[io] Write byte counts in streamer field#22430
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The version 0 and version 1 streamer fields are exactly the same for small objects (<=1GiB). For larger objects, the version 1 streamer field stores the byte count stack before the data. This is up to a future patch. For the moment, we assert that the streamed buffer is never >1GiB.
jblomer
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Test Results 22 files 22 suites 3d 10h 28m 44s ⏱️ For more details on these failures, see this check. Results for commit 3b67b13. ♻️ This comment has been updated with latest results. |
Add version 1 streamer field.
Uses RStreamerField as a test bed for (de-)serializing large objects with TBufferFile.
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hahnjo
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| if (static_cast<std::size_t>(nbytes) > kMaxSmallBuffer) { | ||
| throw RException(R__FAIL("large objects (>1GiB) not supported by the version 0 streamer field")); | ||
| } else { | ||
| assert(buffer.GetByteCounts().empty()); |
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For back-/forwards-porting this assert will have to be removed...
| Both versions have an identical on-disk representation when the streamed object is smaller than 1GiB. | ||
| Only version 1 supports larger streamed objects. | ||
| For large objects, the version 1 streamer field prepends the large byte counts ("byte count stack") to the byte stream. | ||
| The format for the version 1 byte stream is |
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For objects bigger than 1 GiB, the format [...] is:
| The format for the version 1 byte stream is | ||
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| - 64bit unsigned integer: number of elements in the large byte count list | ||
| - List if 64bit unsigned integer pairs with the byte count location and byte count value` |
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"List of" plus stray backtick at the end of the line
| const std::size_t szBufCounts = sizeof(std::uint64_t) * (2 * nCounts + 1); | ||
| if (szBufCounts > nbytes) | ||
| throw RException(R__FAIL("invalid byte count size in streamer field: " + std::to_string(nCounts))); | ||
| bufCounts.resize(szBufCounts); |
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This will zero-initialize the elements. Maybe use Internal::MakeUninitArray as for writing?
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| std::vector<unsigned char> bufCounts(sizeof(std::uint64_t)); | ||
| fAuxiliaryColumn->ReadV(collectionStart, sizeof(std::uint64_t), bufCounts.data()); | ||
| std::uint64_t nCounts; | ||
| std::size_t pos = Internal::RNTupleSerializer::DeserializeUInt64(bufCounts.data(), nCounts); |
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If using Internal::MakeUninitArray below, this could be a static array on the stack
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| namespace { | ||
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| class FileRaii { |
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We have this in tree/ntuple/test/ntuple_test.hxx, no?
pcanal
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Jun 3, 2026
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| using ByteCountLocator_t = std::size_t; // This might become a pair<chunk_number, local_offset> if we implement chunked keys | ||
| using ByteCount_t = std::uint64_t; ///< Type used to store byte count values, can be changed to uint32_t if we implement chunked keys |
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| using ByteCountLocator_t = std::size_t; // This might become a pair<chunk_number, local_offset> if we implement chunked keys | |
| using ByteCount_t = std::uint64_t; ///< Type used to store byte count values, can be changed to uint32_t if we implement chunked keys | |
| using ByteCountLocator_t = std::size_t; ///< This might become a pair<chunk_number, local_offset> if we implement chunked keys | |
| using ByteCount_t = std::uint64_t; ///< Type used to store byte count values, can be changed to uint32_t if we implement chunked keys |
pcanal
reviewed
Jun 3, 2026
| throw RException(R__FAIL("invalid byte count size in streamer field: " + std::to_string(nCounts))); | ||
| const std::size_t szBufCounts = sizeof(std::uint64_t) * (2 * nCounts + 1); | ||
| if (szBufCounts > nbytes) | ||
| throw RException(R__FAIL("invalid byte count size in streamer field: " + std::to_string(nCounts))); |
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Should this mention szBufCounts (and nbytes) instead of nCounts?
pcanal
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Jun 3, 2026
| ClassDefNV(MemberWithCustomStreamer, 2); | ||
| }; | ||
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| struct VersionedStreamerField |
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Out of curiosity, are the test related to the VersionedStreamerField linked to the large object streaming test or 'just' nice unrelated additions?
pcanal
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Jun 3, 2026
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| EXPECT_EQ(-1, ptr->fOne.at(1000)); | ||
| EXPECT_EQ(100000000u, ptr->fTwo.size()); | ||
| EXPECT_EQ(-2, ptr->fTwo.at(2000)); |
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We may want to also test an element towards the end for the vector.
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Adds support for streamer field v1, which writes the byte counts of large objects into the stream.
The first two commits should be backported.
Replaces #20608