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Fix HalfToFloat() and FloatToHalf() dereferencing issues with an union

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This commit is contained in:
asdqwe 2025-01-26 14:27:11 -03:00
parent 139de05e9d
commit e6f4d1cf2b
1 changed files with 16 additions and 5 deletions
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21
src/rtextures.c
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@ -5384,19 +5384,27 @@ int GetPixelDataSize(int width, int height, int format)
//---------------------------------------------------------------------------------- //----------------------------------------------------------------------------------
// Module specific Functions Definition // Module specific Functions Definition
//---------------------------------------------------------------------------------- //----------------------------------------------------------------------------------
union floatUnsignedUnion {
float fm;
unsigned int ui;
};
// Convert half-float (stored as unsigned short) to float // Convert half-float (stored as unsigned short) to float
// REF: https://stackoverflow.com/questions/1659440/32-bit-to-16-bit-floating-point-conversion/60047308#60047308 // REF: https://stackoverflow.com/questions/1659440/32-bit-to-16-bit-floating-point-conversion/60047308#60047308
static float HalfToFloat(unsigned short x) static float HalfToFloat(unsigned short x)
{ {
float result = 0.0f; float result = 0.0f;
union floatUnsignedUnion uni;
uni.fm = 0.0f;
const unsigned int e = (x & 0x7C00) >> 10; // Exponent const unsigned int e = (x & 0x7C00) >> 10; // Exponent
const unsigned int m = (x & 0x03FF) << 13; // Mantissa const unsigned int m = (x & 0x03FF) << 13; // Mantissa
const float fm = (float)m; uni.fm = (float)m;
const unsigned int v = (*(unsigned int *)&fm) >> 23; // Evil log2 bit hack to count leading zeros in denormalized format const unsigned int v = uni.ui >> 23; // Evil log2 bit hack to count leading zeros in denormalized format
const unsigned int r = (x & 0x8000) << 16 | (e != 0)*((e + 112) << 23 | m) | ((e == 0)&(m != 0))*((v - 37) << 23 | ((m << (150 - v)) & 0x007FE000)); // sign : normalized : denormalized uni.ui = (x & 0x8000) << 16 | (e != 0)*((e + 112) << 23 | m) | ((e == 0)&(m != 0))*((v - 37) << 23 | ((m << (150 - v)) & 0x007FE000)); // sign : normalized : denormalized
result = *(float *)&r; result = uni.fm;
return result; return result;
} }
@ -5406,7 +5414,10 @@ static unsigned short FloatToHalf(float x)
{ {
unsigned short result = 0; unsigned short result = 0;
const unsigned int b = (*(unsigned int *) & x) + 0x00001000; // Round-to-nearest-even: add last bit after truncated mantissa union floatUnsignedUnion uni;
uni.fm = x;
const unsigned int b = uni.ui + 0x00001000; // Round-to-nearest-even: add last bit after truncated mantissa
const unsigned int e = (b & 0x7F800000) >> 23; // Exponent const unsigned int e = (b & 0x7F800000) >> 23; // Exponent
const unsigned int m = b & 0x007FFFFF; // Mantissa; in line below: 0x007FF000 = 0x00800000-0x00001000 = decimal indicator flag - initial rounding const unsigned int m = b & 0x007FFFFF; // Mantissa; in line below: 0x007FF000 = 0x00800000-0x00001000 = decimal indicator flag - initial rounding