src/thirdparty/VirtualDub/system/source/bitmath.cpp

   1 //      VirtualDub - Video processing and capture application
   2 //      System library component
   3 //      Copyright (C) 1998-2007 Avery Lee, All Rights Reserved.
   4 //
   5 //      Beginning with 1.6.0, the VirtualDub system library is licensed
   6 //      differently than the remainder of VirtualDub.  This particular file is
   7 //      thus licensed as follows (the "zlib" license):
   8 //
   9 //      This software is provided 'as-is', without any express or implied
  10 //      warranty.  In no event will the authors be held liable for any
  11 //      damages arising from the use of this software.
  12 //
  13 //      Permission is granted to anyone to use this software for any purpose,
  14 //      including commercial applications, and to alter it and redistribute it
  15 //      freely, subject to the following restrictions:
  16 //
  17 //      1.      The origin of this software must not be misrepresented; you must
  18 //              not claim that you wrote the original software. If you use this
  19 //              software in a product, an acknowledgment in the product
  20 //              documentation would be appreciated but is not required.
  21 //      2.      Altered source versions must be plainly marked as such, and must
  22 //              not be misrepresented as being the original software.
  23 //      3.      This notice may not be removed or altered from any source
  24 //              distribution.
  25
  26 #include "stdafx.h"
  27 #include <vd2/system/bitmath.h>
  28
  29 int VDCountBits(uint32 v) {
  30         v -= (v >> 1) & 0x55555555;
  31         v = ((v & 0xcccccccc) >> 2) + (v & 0x33333333);
  32         v = (v + (v >> 4)) & 0x0f0f0f0f;
  33         return (v * 0x01010101) >> 24;
  34 }
  35
  36 #ifndef VD_COMPILER_MSVC_VC8
  37
  38         int VDFindLowestSetBit(uint32 v) {
  39                 for(int i=0; i<32; ++i) {
  40                         if (v & 1)
  41                                 return i;
  42                         v >>= 1;
  43                 }
  44
  45                 return 32;
  46         }
  47
  48         int VDFindHighestSetBit(uint32 v) {
  49                 for(int i=31; i>=0; --i) {
  50                         if ((sint32)v < 0)
  51                                 return i;
  52                         v += v;
  53                 }
  54                 return -1;
  55         }
  56
  57 #endif
  58
  59 uint32 VDCeilToPow2(uint32 v) {
  60         v += v;
  61         --v;
  62
  63         while(uint32 x = v & (v - 1))
  64                 v = x;
  65
  66         return v;
  67 }