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Implement extended opcode decoder for V5+

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The 0xBE prefix byte triggers extended opcode parsing. Reads the
opcode number from the next byte, then parses operand types using
the same format as VAR opcodes. Required for all V5+ games.
This commit is contained in:
Jared Miller 2026-02-10 13:37:27 -05:00
parent 11d939a70f
commit e61dcc3ac4
Signed by: shmup
GPG key ID: 22B5C6D66A38B06C
1 changed files with 11 additions and 2 deletions
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13
src/mudlib/zmachine/zopdecoder.py
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@ -70,7 +70,7 @@ class ZOpDecoder:
log(f"Decode opcode {opcode:x}") log(f"Decode opcode {opcode:x}")
# Determine the opcode type, and hand off further parsing. # Determine the opcode type, and hand off further parsing.
if self._memory.version == 5 and opcode == 0xBE: if self._memory.version >= 5 and opcode == 0xBE:
# Extended opcode # Extended opcode
return self._parse_opcode_extended() return self._parse_opcode_extended()
@ -134,7 +134,16 @@ class ZOpDecoder:
def _parse_opcode_extended(self): def _parse_opcode_extended(self):
"""Parse an extended opcode (v5+ feature).""" """Parse an extended opcode (v5+ feature)."""
raise NotImplementedError("Extended opcodes (v5+) not yet implemented") log("Opcode is extended")
# Read the extended opcode number
opcode_num = self._get_pc()
log(f"Extended opcode number: {opcode_num:x}")
# Parse the operand types byte and retrieve operands
operands = self._parse_operands_byte()
return (OPCODE_EXT, opcode_num, operands)
def _parse_operand(self, operand_type): def _parse_operand(self, operand_type):
"""Read and return an operand of the given type. """Read and return an operand of the given type.