10539f4dc7
Motivation: CompositeByteBuf is a powerful and versatile abstraction, allowing for manipulation of large data without copying bytes. There is still a non-negligible cost to reading/writing however relative to "singular" ByteBufs, and this can be mostly eliminated with some rework of the internals. My use case is message modification/transformation while zero-copy proxying. For example replacing a string within a large message with one of a different length Modifications: - No longer slice added buffers and unwrap added slices - Components store target buf offset relative to position in composite buf - Less allocations, object footprint, pointer indirection, offset arithmetic - Use Component[] rather than ArrayList<Component> - Avoid pointer indirection and duplicate bounds check, more efficient backing array growth - Facilitates optimization when doing bulk-inserts - inserting n ByteBufs behind m is now O(m + n) instead of O(mn) - Avoid unnecessary casting and method call indirection via superclass - Eliminate some duplicate range/ref checks via non-checking versions of toComponentIndex and findComponent - Add simple fast-path for toComponentIndex(0); add racy cache of last-accessed Component to findComponent(int) - Override forEachByte0(...) and forEachByteDesc0(...) methods - Make use of RecyclableArrayList in nioBuffers(int, int) (in line with FasterCompositeByteBuf impl) - Modify addComponents0(boolean,int,Iterable) to use the Iterable directly rather than copy to an array first (and possibly to an ArrayList before that) - Optimize addComponents0(boolean,int,ByteBuf[],int) to not perform repeated array insertions and avoid second loop for offset updates - Simplify other logic in various places, in particular the general pattern used where a sub-range is iterated over - Add benchmarks to demonstrate some improvements While refactoring I also came across a couple of clear bugs. They are fixed in these changes but I will open another PR with unit tests and fixes to the current version. Result: Much faster creation, manipulation, and access; many fewer allocations and smaller footprint. Benchmark results to follow. |
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