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Changed file writing method to dynamic bit-packing

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This commit is contained in:
Phuntsok Drak-pa 2018-06-09 03:18:28 +02:00
parent d901cd60f2
commit 6d779d8606
3 changed files with 10 additions and 17 deletions
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2
src/bitpack.cc
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@ -40,7 +40,7 @@ vuchar pack_n(const vuint16::const_iterator t_input_begin,
vuchar ret{};
// max value with current number of bits + 1
const int max_value = ipow(2, t_n);
const int max_value = ipow(2, t_n) - 1;
uchar current_char = 0;
int step = t_n / 8;

3
src/bitpack.hh
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@ -19,4 +19,7 @@ std::vector<unsigned char>
pack_16(const std::vector<std::uint16_t>::const_iterator,
const std::vector<std::uint16_t>::const_iterator);
/// \brief Bat-packs the input dynamically
std::vector<unsigned char> pack(const std::vector<std::uint16_t>);
#endif /* LZW_SRC_BITPACK_H_ */

22
src/io.cc
View File

@ -4,7 +4,9 @@
*/
#include "io.hh"
#include "bitpack.hh"
#include <array>
#include <algorithm>
#ifdef Debug
constexpr bool debug_mode = true;
@ -71,21 +73,9 @@ void write_file(FILE *const t_out, const vvuint16 &t_text) {
* \param t_chunk Chunk to be written to \p t_out
*/
void write_chunk(FILE *const t_out, const vuint16 &t_chunk) {
const auto chunk_size = static_cast<uint16_t>(t_chunk.size());
const auto output = pack(t_chunk);
const auto chunk_size = static_cast<uint16_t>(output.size());
fwrite(&chunk_size, sizeof(chunk_size), 1, t_out);
std::array<unsigned char, 3> data = {0, 0, 0};
for (size_t i = 0; i < t_chunk.size(); ++i) {
if (i % 2 == 0) {
data[0] = static_cast<unsigned char>(t_chunk[i] >> 4);
data[1] = static_cast<unsigned char>(t_chunk[i] << 4);
} else {
data[1] |= static_cast<unsigned char>(t_chunk[i] >> 8) & 0xC;
data[2] = static_cast<unsigned char>(t_chunk[i]);
fwrite(data.data(), sizeof(data[0]), 3, t_out);
data.fill(0);
}
}
if (t_chunk.size() % 2 != 0) {
fwrite(data.data(), sizeof(data[0]), 3, t_out);
}
fwrite((const char *)(output.data()), sizeof(output[0]), output.size(),
t_out);
}