Thread-safe Content.Chunk#slice

[gregw]

Jetty version(s)
12

Description

The implementation of Content.Chunk#slice(int,int,boolean) is not threadsafe.

If multiple threads are slicing off the same chunk, then incorrect results may occur as each thread modifies the pointers of the original chunk. It should be able to use the ByteBuffer#slice(int,int) method to slice without modifying the original buffer.

[gregw]

I think the implementation can be something like:

        default Chunk slice(int position, int limit, boolean last)
        {
            ByteBuffer sourceBuffer = getByteBuffer();
            if (position == limit)
                return last && limit == sourceBuffer.limit() ? EOF : EMPTY;
            return from(sourceBuffer.slice(position, limit - position), last, this);
        }

Note that if we slice an empty chunk of a non empty last chunk, then I think it should be last only if it is slicing at the limit. Hence the extra check on EOF vs EMPTY.

[gregw]

Actually, the last is passed in, so it doesn't matter about the limit. The implementation should be just:

        default Chunk slice(int position, int limit, boolean last)
        {
            ByteBuffer sourceBuffer = getByteBuffer();
            if (position == limit)
                return last ? EOF : EMPTY;
            return from(sourceBuffer.slice(position, limit - position), last, this);
        }