src/base/intmath.hh

   1 /*
   2  * Copyright (c) 2001, 2003-2005 The Regents of The University of Michigan
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions are
   7  * met: redistributions of source code must retain the above copyright
   8  * notice, this list of conditions and the following disclaimer;
   9  * redistributions in binary form must reproduce the above copyright
  10  * notice, this list of conditions and the following disclaimer in the
  11  * documentation and/or other materials provided with the distribution;
  12  * neither the name of the copyright holders nor the names of its
  13  * contributors may be used to endorse or promote products derived from
  14  * this software without specific prior written permission.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  17  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  18  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  19  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  20  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  21  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  22  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  26  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27  */
  28
  29 #ifndef __BASE_INTMATH_HH__
  30 #define __BASE_INTMATH_HH__
  31
  32 #include <cassert>
  33
  34 #include "base/logging.hh"
  35 #include "base/types.hh"
  36
  37 inline uint64_t
  38 power(uint32_t n, uint32_t e)
  39 {
  40     if (e > 20)
  41         warn("Warning, power() function is quite slow for large exponents\n");
  42
  43     if (e == 0)
  44         return 1;
  45
  46     uint64_t result = n;
  47     uint64_t old_result = 0;
  48     for (int x = 1; x < e; x++) {
  49         old_result = result;
  50         result *= n;
  51         if (old_result > result)
  52             warn("power() overflowed!\n");
  53     }
  54     return result;
  55 }
  56
  57
  58 inline int
  59 floorLog2(unsigned x)
  60 {
  61     assert(x > 0);
  62
  63     int y = 0;
  64
  65     if (x & 0xffff0000) { y += 16; x >>= 16; }
  66     if (x & 0x0000ff00) { y +=  8; x >>=  8; }
  67     if (x & 0x000000f0) { y +=  4; x >>=  4; }
  68     if (x & 0x0000000c) { y +=  2; x >>=  2; }
  69     if (x & 0x00000002) { y +=  1; }
  70
  71     return y;
  72 }
  73
  74 inline int
  75 floorLog2(unsigned long x)
  76 {
  77     assert(x > 0);
  78
  79     int y = 0;
  80
  81 #if defined(__LP64__)
  82     if (x & ULL(0xffffffff00000000)) { y += 32; x >>= 32; }
  83 #endif
  84     if (x & 0xffff0000) { y += 16; x >>= 16; }
  85     if (x & 0x0000ff00) { y +=  8; x >>=  8; }
  86     if (x & 0x000000f0) { y +=  4; x >>=  4; }
  87     if (x & 0x0000000c) { y +=  2; x >>=  2; }
  88     if (x & 0x00000002) { y +=  1; }
  89
  90     return y;
  91 }
  92
  93 inline int
  94 floorLog2(unsigned long long x)
  95 {
  96     assert(x > 0);
  97
  98     int y = 0;
  99
 100     if (x & ULL(0xffffffff00000000)) { y += 32; x >>= 32; }
 101     if (x & ULL(0x00000000ffff0000)) { y += 16; x >>= 16; }
 102     if (x & ULL(0x000000000000ff00)) { y +=  8; x >>=  8; }
 103     if (x & ULL(0x00000000000000f0)) { y +=  4; x >>=  4; }
 104     if (x & ULL(0x000000000000000c)) { y +=  2; x >>=  2; }
 105     if (x & ULL(0x0000000000000002)) { y +=  1; }
 106
 107     return y;
 108 }
 109
 110 inline int
 111 floorLog2(int x)
 112 {
 113     assert(x > 0);
 114     return floorLog2((unsigned)x);
 115 }
 116
 117 inline int
 118 floorLog2(long x)
 119 {
 120     assert(x > 0);
 121     return floorLog2((unsigned long)x);
 122 }
 123
 124 inline int
 125 floorLog2(long long x)
 126 {
 127     assert(x > 0);
 128     return floorLog2((unsigned long long)x);
 129 }
 130
 131 template <class T>
 132 inline int
 133 ceilLog2(const T& n)
 134 {
 135     assert(n > 0);
 136     if (n == 1)
 137         return 0;
 138
 139     return floorLog2(n - (T)1) + 1;
 140 }
 141
 142 template <class T>
 143 inline bool
 144 isPowerOf2(const T& n)
 145 {
 146     return n != 0 && floorLog2(n) == ceilLog2(n);
 147 }
 148
 149 template <class T, class U>
 150 inline T
 151 divCeil(const T& a, const U& b)
 152 {
 153     return (a + b - 1) / b;
 154 }
 155
 156 /**
 157  * This function is used to align addresses in memory.
 158  *
 159  * @param val is the address to be aligned.
 160  * @param align is the alignment. Can only be a power of 2.
 161  * @return The aligned address. The smallest number divisible
 162  * by @param align which is greater than or equal to @param val.
 163 */
 164 template <class T, class U>
 165 inline T
 166 roundUp(const T& val, const U& align)
 167 {
 168     assert(isPowerOf2(align));
 169     T mask = (T)align - 1;
 170     return (val + mask) & ~mask;
 171 }
 172
 173 /**
 174  * This function is used to align addresses in memory.
 175  *
 176  * @param val is the address to be aligned.
 177  * @param align is the alignment. Can only be a power of 2.
 178  * @return The aligned address. The biggest number divisible
 179  * by @param align which is less than or equal to @param val.
 180 */
 181 template <class T, class U>
 182 inline T
 183 roundDown(const T& val, const U& align)
 184 {
 185     assert(isPowerOf2(align));
 186     T mask = (T)align - 1;
 187     return val & ~mask;
 188 }
 189
 190 #endif // __BASE_INTMATH_HH__