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Include the header in the tdigest serialize buffer size #563

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Merged
proost merged 1 commit into from
Oct 30, 2026
Merged

Include the header in the tdigest serialize buffer size #563

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2 changes: 1 addition & 1 deletion tdigest/include/tdigest_impl.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -378,7 +378,7 @@ size_t tdigest<T, A>::get_serialized_size_bytes(bool with_buffer) const {
template<typename T, typename A>
auto tdigest<T, A>::serialize(unsigned header_size_bytes, bool with_buffer) const -> vector_bytes {
if (!with_buffer) const_cast<tdigest*>(this)->compress(); // side effect
vector_bytes bytes(get_serialized_size_bytes(with_buffer), 0, buffer_.get_allocator());
vector_bytes bytes(header_size_bytes + get_serialized_size_bytes(with_buffer), 0, buffer_.get_allocator());
uint8_t* ptr = bytes.data() + header_size_bytes;
*ptr++ = get_preamble_longs();
*ptr++ = SERIAL_VERSION;
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22 changes: 22 additions & 0 deletions tdigest/test/tdigest_test.cpp
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Expand Up @@ -18,6 +18,7 @@
*/

#include <catch2/catch.hpp>
#include <algorithm>
#include <cmath>
#include <cstdint>
#include <cstring>
Expand Down Expand Up @@ -347,6 +348,27 @@ TEST_CASE("serialize deserialize bytes many values with buffer", "[tdigest]") {
REQUIRE(td.get_quantile(0.5) == deserialized_td.get_quantile(0.5));
}

TEST_CASE("serialize bytes with header", "[tdigest]") {
const unsigned header_size_bytes = 7;
auto check = [header_size_bytes](const tdigest<double>& td, bool with_buffer) {
auto bytes = td.serialize(header_size_bytes, with_buffer);
auto bytes_no_header = td.serialize(0, with_buffer);
REQUIRE(bytes.size() == header_size_bytes + bytes_no_header.size());
REQUIRE(bytes.size() == header_size_bytes + td.get_serialized_size_bytes(with_buffer));
REQUIRE(std::equal(bytes_no_header.begin(), bytes_no_header.end(), bytes.begin() + header_size_bytes));
auto deserialized_td = tdigest<double>::deserialize(bytes.data() + header_size_bytes, bytes.size() - header_size_bytes);
REQUIRE(td.get_total_weight() == deserialized_td.get_total_weight());
};
tdigest<double> td(100);
check(td, false);
td.update(123);
check(td, false);
check(td, true);
for (int i = 0; i < 10000; ++i) td.update(i);
check(td, true);
check(td, false);
}

TEST_CASE("serialize deserialize steam and bytes equivalence empty", "[tdigest]") {
tdigest<double> td(100);
std::stringstream s(std::ios::in | std::ios::out | std::ios::binary);
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