[undertow-dev] transferFrom writes more than requested

With the code below, the expected result and what I see on Windows 10 is: position: 10, count: 20 result: 20 On Debian 10 I see: position: 10, count: 20 result: 16364 I believe transferFrom should never return more than the count passed to it, so this seems like a bug? I'm happy to give more information if needed. Note the Undertow buffer size is 16364. Also, on Debian it really did write 16364 bytes to the output channel. Cheers, -Nate int position = 10; int count = 20; StreamSinkChannel output = exchange.getResponseChannel(); FileChannel input = new RandomAccessFile(file, "r").getChannel(); while (count > 0) { long result; while (true) { System.out.println("position: " + position + ", count: " + count); result = output.transferFrom(input, position, count); System.out.println("result: " + result); // expected: <= 20 if (result!= 0L) break; try { output.awaitWritable(); } catch (InterruptedIOException ignored) { } } count -= result; position += result; }