diff options
Diffstat (limited to 'src/zopflipng/lodepng/lodepng_util.cpp')
| -rw-r--r-- | src/zopflipng/lodepng/lodepng_util.cpp | 22 |
1 files changed, 17 insertions, 5 deletions
diff --git a/src/zopflipng/lodepng/lodepng_util.cpp b/src/zopflipng/lodepng/lodepng_util.cpp index 9ceebe7..bfee116 100644 --- a/src/zopflipng/lodepng/lodepng_util.cpp +++ b/src/zopflipng/lodepng/lodepng_util.cpp @@ -277,9 +277,15 @@ void* lodepng_malloc(size_t size); void lodepng_free(void* ptr); #endif /*LODEPNG_COMPILE_ALLOCATORS*/ -/* avoid needing <float.h> for FLT_MAX */ +/* avoid needing <float.h> for FLT_MAX. This assumes IEEE 32-bit float. */ static const float lodepng_flt_max = 3.40282346638528859811704183484516925e38f; +/* define infinity and NaN in a way compatible with ANSI C90 (no INFINITY or NAN macros) yet also with visual studio */ +/* visual studio doesn't allow division through zero literal, but allows it through variable set to zero */ +static const float lodepng_flt_zero_ = 0.0f; +static const float lodepng_flt_inf = 1.0f / lodepng_flt_zero_; /* infinity */ +static const float lodepng_flt_nan = 0.0f / lodepng_flt_zero_; /* not a number */ + /* powf polyfill, 5-6 digits accurate, 33% slower than powf, assumes IEEE 32-bit float, but other than that multiplatform and no math lib needed (note: powf also isn't in ISO C90, and pow is slower). */ @@ -296,11 +302,17 @@ static float lodepng_powf(float x, float y) { } else { if(!(y < -1073741824.0f || y > 1073741824.0f)) { /* large y always even integer, but cast would overflow */ i = (int)y; - if(i != y) return (x < -lodepng_flt_max) ? (y < 0 ? 0 : (1 / 0.0f)) : (x == 0 ? (y < 0 ? 1 / 0.0f : 0) : (0 / 0.0f)); + if(i != y) { + return (x < -lodepng_flt_max) ? (y < 0 ? 0 : lodepng_flt_inf) : + (x == 0 ? (y < 0 ? lodepng_flt_inf : 0) : lodepng_flt_nan); + } if(i & 1) return x == 0 ? (y < 0 ? (1 / x) : x) : -lodepng_powf(-x, y); } - if(x == 0) return y <= 0 ? (1 / 0.0f) : 0; - if(x < -lodepng_flt_max) return y <= 0 ? (y == 0 ? 1 : 0) : ((i & 1) ? (-1 / 0.0f) : (1 / 0.0f)); /* x = -infinity */ + if(x == 0) return y <= 0 ? lodepng_flt_inf : 0; + if(x < -lodepng_flt_max) { /* x == -infinity */ + return y <= 0 ? (y == 0 ? 1 : 0) : ((i & 1) ? + -lodepng_flt_inf : lodepng_flt_inf); + } x = -x; if(x == 1) return 1; } @@ -319,7 +331,7 @@ static float lodepng_powf(float x, float y) { x *= y; /* using the formula exp2(y * log2(x)) */ - if(!(x > -128.0f && x < 128.0f)) return x > 0 ? (1 / 0.0f) : 0; /* prevent int overflow */ + if(!(x > -128.0f && x < 128.0f)) return x > 0 ? lodepng_flt_inf : 0; /* prevent int overflow */ i = (int)x; x -= i; /* polynomial to approximate exp2(x) with x in range -1..1 */ |