encodeRowInto static method

int encodeRowInto(Uint8List row, Uint8List output, int start)

Encodes row into output at start and returns the next write offset.

output must have at least maxEncodedLength bytes available beyond start. Writing into a caller-owned buffer lets a whole image be encoded without allocating per row or per run, which dominates the cost of compressing large planes.

Implementation

static int encodeRowInto(Uint8List row, Uint8List output, int start) {
  int write = start;
  int offset = 0;
  while (offset < row.length) {
    int runLength = _repeatedRunLength(row, offset);
    if (runLength >= 3) {
      output[write++] = 257 - runLength;
      output[write++] = row[offset];
      offset += runLength;
      continue;
    }

    final int literalStart = offset;
    offset += runLength;
    while (offset < row.length && offset - literalStart < 128) {
      runLength = _repeatedRunLength(row, offset);
      if (runLength >= 3) {
        break;
      }
      final int remaining = 128 - (offset - literalStart);
      offset += runLength.clamp(1, remaining);
    }
    final int literalLength = offset - literalStart;
    output[write++] = literalLength - 1;
    output.setRange(write, write + literalLength, row, literalStart);
    write += literalLength;
  }
  return write;
}