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 #pragma once
  18
  19 namespace HPHP {
  20 ///////////////////////////////////////////////////////////////////////////////
  21
  22 template <typename T>
  23 struct BitInfo {
  24   static const T NumBits  = sizeof(T) * 8;
  25   static const T HighMask = 0x1 << (NumBits - 1);
  26 };
  27
  28 template <unsigned int i, unsigned int m>
  29 struct BitCountImpl {
  30   enum { value = ((i & m) ? 1 : 0) + BitCountImpl< i, (m >> 1) >::value };
  31 };
  32
  33 template <unsigned int i>
  34 struct BitCountImpl<i, 0> {
  35   enum { value = 0 };
  36 };
  37
  38 template <unsigned int i>
  39 struct BitCount: public BitCountImpl<i,
  40                                      BitInfo<unsigned int>::HighMask>
  41 {};
  42
  43 template <unsigned int i, bool p, unsigned int m>
  44 struct BitPhaseImpl {
  45   enum {
  46     value = ((i & m) ? (p ? 0 : 1) : (p ? 1 : 0)) +
  47             BitPhaseImpl<i, ((i & m) != 0), (m >> 1)>::value
  48   };
  49 };
  50
  51 template <unsigned int i, bool p>
  52 struct BitPhaseImpl<i, p, 0> {
  53   enum { value = 0 };
  54 };
  55
  56 template <unsigned int i>
  57 struct BitPhase : public BitPhaseImpl<i,
  58                                       i & BitInfo<unsigned int>::HighMask,
  59                                       BitInfo<unsigned int>::HighMask>
  60 {};
  61
  62 ///////////////////////////////////////////////////////////////////////////////
  63 }
  64