Buffer.truncate(size)

I found myself in a situation today where it was more efficient to write extra data (in the form of SegmentedByteStrings) to a buffer and truncate the buffer. Currently, I’m doing it this way:

long oldSize = sink.size();
long toWrite = Math.min(byteCount, SEGMENT_SIZE);
// ... maybe other writes
sink.write(segmentTemplate); // might overfill the buffer
sink.readAndWriteUnsafe(cursor);
try {
    cursor.resizeBuffer(oldSize + toWrite);
} finally {
    cursor.close();
}

This would also be alleviated if there was better handling of ByteStrings substrings. Either make creating substrings of a SegementedByteString share the underlying segments or add a BufferedSink.write method which allows for a begin and end index when writing a ByteString. Probably all good things regardless?

[swankjesse]

As a general rule I prefer all Buffer changes to be either reading from the front or writing to the end. You can cheat to truncate like so:

Buffer needsToTruncate = ...
long truncatedLength = ...;
Buffer temp = new Buffer();
temp.write(needsToTruncate, truncatedLength);
needsToTruncate.clear();
needsToTruncate.writeAll(temp);

I wonder which of the two variants will perform better. One of ’em might share segments better than the other.

[bnorm]

No worries, I sort of jumped topics pretty quick there. Closing as the original request is not going to be implemented.