readFromBufferAsSigned function

int readFromBufferAsSigned(Pointer<Uint8> buffer, int offset, int byteCnt)

Read a specified piece of the buffer and convert it to an integer number (signed).

If offset is aligned, tat is if (offset mod byteCnt) = 0, the function is more efficient. On unaligned data, byte-by-byte copying takes place. The only valid values for byteCnt 1, 2, 4 and 8 (any other will cause a MemException).

Implementation

int readFromBufferAsSigned(Pointer<Uint8> buffer, int offset, int byteCnt) {
  if (offset % byteCnt == 0) {
    // the offset is aligned
    switch (byteCnt) {
      case 1:
        return Pointer<Int8>.fromAddress(
          buffer.address + offset,
        ).asTypedList(1)[0];
      case 2:
        return Pointer<Int16>.fromAddress(
          buffer.address + offset,
        ).asTypedList(1)[0];
      case 4:
        return Pointer<Int32>.fromAddress(
          buffer.address + offset,
        ).asTypedList(1)[0];
      case 8:
        return Pointer<Int64>.fromAddress(
          buffer.address + offset,
        ).asTypedList(1)[0];
      default:
        throw MemException(
          "Invalid byte count for reading int from buffer: $byteCnt",
        );
    }
  } else {
    // the offset not aligned - copying byte by byte
    final bytes = Uint8List(byteCnt);
    for (var i = 0; i < byteCnt; i++) {
      bytes[i] = buffer[offset + i];
    }
    return fromBytesAsSigned(bytes);
  }
}