hphp/util/bits.h

   1 /*
   2    +----------------------------------------------------------------------+
   3    | HipHop for PHP                                                       |
   4    +----------------------------------------------------------------------+
   5    | Copyright (c) 2010-present Facebook, Inc. (http://www.facebook.com)  |
   6    +----------------------------------------------------------------------+
   7    | This source file is subject to version 3.01 of the PHP license,      |
   8    | that is bundled with this package in the file LICENSE, and is        |
   9    | available through the world-wide-web at the following url:           |
  10    | http://www.php.net/license/3_01.txt                                  |
  11    | If you did not receive a copy of the PHP license and are unable to   |
  12    | obtain it through the world-wide-web, please send a note to          |
  13    | license@php.net so we can mail you a copy immediately.               |
  14    +----------------------------------------------------------------------+
  15 */
  16
  17 #ifndef incl_HPHP_BITS_H_
  18 #define incl_HPHP_BITS_H_
  19
  20 namespace HPHP {
  21 ///////////////////////////////////////////////////////////////////////////////
  22
  23 template <typename T>
  24 struct BitInfo {
  25   static const T NumBits  = sizeof(T) * 8;
  26   static const T HighMask = 0x1 << (NumBits - 1);
  27 };
  28
  29 template <unsigned int i, unsigned int m>
  30 struct BitCountImpl {
  31   enum { value = ((i & m) ? 1 : 0) + BitCountImpl< i, (m >> 1) >::value };
  32 };
  33
  34 template <unsigned int i>
  35 struct BitCountImpl<i, 0> {
  36   enum { value = 0 };
  37 };
  38
  39 template <unsigned int i>
  40 struct BitCount: public BitCountImpl<i,
  41                                      BitInfo<unsigned int>::HighMask>
  42 {};
  43
  44 template <unsigned int i, bool p, unsigned int m>
  45 struct BitPhaseImpl {
  46   enum {
  47     value = ((i & m) ? (p ? 0 : 1) : (p ? 1 : 0)) +
  48             BitPhaseImpl<i, ((i & m) != 0), (m >> 1)>::value
  49   };
  50 };
  51
  52 template <unsigned int i, bool p>
  53 struct BitPhaseImpl<i, p, 0> {
  54   enum { value = 0 };
  55 };
  56
  57 template <unsigned int i>
  58 struct BitPhase : public BitPhaseImpl<i,
  59                                       i & BitInfo<unsigned int>::HighMask,
  60                                       BitInfo<unsigned int>::HighMask>
  61 {};
  62
  63 ///////////////////////////////////////////////////////////////////////////////
  64 }
  65
  66 #endif // incl_HPHP_BITS_H_