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Added some comments that explain some '???' moments

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CPunch 2021-12-08 16:35:04 -06:00
parent efb4ef5035
commit 3eecd3a8b0
1 changed files with 8 additions and 6 deletions
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14
luac.py
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@ -210,16 +210,17 @@ class LuaUndump:
template = instr_lookup_tbl[opcode]
instruction = Instruction(template.type, template.name)
# i read the lopcodes.h file to get these bit position and sizes.
instruction.opcode = opcode
instruction.A = _get_bits(data, 6, 8)
instruction.A = _get_bits(data, 6, 8) # starts after POS_OP + SIZE_OP (6), with a size of 8
if instruction.type == InstructionType.ABC:
instruction.B = _get_bits(data, 23, 9)
instruction.C = _get_bits(data, 14, 9)
instruction.B = _get_bits(data, 23, 9) # starts after POS_C + SIZE_C (23), with a size of 9
instruction.C = _get_bits(data, 14, 9) # starts after POS_A + SIZE_A (14), with a size of 9
elif instruction.type == InstructionType.ABx:
instruction.B = _get_bits(data, 14, 18)
instruction.B = _get_bits(data, 14, 18) # starts after POS_A + SIZE_A (14), with a size of 18
elif instruction.type == InstructionType.AsBx:
instruction.B = _get_bits(data, 14, 18) - 131071
instruction.B = _get_bits(data, 14, 18) - 131071 # Bx is now signed, so just sub half of the MAX_UINT for 18 bits
chunk.appendInstruction(instruction)
@ -247,7 +248,8 @@ class LuaUndump:
for i in range(num):
chunk.appendProto(self.decode_chunk())
# debug stuff
# debug stuff, maybe i'll add this to chunks to have better disassembly annotation in the future?
# eh, for now just consume the bytes.
# line numbers
num = self.get_int()