musicpack.py
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Original file line number Diff line number Diff line change
Expand Up @@ -805,7 +805,15 @@ def load_from_files(self, file_loader):
raise CoilSnakeInternalError("Dependent song is not in same pack as parent song")

class EngineMusicPack(SongMusicPack):
# This is used in modified engine.bins to have a different pointer to the song table.
# asar assembler uses UTF-8 encoding.
# The footer can be located anywhere, though, but the convention is at the end.
# The format is this string followed by a pointer to the song table.
FOOTER_IDENTIFIER_BYTES = bytes("COILSNAKE SONG TABLE POINTER", encoding="UTF-8")

# Default song table address. Used when the footer is not found.
SONG_ADDRESS_TABLE_ADDR = 0x2E4A

ENGINE_FIXED_PARTS = {0x6E00: 'data-6E00.bin', 0x6F80: 'data-6F80.bin', 0x0500: 'engine.bin'}
# These values are for the part starting at $0500, containing the main SPC program
MAIN_PART_ADDR = 0x0500
Expand Down Expand Up @@ -940,9 +948,36 @@ def get_song_address_table_data(self, size: int) -> Block:
start_addr = EngineMusicPack.SONG_ADDRESS_TABLE_ADDR - EngineMusicPack.MAIN_PART_ADDR
return block[start_addr:start_addr + size]

def get_song_address_table_pointer(self) -> int:
# search for CoilSnake footer
# (there's probably a better way to do this. I don't know how to best work with Block objects.)
engine_bytes = bytes(self.engine_parts[EngineMusicPack.MAIN_PART_ADDR].to_list())
footer_match = EngineMusicPack.FOOTER_IDENTIFIER_BYTES
song_table_pointer_pointers: list[int] = []
try:
song_table_pointer_pointers = [(i+len(footer_match)) for i in range(len(engine_bytes)) if engine_bytes[i:i+len(footer_match)] == footer_match]
except OutOfBoundsError:
pass
if len(song_table_pointer_pointers) > 1:
raise InvalidUserDataError("engine.bin contains more than one footer pointing to the location of the song table. Found footers at: {} (SPC addresses)".format(
["$" + hex(i-len(footer_match) + 0x500)[2:].zfill(4).upper() for i in song_table_pointer_pointers]
))

if len(song_table_pointer_pointers) == 0:
log.info("Using default song table location.")
target_addr = EngineMusicPack.SONG_ADDRESS_TABLE_ADDR
else:
target_addr = engine_bytes[song_table_pointer_pointers[0]:song_table_pointer_pointers[0]+2]
target_addr = int.from_bytes(target_addr, 'little')
log.info("Relocating song table to {} based on footer found in the engine.".format(
hex(target_addr).zfill(4)
))

return target_addr

def set_song_address_table_data(self, block: Block) -> None:
assert self.parts
self.set_aram_region(EngineMusicPack.SONG_ADDRESS_TABLE_ADDR, block.size, block)
self.set_aram_region(self.get_song_address_table_pointer(), block.size, block)

@classmethod
def apply_engine_patches(cls, engine_block: Block) -> Block:
Expand Down