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#pragma once
#include "coding/bit_streams.hpp"
#include "base/assert.hpp"
#include "base/bits.hpp"
#include "std/cstdint.hpp"
namespace coding
{
class GammaCoder
{
public:
template <typename TWriter>
static bool Encode(BitWriter<TWriter> & writer, uint64_t value)
{
if (value == 0)
return false;
uint8_t const n = bits::FloorLog(value);
ASSERT_LESS_OR_EQUAL(n, 63, ());
uint64_t const msb = static_cast<uint64_t>(1) << n;
writer.WriteAtMost64Bits(msb, n + 1);
writer.WriteAtMost64Bits(value, n);
return true;
}
template <typename TReader>
static uint64_t Decode(BitReader<TReader> & reader)
{
uint8_t n = 0;
while (reader.Read(1) == 0)
++n;
ASSERT_LESS_OR_EQUAL(n, 63, ());
uint64_t const msb = static_cast<uint64_t>(1) << n;
return msb | reader.ReadAtMost64Bits(n);
}
};
class DeltaCoder
{
public:
template <typename TWriter>
static bool Encode(BitWriter<TWriter> & writer, uint64_t value)
{
if (value == 0)
return false;
uint8_t const n = bits::FloorLog(value);
ASSERT_LESS_OR_EQUAL(n, 63, ());
if (!GammaCoder::Encode(writer, n + 1))
return false;
writer.WriteAtMost64Bits(value, n);
return true;
}
template <typename TReader>
static uint64_t Decode(BitReader<TReader> & reader)
{
uint8_t n = GammaCoder::Decode(reader);
ASSERT_GREATER(n, 0, ());
--n;
ASSERT_LESS_OR_EQUAL(n, 63, ());
uint64_t const msb = static_cast<uint64_t>(1) << n;
return msb | reader.ReadAtMost64Bits(n);
}
};
} // namespace coding
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