fpmath.h

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/*
 * This file is part of LibCSS.
 * Licensed under the MIT License,
 *                http://www.opensource.org/licenses/mit-license.php
 * Copyright 2008 John-Mark Bell <jmb@netsurf-browser.org>
 */
 
#ifndef libcss_fpmath_h_
#define libcss_fpmath_h_
 
#ifdef __cplusplus
extern "C"
{
#endif
 
#include <stdint.h>
#include <limits.h>
 
/* 22:10 fixed point math */
#define CSS_RADIX_POINT 10
 
/* type for fixed point numbers */
typedef int32_t css_fixed;
 
static inline css_fixed
css_add_fixed(const css_fixed x, const css_fixed y) {
        int32_t ux = x;
        int32_t uy = y;
        int32_t res = ux + uy;
 
        /* Calculate overflowed result. (Don't change the sign bit of ux) */
        ux = (ux >> 31) + INT_MAX;
 
        /* Force compiler to use cmovns instruction */
        if ((int32_t) ((ux ^ uy) | ~(uy ^ res)) >= 0) {
                res = ux;
        }
 
        return res;
}
 
static inline css_fixed
css_subtract_fixed(const css_fixed x, const css_fixed y) {
        int32_t ux = x;
        int32_t uy = y;
        int32_t res = ux - uy;
 
        ux = (ux >> 31) + INT_MAX;
 
        /* Force compiler to use cmovns instruction */
        if ((int32_t)((ux ^ uy) & (ux ^ res)) < 0) {
                res = ux;
        }
 
        return res;
}
 
static inline css_fixed
css_divide_fixed(const css_fixed x, const css_fixed y) {
        int64_t xx = ((int64_t)x * (1 << CSS_RADIX_POINT)) / y;
 
        if (xx < INT_MIN)
                xx = INT_MIN;
 
        if (xx > INT_MAX)
                xx = INT_MAX;
 
        return xx;
}
 
static inline css_fixed
css_multiply_fixed(const css_fixed x, const css_fixed y) {
        int64_t xx = ((int64_t)x * (int64_t)y) >> CSS_RADIX_POINT;
 
        if (xx < INT_MIN)
                xx = INT_MIN;
 
        if (xx > INT_MAX)
                xx = INT_MAX;
 
        return xx;
}
 
static inline css_fixed
css_int_to_fixed(const int a) {
        int64_t xx = ((int64_t) a) * (1 << CSS_RADIX_POINT);
 
        if (xx < INT_MIN)
                xx = INT_MIN;
 
        if (xx > INT_MAX)
                xx = INT_MAX;
 
        return xx;
}
 
static inline css_fixed
css_float_to_fixed(const float a) {
        float xx = a * (float) (1 << CSS_RADIX_POINT);
 
        if (xx < INT_MIN)
                return INT_MIN;
 
        /* Conversion from int to float changes value from
         * 2147483647 to 2147483648, so we use >= instead of >. */
        if (xx >= (float)INT_MAX)
                return INT_MAX;
 
        return (css_fixed) xx;
}
 
/* Add two fixed point values */
#define FADD(a, b) (css_add_fixed((a), (b)))
/* Subtract two fixed point values */
#define FSUB(a, b) (css_subtract_fixed((a), (b)))
/* Multiply two fixed point values */
#define FMUL(a, b) (css_multiply_fixed((a), (b)))
/* Divide two fixed point values */
#define FDIV(a, b) (css_divide_fixed((a), (b)))
 
/* Convert a floating point value to fixed point */
#define FLTTOFIX(a) ((css_fixed) ((a) * (float) (1 << CSS_RADIX_POINT)))
/* Convert a fixed point value to floating point */
#define FIXTOFLT(a) ((float) (a) / (float) (1 << CSS_RADIX_POINT))
 
/* Convert an integer to a fixed point value */
#define INTTOFIX(a) (css_int_to_fixed(a))
/* Convert a fixed point value to an integer */
#define FIXTOINT(a) ((a) >> CSS_RADIX_POINT)
 
/* truncate a fixed point value */
#define TRUNCATEFIX(a) (a & ~((1 << CSS_RADIX_POINT)- 1 ))
/* get fractional component of a fixed point value */
#define FIXFRAC(a) (a & ((1 << CSS_RADIX_POINT)- 1 ))
 
/* Useful values */
#define F_PI_2  0x00000648      /* 1.5708 (PI/2) */
#define F_PI    0x00000c91      /* 3.1415 (PI) */
#define F_3PI_2 0x000012d9      /* 4.7124 (3PI/2) */
#define F_2PI   0x00001922      /* 6.2831 (2 PI) */
 
#define F_90    0x00016800      /*  90 */
#define F_180   0x0002d000      /* 180 */
#define F_270   0x00043800      /* 270 */
#define F_360   0x0005a000      /* 360 */
 
#define F_0_5   0x00000200      /* 0.5 */
#define F_1     0x00000400      /*   1 */
#define F_10    0x00002800      /*  10 */
#define F_72    0x00012000      /*  72 */
#define F_96    0x00018000      /*  96 */
#define F_100   0x00019000      /* 100 */
#define F_200   0x00032000      /* 200 */
#define F_255   0x0003FC00      /* 255 */
#define F_300   0x0004b000      /* 300 */
#define F_400   0x00064000      /* 400 */
 
/* Fixed point percentage `p` of integer `i`, to an integer */
#define FPCT_OF_INT_TOINT(p, i) (FIXTOINT(FDIV((p * i), F_100)))
 
#ifdef __cplusplus
}
#endif
 
#endif