Fixed bit-packing bug
This commit is contained in:
Phuntsok Drak-pa
parent
5b9f3ccd6a
commit
2b3e5e3f2b
@ -1,7 +1,7 @@
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#include "bitpack.hh"
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#include "common.hh"
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#include <cmath>
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#include <algorithm>
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#include <cmath>
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using std::uint16_t;
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using std::vector;
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@ -22,37 +22,38 @@ vuchar pack(const vuint16 &t_input) {
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* Packs \p t_input into unsigned char, assuming the max value of t_input
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* only takes \p t_n bits
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*
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* \param t_input_begin pointer to the beginning of the vector of values to
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* be packed \param t_input_end pointer to the end of the input vector
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* \param t_n maximum size of an input value in bits \return Returns a
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* vector of unsigned char containing the packed values from t_input
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* \param t_input_begin pointer to the beginning of the vector of values to be packed
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* \param t_input_end pointer to the end of the input vector
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* \param t_n maximum size of an input value in bits
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* \return Returns a vector of unsigned char containing the packed values from t_input
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*/
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vuchar pack_n(const vuint16::const_iterator t_input_begin,
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const vuint16::const_iterator t_input_end, const int t_n) {
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#ifdef Debug
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std::printf("%d bits!\n", t_n);
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#endif
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if (t_n == 16) {
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return pack_16(t_input_begin, t_input_end);
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}
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vuchar ret{};
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const int max_value = ipow(2, t_n) - 1; // max value held within t_n bits
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// max value with current number of bits + 1
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const int max_value = ipow(2, t_n) - 1;
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#ifdef Debug
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std::printf("%d bits! %ld chars remaining\n", t_n,
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std::distance(t_input_begin, t_input_end));
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std::printf("max: %d\n", max_value);
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#endif
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uchar current_char = 0;
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int step = t_n / 8;
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int left_shift = 0;
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int middle_shift = 0;
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int right_shift = 0;
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uchar current_char = 0;
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bool char_touched = false;
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vuchar ret{};
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for (auto it = t_input_begin; it != t_input_end; ++it) {
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left_shift += step;
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if (left_shift >= t_n) {
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if ((left_shift += step) >= t_n) {
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left_shift = (left_shift - t_n) + step;
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}
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ret.push_back((current_char | (*it >> left_shift)) & 0xFFu);
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current_char = 0;
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// current_char = 0;
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bool zero_right_shift = (right_shift == 0);
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right_shift -= step;
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@ -60,19 +61,23 @@ vuchar pack_n(const vuint16::const_iterator t_input_begin,
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middle_shift = std::abs(right_shift);
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right_shift = 8 - std::abs(right_shift);
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if (!zero_right_shift) {
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ret.push_back((*it >> middle_shift) & 0xFF);
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current_char = (*it >> middle_shift) & 0xFFu;
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ret.push_back(current_char);
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}
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}
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if (right_shift == 0) {
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ret.push_back(*it & 0xff);
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current_char = *it & 0xffu;
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ret.push_back(current_char);
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current_char = 0;
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char_touched = false;
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} else {
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current_char = (*it << right_shift) & 0xFF;
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current_char = (*it << right_shift) & 0xFFu;
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char_touched = true;
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}
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// at the end so we can detect `max_value` while parsing for bit-unpacking
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if (*t_input_end >= max_value) {
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if (current_char != 0) {
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// il faut écrire la valeur pour la décompression
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if (*it >= max_value) {
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if (char_touched) {
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ret.push_back(current_char);
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}
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const auto next_vec = pack_n(it, t_input_end, t_n + 1);
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@ -80,7 +85,7 @@ vuchar pack_n(const vuint16::const_iterator t_input_begin,
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return ret;
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}
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}
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if (current_char != 0) {
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if (char_touched) {
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ret.push_back(current_char);
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}
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return ret;
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@ -88,10 +93,14 @@ vuchar pack_n(const vuint16::const_iterator t_input_begin,
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vuchar pack_16(const vuint16::const_iterator t_input_begin,
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const vuint16::const_iterator t_input_end) {
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#ifdef Debug
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std::printf("16 bits! %ld chars remaining\n",
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std::distance(t_input_begin, t_input_end));
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#endif
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vuchar ret{};
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std::for_each(t_input_begin, t_input_end, [&](const auto value) {
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ret.push_back((value >> 8) & 0xFF);
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ret.push_back(value & 0xFF);
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ret.push_back((value >> 8) & 0xFFu);
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ret.push_back(value & 0xFFu);
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});
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return ret;
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}
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@ -100,27 +109,38 @@ vuchar pack_16(const vuint16::const_iterator t_input_begin,
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// unpacking //
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///////////////////////////////////////////////////////////////////////////////
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uint16_t mask_n(int t_nb_bits) {
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constexpr uint16_t mask_n(int t_nb_bits) {
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if (t_nb_bits == 0) {
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return 0;
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}
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uint16_t mask = mask_n(t_nb_bits - 1);
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mask <<= 1;
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mask = static_cast<uint16_t>(mask << 1);
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mask |= 0x1;
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return mask;
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}
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constexpr uint16_t masks[17] = {
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mask_n(0), mask_n(1), mask_n(2), mask_n(3), mask_n(4), mask_n(5),
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mask_n(6), mask_n(7), mask_n(8), mask_n(9), mask_n(10), mask_n(11),
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mask_n(12), mask_n(13), mask_n(14), mask_n(15), mask_n(16)};
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vuint16 unpack(ustring &&t_input) {
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return unpack_n(t_input.begin(), t_input.end(), 9);
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}
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vuint16 unpack_n(const ustring::const_iterator t_begin,
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const ustring::const_iterator t_end, const int t_n) {
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#ifdef Debug
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std::printf("Chunk! %d bits, %ld compressed chars\n", t_n,
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std::distance(t_begin, t_end));
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#endif
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if (t_n == 16) {
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return unpack_16(t_begin, t_end);
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}
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int step = t_n / 8;
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int left_shift = 0;
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int right_shift = 0;
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vuint16 ret{};
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const uint16_t mask = mask_n(t_n);
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const int max_value = ipow(2, t_n);
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for (auto it = t_begin; it < t_end - 1; /* nope */) {
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uint16_t current_char = 0;
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@ -134,21 +154,21 @@ vuint16 unpack_n(const ustring::const_iterator t_begin,
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if (right_shift < 0) {
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// optional middle bits before right bits
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if (zero_rs) {
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current_char |= *++it << std::abs(right_shift);
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current_char |= *++it << (-right_shift);
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}
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right_shift = 8 - std::abs(right_shift);
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right_shift = 8 + right_shift;
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}
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current_char |= *(++it) >> right_shift;
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// char made!
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ret.push_back(current_char &= mask);
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if (right_shift == 0) {
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++it;
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}
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ret.push_back(current_char &= masks[t_n]);
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if (current_char >= max_value) {
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const auto next_vec = unpack_n(it, t_end, t_n + 1);
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const auto next_vec = unpack_n(it + 1, t_end, t_n + 1);
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ret.insert(ret.end(), next_vec.begin(), next_vec.end());
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return ret;
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}
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if (right_shift == 0) {
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++it;
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}
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}
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return ret;
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}
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@ -65,9 +65,6 @@ ustring dico_uncompress(std::map<uint16_t, ustring> &t_dict,
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const uint16_t t_code, const uint16_t t_old) {
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// le code existe dans le dictionnaire s’il est < 256
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if (t_code < 256) {
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#ifdef Debug
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std::printf("Code : %d\tNOT EMPTY\n", t_code);
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#endif
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ustring e{static_cast<unsigned char>(t_code)};
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// 256 car on n'a pas encore tenté d'insérer de nouveau caractère
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if (t_old < 256) {
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@ -85,19 +82,13 @@ ustring dico_uncompress(std::map<uint16_t, ustring> &t_dict,
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// le code existe dans le dictionnaire
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if (!e.empty()) {
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#ifdef Debug
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std::printf("Code : %d\tNOT EMPTY\n", t_code);
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#endif
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str += e[0];
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const uint16_t index = static_cast<uint16_t>(t_dict.size() + 256);
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const auto index = static_cast<uint16_t>(t_dict.size() + 256);
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t_dict[index] = str;
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return e;
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}
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// le code n'existe pas encore dans le dictionnaire
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#ifdef Debug
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std::printf("Code : %d\tEMPTY\n", t_code);
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#endif
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str += str[0];
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e = str;
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t_dict[t_code] = e;
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@ -77,7 +77,6 @@ void compress(const std::string &t_in_file, const char *t_out_file) {
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if (out == nullptr) {
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std::cerr << "Error at " << __FILE__ << ":" << __LINE__ - 4
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<< ": could not open output file. Aborting...\n";
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// input_file.close();
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std::fclose(input_file);
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exit(1);
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}
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