ScriptOp.fromAsm constructor

ScriptOp.fromAsm(String asm)

Interpret a single script ASM string into a ScriptOp.

Implementation

factory ScriptOp.fromAsm(String asm) {

  if (asm.isEmpty) throw InvalidScriptAsm();

  // If it starts with OP_, then it is an opcode
  if (asm.startsWith("OP_")) {

    final code = scriptOpNameToCode[asm.substring(3)];
    if (code == null) throw InvalidScriptAsm();

    // Do not allow push data opcodes
    if (code >= pushData1 && code <= pushData4) throw InvalidScriptAsm();

    return ScriptOpCode(code);

  }

  // If "-1" or "81", then it is a 1NEGATE op code
  if (asm == "-1" || asm == "81") return ScriptOpCode(op1Negate);

  // If "80" then it is zero
  if (asm == "80") return ScriptOpCode(0);

  // If it is in the form of <n-bytes>, then it represents a push data matcher
  // of n bytes
  final nBytesStr = pushdataMatcherRegExp.firstMatch(asm)?.group(1);
  if (nBytesStr != null) {
    final n = int.tryParse(nBytesStr);
    if (n == null || n == 0 || n > 0xffffffff) throw InvalidScriptAsm();
    return ScriptPushDataMatcher(n);
  }

  // Otherwise assume hex. Provide opcode if available or else pushdata

  late Uint8List bytes;
  try {
    bytes = hexToBytes(asm);
  } on FormatException {
    throw InvalidScriptAsm();
  }

  return bytes.length == 1 ? ScriptOp.fromNumber(bytes[0]) : ScriptPushData(bytes);

}