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LibCompress: Change DeflateSpecialCodeLengths to constexpr variables

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This commit is contained in:
Lenny Maiorani 2022-03-29 14:52:06 -06:00 • committed by Linus Groh
parent 35af46ee62
commit 9afc7d5379
Notes: sideshowbarker 2024-07-17 14:32:50 +09:00
2 changed files with 17 additions and 19 deletions
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30
Userland/Libraries/LibCompress/Deflate.cpp
View file

@ -16,6 +16,10 @@
namespace Compress {
static constexpr u8 deflate_special_code_length_copy = 16;
static constexpr u8 deflate_special_code_length_zeros = 17;
static constexpr u8 deflate_special_code_length_long_zeros = 18;
CanonicalCode const& CanonicalCode::fixed_literal_codes()
{
static CanonicalCode code;
@ -441,21 +445,21 @@ void DeflateDecompressor::decode_codes(CanonicalCode& literal_code, Optional<Can
return;
}
if (symbol < DeflateSpecialCodeLengths::COPY) {
if (symbol < deflate_special_code_length_copy) {
code_lengths.append(static_cast<u8>(symbol));
continue;
} else if (symbol == DeflateSpecialCodeLengths::ZEROS) {
} else if (symbol == deflate_special_code_length_zeros) {
auto nrepeat = 3 + m_input_stream.read_bits(3);
for (size_t j = 0; j < nrepeat; ++j)
code_lengths.append(0);
continue;
} else if (symbol == DeflateSpecialCodeLengths::LONG_ZEROS) {
} else if (symbol == deflate_special_code_length_long_zeros) {
auto nrepeat = 11 + m_input_stream.read_bits(7);
for (size_t j = 0; j < nrepeat; ++j)
code_lengths.append(0);
continue;
} else {
VERIFY(symbol == DeflateSpecialCodeLengths::COPY);
VERIFY(symbol == deflate_special_code_length_copy);
if (code_lengths.is_empty()) {
set_fatal_error();
@ -819,11 +823,11 @@ size_t DeflateCompressor::dynamic_block_length(Array<u8, max_huffman_literals> c
auto frequency = code_lengths_frequencies[i];
length += code_lengths_bit_lengths[i] * frequency;
if (i == DeflateSpecialCodeLengths::COPY) {
if (i == deflate_special_code_length_copy) {
length += 2 * frequency;
} else if (i == DeflateSpecialCodeLengths::ZEROS) {
} else if (i == deflate_special_code_length_zeros) {
length += 3 * frequency;
} else if (i == DeflateSpecialCodeLengths::LONG_ZEROS) {
} else if (i == deflate_special_code_length_long_zeros) {
length += 7 * frequency;
}
}
@ -869,10 +873,10 @@ size_t DeflateCompressor::encode_huffman_lengths(Array<u8, max_huffman_literals
}
if (zero_count <= 10) {
encoded_lengths[encoded_count].symbol = DeflateSpecialCodeLengths::ZEROS;
encoded_lengths[encoded_count].symbol = deflate_special_code_length_zeros;
encoded_lengths[encoded_count++].count = zero_count;
} else {
encoded_lengths[encoded_count].symbol = DeflateSpecialCodeLengths::LONG_ZEROS;
encoded_lengths[encoded_count].symbol = deflate_special_code_length_long_zeros;
encoded_lengths[encoded_count++].count = zero_count;
}
i += zero_count;
@ -886,7 +890,7 @@ size_t DeflateCompressor::encode_huffman_lengths(Array<u8, max_huffman_literals
copy_count++;
if (copy_count >= 3) {
encoded_lengths[encoded_count].symbol = DeflateSpecialCodeLengths::COPY;
encoded_lengths[encoded_count].symbol = deflate_special_code_length_copy;
encoded_lengths[encoded_count++].count = copy_count;
i += copy_count;
continue;
@ -935,11 +939,11 @@ void DeflateCompressor::write_dynamic_huffman(CanonicalCode const& literal_code,
for (size_t i = 0; i < encoded_lengths_count; i++) {
auto encoded_length = encoded_lengths[i];
code_lengths_code->write_symbol(m_output_stream, encoded_length.symbol);
if (encoded_length.symbol == DeflateSpecialCodeLengths::COPY) {
if (encoded_length.symbol == deflate_special_code_length_copy) {
m_output_stream.write_bits(encoded_length.count - 3, 2);
} else if (encoded_length.symbol == DeflateSpecialCodeLengths::ZEROS) {
} else if (encoded_length.symbol == deflate_special_code_length_zeros) {
m_output_stream.write_bits(encoded_length.count - 3, 3);
} else if (encoded_length.symbol == DeflateSpecialCodeLengths::LONG_ZEROS) {
} else if (encoded_length.symbol == deflate_special_code_length_long_zeros) {
m_output_stream.write_bits(encoded_length.count - 11, 7);
}
}

6
Userland/Libraries/LibCompress/Deflate.h
View file

@ -103,12 +103,6 @@ private:
CircularDuplexStream<32 * KiB> m_output_stream;
};
enum DeflateSpecialCodeLengths : u32 {
COPY = 16,
ZEROS = 17,
LONG_ZEROS = 18
};
class DeflateCompressor final : public OutputStream {
public:
static constexpr size_t block_size = 32 * KiB - 1; // TODO: this can theoretically be increased to 64 KiB - 2