emitCopy function

List<int?> emitCopy(List<int?> opcodes, Uint8List source, int offset, int len,)

Implementation

List<int?> emitCopy(List<int?> opcodes, Uint8List source, int offset, int len) {
  int code, codeIdx;

  opcodes.add(null);
  codeIdx = opcodes.length - 1;
  code = 0x80; // set the MSB

  // offset and length are written using a compact encoding
  // where the state of 7 lower bits specify the meaning of
  // the bytes that follow
  if (offset & 0xff > 0) {
    opcodes.add(offset & 0xff);
    code |= 0x01;
  }

  if (offset & 0xff00 > 0) {
    opcodes.add(_zeroFillRightShift((offset & 0xff00), 8));
    code |= 0x02;
  }

  if (offset & 0xff0000 > 0) {
    opcodes.add(_zeroFillRightShift((offset & 0xff0000), 16));
    code |= 0x04;
  }

  if (offset & 0xff000000 > 0) {
    opcodes.add(_zeroFillRightShift((offset & 0xff000000), 24));
    code |= 0x08;
  }

  if (len & 0xff > 0) {
    opcodes.add(len & 0xff);
    code |= 0x10;
  }

  if (len & 0xff00 > 0) {
    opcodes.add(_zeroFillRightShift((len & 0xff00), 8));
    code |= 0x20;
  }

  if (len & 0xff0000 > 0) {
    opcodes.add(_zeroFillRightShift((len & 0xff0000), 16));
    code |= 0x40;
  }

  // place the code at its position
  opcodes[codeIdx] = code;

  return opcodes;
}