| 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__ */ |