gecko-dev/xpcom/ds/nsMathUtils.h

/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 4 -*-
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 * for the specific language governing rights and limitations under the
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 * The Original Code is Mozilla Foundation code.
 *
 * The Initial Developer of the Original Code is Mozilla Foundation.
 * Portions created by the Initial Developer are Copyright (C) 2007
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 * Contributor(s):
 *   Stuart Parmenter <stuart@mozilla.com>
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#ifndef nsMathUtils_h__
#define nsMathUtils_h__

#define _USE_MATH_DEFINES /* needed for M_ constants on Win32 */

#include "nscore.h"
#include <math.h>
#include <float.h>

/*
 * The M_ constants are not defined by the WinCE/WinMo SDKs even with
 * _USE_MATH_DEFINES.  Provide a fallback.  We assume that the entire
 * set is not available if M_E isn't.  Values taken from GNU libc,
 * providing just enough precision for IEEE double.
 */

#ifndef M_E
# define M_E            2.7182818284590452354   /* e */
# define M_LOG2E        1.4426950408889634074   /* log_2 e */
# define M_LOG10E       0.43429448190325182765  /* log_10 e */
# define M_LN2          0.69314718055994530942  /* log_e 2 */
# define M_LN10         2.30258509299404568402  /* log_e 10 */
# define M_PI           3.14159265358979323846  /* pi */
# define M_PI_2         1.57079632679489661923  /* pi/2 */
# define M_PI_4         0.78539816339744830962  /* pi/4 */
# define M_1_PI         0.31830988618379067154  /* 1/pi */
# define M_2_PI         0.63661977236758134308  /* 2/pi */
# define M_2_SQRTPI     1.12837916709551257390  /* 2/sqrt(pi) */
# define M_SQRT2        1.41421356237309504880  /* sqrt(2) */
# define M_SQRT1_2      0.70710678118654752440  /* 1/sqrt(2) */
#endif

/*
 * round
 */
inline NS_HIDDEN_(double) NS_round(double x)
{
    return x >= 0.0 ? floor(x + 0.5) : ceil(x - 0.5);
}
inline NS_HIDDEN_(float) NS_roundf(float x)
{
    return x >= 0.0f ? floorf(x + 0.5f) : ceilf(x - 0.5f);
}
inline NS_HIDDEN_(PRInt32) NS_lround(double x)
{
    return x >= 0.0 ? PRInt32(x + 0.5) : PRInt32(x - 0.5);
}

/* NS_roundup30 rounds towards infinity for positive and       */
/* negative numbers.                                           */

#if defined(XP_WIN32) && defined(_M_IX86) && !defined(__GNUC__)
inline NS_HIDDEN_(PRInt32) NS_lroundup30(float x)
{
    /* Code derived from Laurent de Soras' paper at             */
    /* http://ldesoras.free.fr/doc/articles/rounding_en.pdf     */

    /* Rounding up on Windows is expensive using the float to   */
    /* int conversion and the floor function. A faster          */
    /* approach is to use f87 rounding while assuming the       */
    /* default rounding mode of rounding to the nearest         */
    /* integer. This rounding mode, however, actually rounds    */
    /* to the nearest integer so we add the floating point      */
    /* number to itself and add our rounding factor before      */
    /* doing the conversion to an integer. We then do a right   */
    /* shift of one bit on the integer to divide by two.        */

    /* This routine doesn't handle numbers larger in magnitude  */
    /* than 2^30 but this is fine for NSToCoordRound because    */
    /* Coords are limited to 2^30 in magnitude.                 */

    static const double round_to_nearest = 0.5f;
    int i;

    __asm {
      fld     x                   ; load fp argument
      fadd    st, st(0)           ; double it
      fadd    round_to_nearest    ; add the rounding factor
      fistp   dword ptr i         ; convert the result to int
    }
    return i >> 1;                /* divide by 2 */
}
#endif /* XP_WIN32 && _M_IX86 && !__GNUC__ */

inline NS_HIDDEN_(PRInt32) NS_lroundf(float x)
{
    return x >= 0.0f ? PRInt32(x + 0.5f) : PRInt32(x - 0.5f);
}

/*
 * ceil
 */
inline NS_HIDDEN_(double) NS_ceil(double x)
{
    return ceil(x);
}
inline NS_HIDDEN_(float) NS_ceilf(float x)
{
    return ceilf(x);
}

/*
 * floor
 */
inline NS_HIDDEN_(double) NS_floor(double x)
{
    return floor(x);
}
inline NS_HIDDEN_(float) NS_floorf(float x)
{
    return floorf(x);
}

/*
 * hypot.  We don't need a super accurate version of this, if a platform
 * turns up with none of the possibilities below it would be okay to fall
 * back to sqrt(x*x + y*y).
 */
inline NS_HIDDEN_(double) NS_hypot(double x, double y)
{
#if __GNUC__ >= 4
    return __builtin_hypot(x, y);
#elif defined _WIN32
    return _hypot(x, y);
#else
    return hypot(x, y);
#endif
}

#endif