hphp/util/tribool.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 #pragma once
  17
  18 #include <cstdint>
  19
  20 namespace HPHP {
  21
  22 //////////////////////////////////////////////////////////////////////
  23
  24 /*
  25  * Represents definitely yes, definitely no, or maybe.
  26  */
  27
  28 enum class TriBool : uint8_t {
  29   Yes   = (1 << 0),
  30   No    = (1 << 1),
  31   Maybe = Yes | No
  32 };
  33
  34 // Union represents "either", so values become Maybe unless both
  35 // agree. The bit values of yes and no have been chosen to make this
  36 // efficient.
  37 inline TriBool operator|(TriBool a, TriBool b) {
  38   return static_cast<TriBool>(
  39     static_cast<std::underlying_type<TriBool>::type>(a) |
  40     static_cast<std::underlying_type<TriBool>::type>(b)
  41   );
  42 }
  43
  44 // Intersection represents sequentiality, so Yes wins over everything,
  45 // and No yields to anything else.
  46 inline TriBool operator&(TriBool a, TriBool b) {
  47   if (a == TriBool::No) return b;
  48   if (a == TriBool::Yes) return a;
  49   if (b == TriBool::Yes) return b;
  50   return a;
  51 }
  52
  53 inline TriBool& operator|=(TriBool& a, TriBool b) {
  54   a = a | b;
  55   return a;
  56 }
  57
  58 inline TriBool& operator&=(TriBool& a, TriBool b) {
  59   a = a & b;
  60   return a;
  61 }
  62
  63 inline TriBool yesOrNo(bool b) { return b ? TriBool::Yes : TriBool::No; }
  64 inline TriBool yesOrMaybe(bool b) { return b ? TriBool::Yes : TriBool::Maybe; }
  65 inline TriBool maybeOrNo(bool b) { return b ? TriBool::Maybe : TriBool::No; }
  66 inline TriBool noOrMaybe(bool b) { return b ? TriBool::No : TriBool::Maybe; }
  67
  68 inline const char* show(TriBool b) {
  69   if (b == TriBool::Yes) return "yes";
  70   if (b == TriBool::No) return "no";
  71   return "maybe";
  72 }
  73
  74 //////////////////////////////////////////////////////////////////////
  75
  76 }