src/base/bittorrent/ltqbitarray.cpp

   1 /*
   2  * Bittorrent Client using Qt and libtorrent.
   3  * Copyright (C) 2022  Mike Tzou (Chocobo1)
   4  *
   5  * This program is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU General Public License
   7  * as published by the Free Software Foundation; either version 2
   8  * of the License, or (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, write to the Free Software
  17  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  18  *
  19  * In addition, as a special exception, the copyright holders give permission to
  20  * link this program with the OpenSSL project's "OpenSSL" library (or with
  21  * modified versions of it that use the same license as the "OpenSSL" library),
  22  * and distribute the linked executables. You must obey the GNU General Public
  23  * License in all respects for all of the code used other than "OpenSSL".  If you
  24  * modify file(s), you may extend this exception to your version of the file(s),
  25  * but you are not obligated to do so. If you do not wish to do so, delete this
  26  * exception statement from your version.
  27  */
  28
  29 #include "ltqbitarray.h"
  30
  31 #include <libtorrent/bitfield.hpp>
  32
  33 #include <QBitArray>
  34 #include <QVarLengthArray>
  35
  36 namespace
  37 {
  38     unsigned char reverseByte(const unsigned char byte)
  39     {
  40         // https://graphics.stanford.edu/~seander/bithacks.html#BitReverseTable
  41         static const unsigned char table[] =
  42         {
  43 #define R2(n) n, (n + (2 * 64)), (n + 64), (n + (3 * 64))
  44 #define R4(n) R2(n), R2(n + (2 * 16)), R2(n + 16), R2(n + (3 * 16))
  45 #define R6(n) R4(n), R4(n + (2 * 4)), R4(n + 4), R4(n + (3 * 4))
  46             R6(0), R6(2), R6(1), R6(3)
  47 #undef R6
  48 #undef R4
  49 #undef R2
  50         };
  51         return table[byte];
  52     }
  53 }
  54
  55 namespace BitTorrent::LT
  56 {
  57     QBitArray toQBitArray(const lt::bitfield &bits)
  58     {
  59         const int STACK_ALLOC_SIZE = 10 * 1024;
  60
  61         const char *bitsData = bits.data();
  62         const int dataLength = (bits.size() + 7) / 8;
  63
  64         QVarLengthArray<char, STACK_ALLOC_SIZE> tmp(dataLength);
  65         for (int i = 0; i < dataLength; ++i)
  66             tmp[i] = reverseByte(bitsData[i]);
  67
  68         return QBitArray::fromBits(tmp.data(), bits.size());
  69     }
  70 }