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 NS_round(double aNum) {
  22   return aNum >= 0.0 ? floor(aNum + 0.5) : ceil(aNum - 0.5);
  23 }
  24 inline float NS_roundf(float aNum) {
  25   return aNum >= 0.0f ? floorf(aNum + 0.5f) : ceilf(aNum - 0.5f);
  26 }
  27 inline int32_t NS_lround(double aNum) {
  28   return aNum >= 0.0 ? int32_t(aNum + 0.5) : int32_t(aNum - 0.5);
  29 }
  30
  31 /* NS_roundup30 rounds towards infinity for positive and       */
  32 /* negative numbers.                                           */
  33
  34 #if defined(XP_WIN) && defined(_M_IX86) && !defined(__GNUC__) && \
  35     !defined(__clang__)
  36 inline int32_t NS_lroundup30(float x) {
  37   /* Code derived from Laurent de Soras' paper at             */
  38   /* http://ldesoras.free.fr/doc/articles/rounding_en.pdf     */
  39
  40   /* Rounding up on Windows is expensive using the float to   */
  41   /* int conversion and the floor function. A faster          */
  42   /* approach is to use f87 rounding while assuming the       */
  43   /* default rounding mode of rounding to the nearest         */
  44   /* integer. This rounding mode, however, actually rounds    */
  45   /* to the nearest integer so we add the floating point      */
  46   /* number to itself and add our rounding factor before      */
  47   /* doing the conversion to an integer. We then do a right   */
  48   /* shift of one bit on the integer to divide by two.        */
  49
  50   /* This routine doesn't handle numbers larger in magnitude  */
  51   /* than 2^30 but this is fine for NSToCoordRound because    */
  52   /* Coords are limited to 2^30 in magnitude.                 */
  53
  54   static const double round_to_nearest = 0.5f;
  55   int i;
  56
  57   __asm {
  58     fld     x                   ; load fp argument
  59     fadd    st, st(0)           ; double it
  60     fadd    round_to_nearest    ; add the rounding factor
  61     fistp   dword ptr i         ; convert the result to int
  62   }
  63   return i >> 1; /* divide by 2 */
  64 }
  65 #endif /* XP_WIN && _M_IX86 && !__GNUC__ */
  66
  67 inline int32_t NS_lroundf(float aNum) {
  68   return aNum >= 0.0f ? int32_t(aNum + 0.5f) : int32_t(aNum - 0.5f);
  69 }
  70
  71 /*
  72  * hypot.  We don't need a super accurate version of this, if a platform
  73  * turns up with none of the possibilities below it would be okay to fall
  74  * back to sqrt(x*x + y*y).
  75  */
  76 inline double NS_hypot(double aNum1, double aNum2) {
  77 #ifdef __GNUC__
  78   return __builtin_hypot(aNum1, aNum2);
  79 #elif defined _WIN32
  80   return _hypot(aNum1, aNum2);
  81 #else
  82   return hypot(aNum1, aNum2);
  83 #endif
  84 }
  85
  86 /**
  87  * Check whether a floating point number is finite (not +/-infinity and not a
  88  * NaN value).
  89  */
  90 inline bool NS_finite(double aNum) {
  91 #ifdef WIN32
  92   // NOTE: '!!' casts an int to bool without spamming MSVC warning C4800.
  93   return !!_finite(aNum);
  94 #else
  95   return std::isfinite(aNum);
  96 #endif
  97 }
  98
  99 /**
 100  * Returns the result of the modulo of x by y using a floored division.
 101  * fmod(x, y) is using a truncated division.
 102  * The main difference is that the result of this method will have the sign of
 103  * y while the result of fmod(x, y) will have the sign of x.
 104  */
 105 inline double NS_floorModulo(double aNum1, double aNum2) {
 106   return (aNum1 - aNum2 * floor(aNum1 / aNum2));
 107 }
 108
 109 #endif