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perf(cpp): skip LZ4 frame checksums (XXH32) for a measurable throughp… #1742

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perf(cpp): skip LZ4 frame checksums (XXH32) for a measurable throughp… #1742

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9 changes: 8 additions & 1 deletion cpp/mcap/include/mcap/reader.inl
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Original file line number Diff line number Diff line change
Expand Up @@ -208,8 +208,15 @@ Status LZ4Reader::decompressAll(const std::byte* data, uint64_t compressedSize,
size_t dstSize = uncompressedSize;
size_t srcSize = compressedSize;
LZ4F_resetDecompressionContext((LZ4F_dctx*)decompressionContext_);
// Skip XXH32 block/content-checksum verification for a measurable throughput
// gain on trusted files. Profiling a point-cloud-heavy MCAP showed
// LZ4_XXH32_update costing more than the decompression itself (~12% vs ~9%
// of total GUI-thread CPU). Structural corruption is still caught by the
// size/consumption checks below.
LZ4F_decompressOptions_t decompressOptions = {};
decompressOptions.skipChecksums = 1;
const auto status = LZ4F_decompress((LZ4F_dctx*)decompressionContext_, output->data(), &dstSize,
data, &srcSize, nullptr);
data, &srcSize, &decompressOptions);
if (status != 0) {
if (LZ4F_isError(status)) {
const auto msg = internal::StrCat("lz4 decompression of ", compressedSize, " bytes into ",
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