Motivation:
Lz4FrameEncoder and Lz4FrameDecoder in their default configuration use
an extremely inefficient way to checksum direct byte buffers. In
particular, for every byte checksummed, a single-element byte array is
being allocated and a JNI cal is made, which in some internal testing
makes a 25x difference in total throughput and allocates *a lot* of
garbage.
Modifications:
Lz4XXHash32, an implementation of ByteBufChecksum specifically for use
by Lz4FrameEncoder and Lz4FrameDecoder, is introduced. It utilises
xxHash32 block API which provides a hash() method that accepts a
ByteBuffer as an argument. Lz4FrameEncoder and Lz4FrameDecoder are
modified to use this implementation by default.
Result:
Lz4FrameEncoder and Lz4FrameDecoder perform well again when operating
on direct byte buffers with default checksum configuration; a public
implementation is provided for those who need to override the seed.
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