xpcom/ds/nsMathUtils.h

   1 /* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 4 -*-
   2  * This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this
   4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   5
   6 #ifndef nsMathUtils_h__
   7 #define nsMathUtils_h__
   8
   9 #define _USE_MATH_DEFINES /* needed for M_ constants on Win32 */
  10
  11 #include "nscore.h"
  12 #include <cmath>
  13 #include <float.h>
  14
  15 #ifdef SOLARIS
  16 #include <ieeefp.h>
  17 #endif
  18
  19 /*
  20  * round
  21  */
  22 inline double
  23 NS_round(double aNum)
  24 {
  25   return aNum >= 0.0 ? floor(aNum + 0.5) : ceil(aNum - 0.5);
  26 }
  27 inline float
  28 NS_roundf(float aNum)
  29 {
  30   return aNum >= 0.0f ? floorf(aNum + 0.5f) : ceilf(aNum - 0.5f);
  31 }
  32 inline int32_t
  33 NS_lround(double aNum)
  34 {
  35   return aNum >= 0.0 ? int32_t(aNum + 0.5) : int32_t(aNum - 0.5);
  36 }
  37
  38 /* NS_roundup30 rounds towards infinity for positive and       */
  39 /* negative numbers.                                           */
  40
  41 #if defined(XP_WIN32) && defined(_M_IX86) && !defined(__GNUC__) && !defined(__clang__)
  42 inline int32_t NS_lroundup30(float x)
  43 {
  44   /* Code derived from Laurent de Soras' paper at             */
  45   /* http://ldesoras.free.fr/doc/articles/rounding_en.pdf     */
  46
  47   /* Rounding up on Windows is expensive using the float to   */
  48   /* int conversion and the floor function. A faster          */
  49   /* approach is to use f87 rounding while assuming the       */
  50   /* default rounding mode of rounding to the nearest         */
  51   /* integer. This rounding mode, however, actually rounds    */
  52   /* to the nearest integer so we add the floating point      */
  53   /* number to itself and add our rounding factor before      */
  54   /* doing the conversion to an integer. We then do a right   */
  55   /* shift of one bit on the integer to divide by two.        */
  56
  57   /* This routine doesn't handle numbers larger in magnitude  */
  58   /* than 2^30 but this is fine for NSToCoordRound because    */
  59   /* Coords are limited to 2^30 in magnitude.                 */
  60
  61   static const double round_to_nearest = 0.5f;
  62   int i;
  63
  64   __asm {
  65     fld     x                   ; load fp argument
  66     fadd    st, st(0)           ; double it
  67     fadd    round_to_nearest    ; add the rounding factor
  68     fistp   dword ptr i         ; convert the result to int
  69   }
  70   return i >> 1;                /* divide by 2 */
  71 }
  72 #endif /* XP_WIN32 && _M_IX86 && !__GNUC__ */
  73
  74 inline int32_t
  75 NS_lroundf(float aNum)
  76 {
  77   return aNum >= 0.0f ? int32_t(aNum + 0.5f) : int32_t(aNum - 0.5f);
  78 }
  79
  80 /*
  81  * hypot.  We don't need a super accurate version of this, if a platform
  82  * turns up with none of the possibilities below it would be okay to fall
  83  * back to sqrt(x*x + y*y).
  84  */
  85 inline double
  86 NS_hypot(double aNum1, double aNum2)
  87 {
  88 #ifdef __GNUC__
  89   return __builtin_hypot(aNum1, aNum2);
  90 #elif defined _WIN32
  91   return _hypot(aNum1, aNum2);
  92 #else
  93   return hypot(aNum1, aNum2);
  94 #endif
  95 }
  96
  97 /**
  98  * Check whether a floating point number is finite (not +/-infinity and not a
  99  * NaN value).
 100  */
 101 inline bool
 102 NS_finite(double aNum)
 103 {
 104 #ifdef WIN32
 105   // NOTE: '!!' casts an int to bool without spamming MSVC warning C4800.
 106   return !!_finite(aNum);
 107 #elif defined(XP_DARWIN)
 108   // Darwin has deprecated |finite| and recommends |isfinite|. The former is
 109   // not present in the iOS SDK.
 110   return std::isfinite(aNum);
 111 #else
 112   return finite(aNum);
 113 #endif
 114 }
 115
 116 /**
 117  * Returns the result of the modulo of x by y using a floored division.
 118  * fmod(x, y) is using a truncated division.
 119  * The main difference is that the result of this method will have the sign of
 120  * y while the result of fmod(x, y) will have the sign of x.
 121  */
 122 inline double
 123 NS_floorModulo(double aNum1, double aNum2)
 124 {
 125   return (aNum1 - aNum2 * floor(aNum1 / aNum2));
 126 }
 127
 128 #endif