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[coding] Added varint short arrays ser/des.

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Signed-off-by: Viktor Govako <viktor.govako@gmail.com>

# Conflicts:
#	libs/coding/coding_tests/varint_test.cpp
This commit is contained in:
Viktor Govako
2025-07-05 11:19:30 -03:00
committed by Konstantin Pastbin
parent 111e913478
commit 25a4a3b76f
2 changed files with 77 additions and 6 deletions
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54
libs/coding/varint.hpp
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@@ -3,13 +3,10 @@
#include "coding/write_to_sink.hpp"
#include "base/assert.hpp"
#include "base/base.hpp"
#include "base/bits.hpp"
#include "base/exception.hpp"
#include "base/stl_helpers.hpp"
#include <cstddef>
#include <cstdint>
#include <type_traits>
// Writes any unsigned integer type using optimal bytes count, platform-independent.
@@ -296,6 +293,53 @@ void const * ReadVarUint64Array(void const * pBeg, size_t count, F f)
template <class Cont, class Sink>
void WriteVarUintArray(Cont const & v, Sink & sink)
{
for (size_t i = 0; i != v.size(); ++i)
WriteVarUint(sink, v[i]);
for (auto e : v)
WriteVarUint(sink, e);
}
/// @name Special functions to read/write varint array when each value stores a control bit "has next".
/// Useful for short (>90% have 1 value) arrays.
/// @{
template <class Sink>
void WriteVarUInt32SortedShortArray(std::vector<uint32_t> const & cont, Sink & sink)
{
CHECK(!cont.empty(), ());
CHECK(base::IsSortedAndUnique(cont), ());
uint32_t prev = 0;
size_t const sz = cont.size();
for (size_t i = 0; i < sz; ++i)
{
uint32_t v = cont[i] - prev;
prev = cont[i];
CHECK((v & (uint32_t(3) << 30)) == 0, ()); // leading 2 bits are zeros
v <<= 1;
// set 1-bit if have a next value
if (i + 1 < sz)
v |= 0x1;
WriteVarUint(sink, v);
}
}
/// @todo Refactor on raw pointers (same as ReadXXX functions above).
/// ArrayByteSource isn't as fast as pointers :)
template <class Source, class ContT>
void ReadVarUInt32SortedShortArray(Source & src, ContT & cont)
{
cont.clear();
bool hasNext = false;
uint32_t prev = 0;
do
{
uint32_t const v = ReadVarUint<uint32_t>(src);
hasNext = (v & 0x1) != 0;
prev += (v >> 1);
cont.push_back(prev);
}
while (hasNext);
}
/// @}