grpcEncodeFrameWithFlags function

List<int> grpcEncodeFrameWithFlags(List<int> messageBytes, int flags)

Encode a frame with an explicit flags byte (1 flag + 4-byte big-endian length + message bytes).

This is the flag-byte-aware sibling of grpcEncodeFrame: instead of the single compressed bool it takes the full flag bitset, so a Connect streaming end-of-stream envelope can set grpcFlagEndOfStream (bit 1). Build flags with grpcMakeFlags. grpcEncodeFrame(bytes, compressed: c) is exactly grpcEncodeFrameWithFlags(bytes, c ? grpcFlagCompressed : 0).

Implementation

List<int> grpcEncodeFrameWithFlags(List<int> messageBytes, int flags) {
  var length = messageBytes.length;
  var frame = List<int>.filled(_headerSize + length, 0);
  // Byte 0: the full flag bitset (compression bit 0, end-of-stream bit 1).
  frame[0] = flags & 0xFF;
  // Bytes 1-4: message length, big-endian.
  frame[1] = (length >>> 24) & 0xFF;
  frame[2] = (length >>> 16) & 0xFF;
  frame[3] = (length >>> 8) & 0xFF;
  frame[4] = length & 0xFF;
  // Bytes 5+: message payload.
  for (var i = 0; i < length; i++) {
    frame[_headerSize + i] = messageBytes[i];
  }
  return frame;
}