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1 | #ifndef __XCB_BITOPS_H__ |
---|---|

2 | #define __XCB_BITOPS_H__ |

3 | |

4 | /* Copyright (C) 2007 Bart Massey |

5 | * |

6 | * Permission is hereby granted, free of charge, to any person obtaining a |

7 | * copy of this software and associated documentation files (the "Software"), |

8 | * to deal in the Software without restriction, including without limitation |

9 | * the rights to use, copy, modify, merge, publish, distribute, sublicense, |

10 | * and/or sell copies of the Software, and to permit persons to whom the |

11 | * Software is furnished to do so, subject to the following conditions: |

12 | * |

13 | * The above copyright notice and this permission notice shall be included in |

14 | * all copies or substantial portions of the Software. |

15 | * |

16 | * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |

17 | * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |

18 | * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE |

19 | * AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN |

20 | * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN |

21 | * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. |

22 | * |

23 | * Except as contained in this notice, the names of the authors or their |

24 | * institutions shall not be used in advertising or otherwise to promote the |

25 | * sale, use or other dealings in this Software without prior written |

26 | * authorization from the authors. |

27 | */ |

28 | |

29 | #include <assert.h> |

30 | #include <inttypes.h> |

31 | #include <X11/Xfuncproto.h> |

32 | |

33 | /** |

34 | * @defgroup xcb__bitops XCB Bit Operations |

35 | * |

36 | * Inline functions for common bit ops used in XCB and elsewhere. |

37 | * |

38 | * @{ |

39 | */ |

40 | |

41 | |

42 | /** |

43 | * Create a low-order bitmask. |

44 | * @param n Mask size. |

45 | * @return Mask. |

46 | * |

47 | * Create a bitmask with the lower @p n bits set and the |

48 | * rest of the word clear. |

49 | * @ingroup xcb__bitops |

50 | */ |

51 | _X_INLINE static uint32_t |

52 | xcb_mask(uint32_t n) |

53 | { |

54 | return n == 32 ? ~0 : (1 << n) - 1; |

55 | } |

56 | |

57 | |

58 | /** |

59 | * Population count. |

60 | * @param n Integer representing a bitset. |

61 | * @return Number of 1 bits in the bitset. |

62 | * |

63 | * This is a reasonably fast algorithm for counting the bits |

64 | * in a 32-bit word. Currently a classic binary |

65 | * divide-and-conquer popcount: popcount_2() from |

66 | * http://en.wikipedia.org/wiki/Hamming_weight. |

67 | * @ingroup xcb__bitops |

68 | */ |

69 | |

70 | |

71 | /* 15 ops, 3 long immediates, 14 stages, 9 alu ops, 9 alu stages */ |

72 | _X_INLINE static uint32_t |

73 | xcb_popcount(uint32_t x) |

74 | { |

75 | uint32_t m1 = 0x55555555; |

76 | uint32_t m2 = 0x33333333; |

77 | uint32_t m4 = 0x0f0f0f0f; |

78 | x -= (x >> 1) & m1; |

79 | x = (x & m2) + ((x >> 2) & m2); |

80 | x = (x + (x >> 4)) & m4; |

81 | x += x >> 8; |

82 | return (x + (x >> 16)) & 0x3f; |

83 | } |

84 | |

85 | |

86 | /** |

87 | * Round up to the next power-of-two unit size. |

88 | * @param base Number to be rounded up. |

89 | * @param pad Multiple to be rounded to; must be a power of two. |

90 | * @return Rounded-up number. |

91 | * |

92 | * Rounds @p base up to a multiple of @p pad, where @p pad |

93 | * is a power of two. The more general case is handled by |

94 | * xcb_roundup(). |

95 | * @ingroup xcb__bitops |

96 | */ |

97 | _X_INLINE static uint32_t |

98 | xcb_roundup_2 (uint32_t base, uint32_t pad) |

99 | { |

100 | return (base + pad - 1) & -pad; |

101 | } |

102 | |

103 | /** |

104 | * Round down to the next power-of-two unit size. |

105 | * @param base Number to be rounded down. |

106 | * @param pad Multiple to be rounded to; must be a power of two. |

107 | * @return Rounded-down number. |

108 | * |

109 | * Rounds @p base down to a multiple of @p pad, where @p pad |

110 | * is a power of two. The more general case is handled by |

111 | * xcb_rounddown(). |

112 | * @ingroup xcb__bitops |

113 | */ |

114 | _X_INLINE static uint32_t |

115 | xcb_rounddown_2 (uint32_t base, uint32_t pad) |

116 | { |

117 | return base & -pad; |

118 | } |

119 | |

120 | /** |

121 | * Round up to the next unit size. |

122 | * @param base Number to be rounded up. |

123 | * @param pad Multiple to be rounded to. |

124 | * @return Rounded-up number. |

125 | * |

126 | * This is a general routine for rounding @p base up |

127 | * to a multiple of @p pad. If you know that @p pad |

128 | * is a power of two, you should probably call xcb_roundup_2() |

129 | * instead. |

130 | * @ingroup xcb__bitops |

131 | */ |

132 | _X_INLINE static uint32_t |

133 | xcb_roundup (uint32_t base, uint32_t pad) |

134 | { |

135 | uint32_t b = base + pad - 1; |

136 | /* faster if pad is a power of two */ |

137 | if (((pad - 1) & pad) == 0) |

138 | return b & -pad; |

139 | return b - b % pad; |

140 | } |

141 | |

142 | |

143 | /** |

144 | * Round down to the next unit size. |

145 | * @param base Number to be rounded down. |

146 | * @param pad Multiple to be rounded to. |

147 | * @return Rounded-down number. |

148 | * |

149 | * This is a general routine for rounding @p base down |

150 | * to a multiple of @p pad. If you know that @p pad |

151 | * is a power of two, you should probably call xcb_rounddown_2() |

152 | * instead. |

153 | * @ingroup xcb__bitops |

154 | */ |

155 | _X_INLINE static uint32_t |

156 | xcb_rounddown (uint32_t base, uint32_t pad) |

157 | { |

158 | /* faster if pad is a power of two */ |

159 | if (((pad - 1) & pad) == 0) |

160 | return base & -pad; |

161 | return base - base % pad; |

162 | } |

163 | |

164 | |

165 | /** |

166 | * Reverse bits of word. |

167 | * @param x Target word. |

168 | * @param n Number of low-order bits to reverse. |

169 | * @return Word with low @p n bits reversed, all others 0. |

170 | * |

171 | * Reverses the bottom @p n bits of @p x. |

172 | * @ingroup xcb__bitops |

173 | */ |

174 | _X_INLINE static uint32_t |

175 | xcb_bit_reverse(uint32_t x, uint8_t n) { |

176 | uint32_t m1 = 0x00ff00ff; |

177 | uint32_t m2 = 0x0f0f0f0f; |

178 | uint32_t m3 = 0x33333333; |

179 | uint32_t m4 = 0x55555555; |

180 | x = ((x << 16) | (x >> 16)); |

181 | x = ((x & m1) << 8) | ((x >> 8) & m1); |

182 | x = ((x & m2) << 4) | ((x >> 4) & m2); |

183 | x = ((x & m3) << 2) | ((x >> 2) & m3); |

184 | x = ((x & m4) << 1) | ((x >> 1) & m4); |

185 | x >>= 32 - n; |

186 | return x; |

187 | } |

188 | |

189 | |

190 | /** |

191 | * Host byte order. |

192 | * @return The byte order of the host. |

193 | * |

194 | * Tests the host's byte order and returns either |

195 | * XCB_IMAGE_ORDER_MSB_FIRST or XCB_IMAGE_ORDER_LSB_FIRST |

196 | * as appropriate. |

197 | * @ingroup xcb__bitops |

198 | */ |

199 | _X_INLINE static xcb_image_order_t |

200 | xcb_host_byte_order(void) { |

201 | uint32_t endian_test = 0x01020304; |

202 | |

203 | switch (*(char *)&endian_test) { |

204 | case 0x01: |

205 | return XCB_IMAGE_ORDER_MSB_FIRST; |

206 | case 0x04: |

207 | return XCB_IMAGE_ORDER_LSB_FIRST; |

208 | } |

209 | assert(0); |

210 | } |

211 | |

212 | #endif /* __XCB_BITOPS_H__ */ |

213 |

Warning: That file was not part of the compilation database. It may have many parsing errors.