LongestSequencePieceSelector.cc 2.9 KB

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  1. /* <!-- copyright */
  2. /*
  3. * aria2 - The high speed download utility
  4. *
  5. * Copyright (C) 2009 Tatsuhiro Tsujikawa
  6. *
  7. * This program is free software; you can redistribute it and/or modify
  8. * it under the terms of the GNU General Public License as published by
  9. * the Free Software Foundation; either version 2 of the License, or
  10. * (at your option) any later version.
  11. *
  12. * This program is distributed in the hope that it will be useful,
  13. * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14. * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  15. * GNU General Public License for more details.
  16. *
  17. * You should have received a copy of the GNU General Public License
  18. * along with this program; if not, write to the Free Software
  19. * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20. *
  21. * In addition, as a special exception, the copyright holders give
  22. * permission to link the code of portions of this program with the
  23. * OpenSSL library under certain conditions as described in each
  24. * individual source file, and distribute linked combinations
  25. * including the two.
  26. * You must obey the GNU General Public License in all respects
  27. * for all of the code used other than OpenSSL. If you modify
  28. * file(s) with this exception, you may extend this exception to your
  29. * version of the file(s), but you are not obligated to do so. If you
  30. * do not wish to do so, delete this exception statement from your
  31. * version. If you delete this exception statement from all source
  32. * files in the program, then also delete it here.
  33. */
  34. /* copyright --> */
  35. #include "LongestSequencePieceSelector.h"
  36. #include "bitfield.h"
  37. namespace aria2 {
  38. namespace {
  39. size_t getStartIndex(size_t from, const unsigned char* bitfield, size_t nbits)
  40. {
  41. while (from < nbits && !bitfield::test(bitfield, nbits, from)) {
  42. ++from;
  43. }
  44. if (nbits <= from) {
  45. return nbits;
  46. }
  47. else {
  48. return from;
  49. }
  50. }
  51. } // namespace
  52. namespace {
  53. size_t getEndIndex(size_t from, const unsigned char* bitfield, size_t nbits)
  54. {
  55. while (from < nbits && bitfield::test(bitfield, nbits, from)) {
  56. ++from;
  57. }
  58. return from;
  59. }
  60. } // namespace
  61. bool LongestSequencePieceSelector::select(size_t& index,
  62. const unsigned char* bitfield,
  63. size_t nbits) const
  64. {
  65. size_t mstartindex = 0;
  66. size_t mendindex = 0;
  67. size_t nextIndex = 0;
  68. while (nextIndex < nbits) {
  69. size_t startindex = getStartIndex(nextIndex, bitfield, nbits);
  70. if (startindex == nbits) {
  71. break;
  72. }
  73. size_t endindex = getEndIndex(startindex, bitfield, nbits);
  74. if (mendindex - mstartindex < endindex - startindex) {
  75. mstartindex = startindex;
  76. mendindex = endindex;
  77. }
  78. nextIndex = endindex;
  79. }
  80. if (mendindex - mstartindex > 0) {
  81. index = mendindex - 1;
  82. return true;
  83. }
  84. else {
  85. return false;
  86. }
  87. }
  88. } // namespace aria2