libc/extlib.h

   1 /*
   2  *    Copyright (c) 2008 Joshua Phillips. All rights reserved.
   3  *
   4  *  Redistribution and use in source and binary forms, with or without
   5  *  modification, are permitted provided that the following conditions are
   6  *  met:
   7  *
   8  *    1. Redistributions of source code must retain the above copyright
   9  *       notice, this list of conditions and the following disclaimer.
  10  *    2. Redistributions in binary form must reproduce the above copyright
  11  *       notice, this list of conditions and the following disclaimer in
  12  *       the documentation and/or other materials provided with the
  13  *       distribution.
  14  *
  15  *  THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESS OR IMPLIED
  16  *  WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  17  *  OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  18  *  DISCLAIMED. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
  19  *  DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  20  *  DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
  21  *  GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  22  *  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
  23  *  IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
  24  *  OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
  25  *  IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  26  */
  27
  28 #ifndef _EXTLIB_H
  29 #define _EXTLIB_H
  30
  31 // return a/b rounded up
  32 static inline unsigned long uldivru(unsigned long a, unsigned long b)
  33 {
  34         unsigned long d;
  35         d = a / b;
  36         if (a % b)
  37                 d++;
  38         return d;
  39 }
  40
  41 static inline unsigned long long ulldivru(unsigned long long a, unsigned long long b)
  42 {
  43         unsigned long long d;
  44         d = a / b;
  45         if (a % b)
  46                 d++;
  47         return d;
  48 }
  49
  50 int log2ll(long long n); // return base-2 log of n, rounded down
  51
  52 // return log base 2 of v
  53 static inline unsigned int ilog2(unsigned int v)
  54 {
  55         static const unsigned int b[] = {0x2, 0xC, 0xF0, 0xFF00, 0xFFFF0000};
  56         static const unsigned int S[] = {1, 2, 4, 8, 16};
  57         int i;
  58         register unsigned int r = 0; // result goes here
  59         for (i=4; i>=0; i--){
  60                 if (v & b[i]){
  61                         v >>= S[i];
  62                         r |= S[i];
  63                 }
  64         }
  65         return r;
  66 }
  67
  68 // return log base 2 of v, rounded up
  69 static inline unsigned int ilog2up(unsigned int v)
  70 {
  71         // do it the nasty way
  72         unsigned int log = ilog2(v);
  73         if (v & ((1 << log) - 1))
  74                 log++;
  75         return log;
  76 }
  77
  78 // return 'value' rounded up to nearest 'alignment' multiple
  79 // hopefully, since these are inline, cc will optimize the division
  80 // and modulus for shifts and ands.
  81 static inline unsigned long alignup(unsigned long value, unsigned long alignment)
  82 {
  83         return uldivru(value, alignment) * alignment;
  84 }
  85
  86 // return 'value' rounded down to nearest 'alignment' multiple
  87 static inline unsigned long aligndn(unsigned long value, unsigned long alignment)
  88 {
  89         return (value / alignment) * alignment;
  90 }
  91
  92 static inline unsigned int bsf(unsigned int x)
  93 {
  94         unsigned int result;
  95         asm volatile (
  96           "bsfl %1,%0" : "=r" (result) : "r" (x));
  97         return result;
  98 }
  99
 100 #endif
 101