xpcom/ds/nsMathUtils.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef nsMathUtils_h__
   8 #define nsMathUtils_h__
   9
  10 #include "nscore.h"
  11 #include <cmath>
  12 #include <float.h>
  13
  14 #if defined(XP_SOLARIS)
  15 #include <ieeefp.h>
  16 #endif
  17
  18 /*
  19  * round
  20  */
  21 inline double
  22 NS_round(double aNum)
  23 {
  24   return aNum >= 0.0 ? floor(aNum + 0.5) : ceil(aNum - 0.5);
  25 }
  26 inline float
  27 NS_roundf(float aNum)
  28 {
  29   return aNum >= 0.0f ? floorf(aNum + 0.5f) : ceilf(aNum - 0.5f);
  30 }
  31 inline int32_t
  32 NS_lround(double aNum)
  33 {
  34   return aNum >= 0.0 ? int32_t(aNum + 0.5) : int32_t(aNum - 0.5);
  35 }
  36
  37 /* NS_roundup30 rounds towards infinity for positive and       */
  38 /* negative numbers.                                           */
  39
  40 #if defined(XP_WIN32) && defined(_M_IX86) && !defined(__GNUC__) && !defined(__clang__)
  41 inline int32_t NS_lroundup30(float x)
  42 {
  43   /* Code derived from Laurent de Soras' paper at             */
  44   /* http://ldesoras.free.fr/doc/articles/rounding_en.pdf     */
  45
  46   /* Rounding up on Windows is expensive using the float to   */
  47   /* int conversion and the floor function. A faster          */
  48   /* approach is to use f87 rounding while assuming the       */
  49   /* default rounding mode of rounding to the nearest         */
  50   /* integer. This rounding mode, however, actually rounds    */
  51   /* to the nearest integer so we add the floating point      */
  52   /* number to itself and add our rounding factor before      */
  53   /* doing the conversion to an integer. We then do a right   */
  54   /* shift of one bit on the integer to divide by two.        */
  55
  56   /* This routine doesn't handle numbers larger in magnitude  */
  57   /* than 2^30 but this is fine for NSToCoordRound because    */
  58   /* Coords are limited to 2^30 in magnitude.                 */
  59
  60   static const double round_to_nearest = 0.5f;
  61   int i;
  62
  63   __asm {
  64     fld     x                   ; load fp argument
  65     fadd    st, st(0)           ; double it
  66     fadd    round_to_nearest    ; add the rounding factor
  67     fistp   dword ptr i         ; convert the result to int
  68   }
  69   return i >> 1;                /* divide by 2 */
  70 }
  71 #endif /* XP_WIN32 && _M_IX86 && !__GNUC__ */
  72
  73 inline int32_t
  74 NS_lroundf(float aNum)
  75 {
  76   return aNum >= 0.0f ? int32_t(aNum + 0.5f) : int32_t(aNum - 0.5f);
  77 }
  78
  79 /*
  80  * hypot.  We don't need a super accurate version of this, if a platform
  81  * turns up with none of the possibilities below it would be okay to fall
  82  * back to sqrt(x*x + y*y).
  83  */
  84 inline double
  85 NS_hypot(double aNum1, double aNum2)
  86 {
  87 #ifdef __GNUC__
  88   return __builtin_hypot(aNum1, aNum2);
  89 #elif defined _WIN32
  90   return _hypot(aNum1, aNum2);
  91 #else
  92   return hypot(aNum1, aNum2);
  93 #endif
  94 }
  95
  96 /**
  97  * Check whether a floating point number is finite (not +/-infinity and not a
  98  * NaN value).
  99  */
 100 inline bool
 101 NS_finite(double aNum)
 102 {
 103 #ifdef WIN32
 104   // NOTE: '!!' casts an int to bool without spamming MSVC warning C4800.
 105   return !!_finite(aNum);
 106 #else
 107   return std::isfinite(aNum);
 108 #endif
 109 }
 110
 111 /**
 112  * Returns the result of the modulo of x by y using a floored division.
 113  * fmod(x, y) is using a truncated division.
 114  * The main difference is that the result of this method will have the sign of
 115  * y while the result of fmod(x, y) will have the sign of x.
 116  */
 117 inline double
 118 NS_floorModulo(double aNum1, double aNum2)
 119 {
 120   return (aNum1 - aNum2 * floor(aNum1 / aNum2));
 121 }
 122
 123 #endif