clyne/consteval-huffman
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Optimized decoder increment

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Clyne 2020-12-27 19:03:37 -05:00 committed by GitHub
parent cfbe244e90
commit 4a81241a82
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GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 13 additions and 7 deletions
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20
consteval_huffman.hpp
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@ -9,6 +9,7 @@
#include <algorithm>
#include <span>
#include <string>
/**
* Compresses the given data string using Huffman coding, providing a
@ -244,7 +245,7 @@ public:
if constexpr (bytes_saved() > 0) {
const auto [size_bytes, last_bits] = m_data->compressed_size_info();
m_pos = size_bytes - 1;
m_bit = 8 - last_bits;
m_bit = 1 << (7 - last_bits);
} else {
m_pos = data_length + 1;
}
@ -253,7 +254,7 @@ public:
}
bool operator==(const decode_info& other) const {
return m_data == other.m_data && m_bit == other.m_bit && m_pos == other.m_pos;
return m_bit == other.m_bit && m_pos == other.m_pos;
}
auto operator*() const {
return m_current;
@ -272,12 +273,17 @@ public:
void get_next() {
if constexpr (bytes_saved() > 0) {
auto *node = m_data->decode_tree;
auto pos = m_pos;
auto bit = m_bit;
do {
bool bit = m_data->compressed_data[m_pos] & (1 << (m_bit - 1));
if (--m_bit == 0)
m_bit = 8, m_pos++;
node += 3 * node[bit ? 2 : 1];
auto idx = (m_data->compressed_data[pos] & bit) ? 2u : 1u;
node += node[idx] * 3u;
bit >>= 1;
if (!bit)
bit = 0x80, pos++;
} while (node[1] != 0);
m_pos = pos;
m_bit = bit;
m_current = *node;
} else {
m_current = data[m_pos++];
@ -286,7 +292,7 @@ public:
const huffman_compress<data> *m_data = nullptr;
size_t m_pos = 0;
unsigned char m_bit = 8;
unsigned char m_bit = 0x80;
int m_current = -1;
friend class huffman_compress;