bitfield.h 3.8 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. #ifndef _D_BITFIELD_H_
  36. #define _D_BITFIELD_H_
  37. #include "common.h"
  38. #include <cassert>
  39. #include <cstdlib>
  40. #include "Util.h"
  41. namespace aria2 {
  42. namespace bitfield {
  43. // Returns the bit mask for the last byte. For example, nbits = 9,
  44. // then 0x80 is returned. nbits = 12, then 0xf0 is returned.
  45. inline unsigned char lastByteMask(size_t nbits)
  46. {
  47. return -256 >> (8-((nbits+7)/8*8-nbits));
  48. }
  49. // Returns true if index-th bits is set. Otherwise returns false.
  50. inline bool test(const unsigned char* bitfield, size_t nbits, size_t index)
  51. {
  52. assert(index < nbits);
  53. unsigned char mask = 128 >> (index%8);
  54. return (bitfield[index/8]&mask) != 0;
  55. }
  56. inline size_t countBit32(uint32_t n)
  57. {
  58. static const int nbits[] = {
  59. 0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4,
  60. 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
  61. 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
  62. 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
  63. 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
  64. 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
  65. 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
  66. 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
  67. 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
  68. 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
  69. 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
  70. 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
  71. 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
  72. 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
  73. 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
  74. 4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8,
  75. };
  76. return
  77. nbits[n&0xffu]+
  78. nbits[(n >> 8)&0xffu]+
  79. nbits[(n >> 16)&0xffu]+
  80. nbits[(n >> 24)&0xffu];
  81. }
  82. // Counts set bit in bitfield.
  83. inline size_t countSetBit(const unsigned char* bitfield, size_t nbits)
  84. {
  85. size_t count = 0;
  86. size_t size = sizeof(uint32_t);
  87. size_t len = (nbits+7)/8;
  88. size_t to = len/size;
  89. for(size_t i = 0; i < to; ++i) {
  90. count += countBit32(*reinterpret_cast<const uint32_t*>(&bitfield[i*size]));
  91. }
  92. for(size_t i = len-len%size; i < len-1; ++i) {
  93. count += countBit32(static_cast<uint32_t>(bitfield[i]));
  94. }
  95. if(nbits%32 != 0) {
  96. count +=
  97. countBit32(static_cast<uint32_t>(bitfield[len-1]&lastByteMask(nbits)));
  98. }
  99. return count;
  100. }
  101. } // namespace bitfield
  102. } // namespace aria2
  103. #endif // _D_BITFIELD_H_