src/util/bitscan.c

   1 /**************************************************************************
   2  *
   3  * Copyright 2008 VMware, Inc.
   4  * All Rights Reserved.
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a
   7  * copy of this software and associated documentation files (the
   8  * "Software"), to deal in the Software without restriction, including
   9  * without limitation the rights to use, copy, modify, merge, publish,
  10  * distribute, sub license, and/or sell copies of the Software, and to
  11  * permit persons to whom the Software is furnished to do so, subject to
  12  * the following conditions:
  13  *
  14  * The above copyright notice and this permission notice (including the
  15  * next paragraph) shall be included in all copies or substantial portions
  16  * of the Software.
  17  *
  18  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  19  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  20  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
  21  * IN NO EVENT SHALL VMWARE AND/OR ITS SUPPLIERS BE LIABLE FOR
  22  * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
  23  * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
  24  * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  25  *
  26  **************************************************************************/
  27
  28
  29 #include "bitscan.h"
  30
  31 #ifdef HAVE___BUILTIN_FFS
  32 #elif defined(_MSC_VER) && (_M_IX86 || _M_ARM || _M_AMD64 || _M_IA64)
  33 #else
  34 int
  35 ffs(unsigned i)
  36 {
  37    int bit = 0;
  38    if (!i)
  39       return bit;
  40    if (!(i & 0xffff)) {
  41       bit += 16;
  42       i >>= 16;
  43    }
  44    if (!(i & 0xff)) {
  45       bit += 8;
  46       i >>= 8;
  47    }
  48    if (!(i & 0xf)) {
  49       bit += 4;
  50       i >>= 4;
  51    }
  52    if (!(i & 0x3)) {
  53       bit += 2;
  54       i >>= 2;
  55    }
  56    if (!(i & 0x1))
  57       bit += 1;
  58    return bit + 1;
  59 }
  60 #endif
  61
  62 #ifdef HAVE___BUILTIN_FFSLL
  63 #elif defined(_MSC_VER) && (_M_AMD64 || _M_ARM || _M_IA64)
  64 #else
  65 int
  66 ffsll(uint64_t val)
  67 {
  68    int bit;
  69
  70    bit = ffs((unsigned) (val & 0xffffffff));
  71    if (bit != 0)
  72       return bit;
  73
  74    bit = ffs((unsigned) (val >> 32));
  75    if (bit != 0)
  76       return 32 + bit;
  77
  78    return 0;
  79 }
  80 #endif