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lzw-assignment
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better, but still some bugs

This commit is contained in:
Phuntsok Drak-pa 2018-06-17 06:38:57 +02:00
parent bae6d01bc8
commit 8777183821
3 changed files with 144 additions and 133 deletions
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256
src/bitpack.cc
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@ -10,108 +10,7 @@ using vuint16 = vector<uint16_t>;
using vuchar = vector<uchar>;
using ustring = std::basic_string<unsigned char>;
int max(const int t_n) {
return ipow(2, t_n) - 1;
}
///////////////////////////////////////////////////////////////////////////////
// packing //
///////////////////////////////////////////////////////////////////////////////
vuchar pack(const vuint16 &t_input) {
return pack_n(t_input.begin(), t_input.end(), 9);
}
/**
* Packs \p t_input into unsigned char, assuming the max value of t_input
* only takes \p t_n bits
*
* \param t_input_begin pointer to the beginning of the vector of values to be packed
* \param t_input_end pointer to the end of the input vector
* \param t_n maximum size of an input value in bits
* \return Returns a vector of unsigned char containing the packed values from t_input
*/
vuchar pack_n(const vuint16::const_iterator t_input_begin,
const vuint16::const_iterator t_input_end, const int t_n) {
if (t_n == 16) {
return pack_16(t_input_begin, t_input_end);
}
const int max_value = max(t_n); // max value held within t_n bits
#ifdef Debug
std::printf("%d bits! %ld chars remaining\n", t_n,
std::distance(t_input_begin, t_input_end));
std::printf("max: %d\n", max_value);
#endif
int step = t_n / 8;
int left_shift = 0;
int middle_shift = 0;
int right_shift = 0;
uchar current_char = 0;
bool char_touched = false;
vuchar ret{};
for (auto it = t_input_begin; it != t_input_end; ++it) {
if ((left_shift += step) >= t_n) {
left_shift = (left_shift - t_n) + step;
}
ret.push_back((current_char | (*it >> left_shift)) & 0xFFu);
// current_char = 0;
bool zero_right_shift = (right_shift == 0);
right_shift -= step;
if (right_shift < 0) {
middle_shift = std::abs(right_shift);
right_shift = 8 - std::abs(right_shift);
if (!zero_right_shift) {
current_char = (*it >> middle_shift) & 0xFFu;
ret.push_back(current_char);
}
}
if (right_shift == 0) {
current_char = *it & 0xffu;
ret.push_back(current_char);
current_char = 0;
char_touched = false;
} else {
current_char = (*it << right_shift) & 0xFFu;
char_touched = true;
}
// il faut écrire la valeur pour la décompression
if (*it >= max_value) {
if (char_touched) {
ret.push_back(current_char);
}
const auto next_vec = pack_n(it, t_input_end, t_n + 1);
ret.insert(ret.end(), next_vec.begin(), next_vec.end());
return ret;
}
}
if (char_touched) {
ret.push_back(current_char);
}
return ret;
}
vuchar pack_16(const vuint16::const_iterator t_input_begin,
const vuint16::const_iterator t_input_end) {
#ifdef Debug
std::printf("16 bits! %ld chars remaining\n",
std::distance(t_input_begin, t_input_end));
#endif
vuchar ret{};
std::for_each(t_input_begin, t_input_end, [&](const auto value) {
ret.push_back((value >> 8) & 0xFFu);
ret.push_back(value & 0xFFu);
});
return ret;
}
///////////////////////////////////////////////////////////////////////////////
// unpacking //
///////////////////////////////////////////////////////////////////////////////
int max(const int t_n) { return ipow(2, t_n) - 1; }
constexpr uint16_t mask_n(int t_nb_bits) {
if (t_nb_bits == 0) {
@ -128,60 +27,167 @@ constexpr uint16_t masks[17] = {
mask_n(6), mask_n(7), mask_n(8), mask_n(9), mask_n(10), mask_n(11),
mask_n(12), mask_n(13), mask_n(14), mask_n(15), mask_n(16)};
///////////////////////////////////////////////////////////////////////////////
// packing //
///////////////////////////////////////////////////////////////////////////////
vuchar pack(const vuint16 &t_input) {
return pack_n(t_input.begin(), t_input.end(), vuchar{}, 9);
}
/**
* Packs \p t_input into unsigned char, assuming the max value of t_input
* only takes \p t_n bits
*
* \param t_input_begin pointer to the beginning of the vector of values to be
* packed \param t_input_end pointer to the end of the input vector \param t_n
* maximum size of an input value in bits \return Returns a vector of unsigned
* char containing the packed values from t_input
*/
vuchar pack_n(const vuint16::const_iterator t_input_begin,
const vuint16::const_iterator t_input_end, vuchar t_res,
int t_n) {
if (t_n == 16) {
return pack_16(t_input_begin, t_input_end, vector<unsigned char>());
}
const int max_value = max(t_n); // max value held within t_n bits
#ifdef Debug
std::printf("%d bits! %ld chars remaining\n", t_n,
std::distance(t_input_begin, t_input_end));
std::printf("max: %d\n", max_value);
#endif
int step = t_n % 8;
int left_shift = 0;
int right_shift = 0;
uchar current_char = 0;
bool char_touched = false;
// pour chaque élément
for (auto it = t_input_begin; it != t_input_end; ++it) {
// si on a atteint ou dépassé la valeur maximale, on change de nombre de bits
if (*it >= max_value) {
// écriture du masque pour notifier à la décompression du changement de bits
if ((left_shift += step) >= t_n) {
left_shift = (left_shift - t_n) + step;
}
const auto mask = masks[t_n] >> left_shift;
t_res.push_back(
static_cast<uchar>(current_char | mask));
bool zero_rs = (right_shift == 0);
right_shift -= 0;
if(right_shift < 0) {
if(!zero_rs) {
current_char = static_cast<uchar>(masks[t_n] >> (-right_shift) & 0xffu);
t_res.push_back(current_char);
}
}
t_res.push_back(static_cast<uchar>(masks[t_n]));
return pack_n(it, t_input_end, t_res, t_n + 1);
}
if ((left_shift += step) >= t_n) {
left_shift = (left_shift - t_n) + step;
}
t_res.push_back(
static_cast<uchar>(current_char | (*it >> left_shift & 0xFFu)));
// current_char = 0;
bool zero_rs = (right_shift == 0);
right_shift -= step;
if (right_shift < 0) {
if (!zero_rs) {
current_char = static_cast<uchar>(*it >> (-right_shift) & 0xFFu);
t_res.push_back(current_char);
}
right_shift = 8 + right_shift;
}
if (right_shift == 0) {
current_char = static_cast<uchar>(*it & 0xffu);
t_res.push_back(current_char);
current_char = 0;
char_touched = false;
} else {
current_char = static_cast<uchar>(*it << right_shift & 0xFFu);
char_touched = true;
}
}
if (char_touched) {
t_res.push_back(current_char);
}
return t_res;
}
vuchar pack_16(const vuint16::const_iterator t_input_begin,
const vuint16::const_iterator t_input_end, vuchar t_res) {
#ifdef Debug
std::printf("16 bits! %ld chars remaining\n",
std::distance(t_input_begin, t_input_end));
#endif
std::for_each(t_input_begin, t_input_end, [&](const auto value) {
t_res.push_back((value >> 8) & 0xFFu);
t_res.push_back(value & 0xFFu);
});
return t_res;
}
///////////////////////////////////////////////////////////////////////////////
// unpacking //
///////////////////////////////////////////////////////////////////////////////
vuint16 unpack(ustring &&t_input) {
return unpack_n(t_input.begin(), t_input.end(), 9);
return unpack_n(t_input.begin(), t_input.end(), vuint16{}, 9);
}
vuint16 unpack_n(const ustring::const_iterator t_begin,
const ustring::const_iterator t_end, const int t_n) {
const ustring::const_iterator t_end, vuint16 t_res, int t_n) {
#ifdef Debug
std::printf("Chunk! %d bits, %ld compressed chars\n", t_n,
std::distance(t_begin, t_end));
#endif
if (t_n == 16) {
return unpack_16(t_begin, t_end);
return unpack_16(t_begin, t_end, vector<uint16_t>());
}
int step = t_n / 8;
int step = t_n % 8;
int left_shift = 0;
int right_shift = 0;
vuint16 ret{};
const int max_value = max(t_n);
for (auto it = t_begin; it < t_end - 1; /* nope */) {
uint16_t current_char = 0;
// left bits
left_shift =
((left_shift += step) >= t_n) ? (left_shift - t_n) + step : left_shift;
current_char = static_cast<uint16_t>(*it << left_shift);
if ((left_shift += step) >= t_n) {
left_shift = (left_shift - t_n) + step;
}
current_char = static_cast<uint16_t>(*it << left_shift) & masks[t_n];
// right bits
bool zero_rs = right_shift;
bool zero_rs = (right_shift == 0);
right_shift -= step;
if (right_shift < 0) {
// optional middle bits before right bits
if (zero_rs) {
current_char |= *++it << (-right_shift);
// if previous right shift was negative and not zero
if (!zero_rs) {
current_char |= *++it << (-right_shift) & masks[16 + right_shift];
}
right_shift = 8 + right_shift;
}
current_char |= *(++it) >> right_shift;
current_char |= *++it >> right_shift & masks[8 - right_shift];
// char made!
ret.push_back(current_char &= masks[t_n]);
if (current_char >= max_value) {
const auto next_vec = unpack_n(it + 1, t_end, t_n + 1);
ret.insert(ret.end(), next_vec.begin(), next_vec.end());
return ret;
if (current_char >= max_value) { // if it is the mask
return unpack_n(it + 1, t_end, t_res, t_n + 1);
}
t_res.push_back(current_char &= masks[t_n]);
if (right_shift == 0) {
++it;
}
}
return ret;
return t_res;
}
vuint16 unpack_16(const ustring::const_iterator t_begin,
const ustring::const_iterator t_end) {
vuint16 ret{};
const ustring::const_iterator t_end, vuint16 t_res) {
for (auto it = t_begin; it < t_end; ++it) {
ret.push_back(static_cast<uint16_t>((*it << 8) | *(++it)));
t_res.push_back(static_cast<uint16_t>(*it << 8 | *++it));
}
return ret;
return t_res;
}

18
src/bitpack.hh
View File

@ -15,22 +15,24 @@ std::vector<unsigned char> pack(const std::vector<std::uint16_t> &);
/// \brief Packs std::uint16_t of n bits into unsigned char
std::vector<unsigned char>
pack_n(const std::vector<std::uint16_t>::const_iterator,
const std::vector<std::uint16_t>::const_iterator, const int);
pack_n(std::vector<std::uint16_t>::const_iterator , std::vector<std::uint16_t>::const_iterator ,
std::vector<unsigned char> , int );
/// \brief Specialization of \ref pack_n for 16bits
std::vector<unsigned char>
pack_16(const std::vector<std::uint16_t>::const_iterator,
const std::vector<std::uint16_t>::const_iterator);
pack_16(std::vector<std::uint16_t>::const_iterator , std::vector<std::uint16_t>::const_iterator ,
std::vector<unsigned char> );
std::vector<std::uint16_t> unpack(std::basic_string<unsigned char> &&);
std::vector<std::uint16_t>
unpack_n(const std::basic_string<unsigned char>::const_iterator,
const std::basic_string<unsigned char>::const_iterator, const int t_n);
unpack_n(std::basic_string<unsigned char>::const_iterator t_begin,
std::basic_string<unsigned char>::const_iterator t_end,
std::vector<std::uint16_t> t_res, int t_n);
std::vector<std::uint16_t>
unpack_16(const std::basic_string<unsigned char>::const_iterator,
const std::basic_string<unsigned char>::const_iterator);
unpack_16(std::basic_string<unsigned char>::const_iterator,
std::basic_string<unsigned char>::const_iterator,
std::vector<std::uint16_t>);
#endif /* LZW_SRC_BITPACK_H_ */

3
src/uncompress.cc
View File

@ -24,6 +24,9 @@ ustring lzw_uncompress(vuint16 &&t_compressed) {
for (auto it = t_compressed.begin() + 1; it != t_compressed.end(); ++it) {
v = *it;
const auto uncompressed{dico_uncompress(dict, v, old)};
#ifdef Debug
std::printf("%d = %s\n", v, uncompressed.c_str());
#endif
ret.insert(ret.end(), uncompressed.begin(), uncompressed.end());
old = v;
}