// a deflater that writes out buffered data on flush()
// (and also flushes the underlying stream)
// You can use this for highly compressed piece-wise streams
// such as logs or websockets where each piece is compressed
// using the dictionaries of earlier pieces.
// For client-side try: https://github.com/dasmoth/jszlib
static DeflaterOutputStream deflaterOutputStream_syncFlush(File f) ctex {
  ret new DeflaterOutputStream(newFileOutputStream(f), true);
}

static DeflaterOutputStream deflaterOutputStream_syncFlush(OutputStream out) ctex {
  ret new DeflaterOutputStream(out, true);
}

Began life as a copy of #1031078