#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <wtypes.h>
#define FP_BITS(fp) (*(DWORD *)&(fp))
#define FP_ABS_BITS(fp) (FP_BITS(fp)&0x7FFFFFFF)
#define FP_SIGN_BIT(fp) (FP_BITS(fp)&0x80000000)
#define FP_ONE_BITS 0x3F800000
// r = 1/p
#define FP_INV(r,p) \
{ \
 int _i = 2 * FP_ONE_BITS - *(int *)&(p); \
 r = *(float *)&_i; \
 r = r * (2.0f - (p) * r); \
}
#define FP_EXP(e,p) \
{ \
 int _i; \
 e = -1.44269504f * (float)0x00800000 * (p); \
 _i = (int)e + 0x3F800000; \
 e = *(float *)&_i; \
}
#define FP_NORM_TO_BYTE(i,p) \
{ \
 float _n = (p) + 1.0f; \
 i = *(int *)&_n; \
 if (i>= 0x40000000) i = 0xFF; \
 else if (i <=0x3f800000) i = 0; \ else i = ((i)>> 15) & 0xFF; \
}
inline unsigned long FP_NORM_TO_BYTE2(float p) 
{ 
 float fpTmp = p + 1.0f; 
 return ((*(unsigned *)&fpTmp)>> 15) & 0xFF; 
}
inline unsigned long FP_NORM_TO_BYTE3(float p) 
{
 float ftmp = p + 12582912.0f; 
 return ((*(unsigned long *)&ftmp) & 0xFF);
}
static unsigned int fast_sqrt_table[0x10000]; // declare table of square roots 
typedef union FastSqrtUnion
{
 float f;
 unsigned int i;
} FastSqrtUnion;
void build_sqrt_table()
{
 unsigned int i;
 FastSqrtUnion s;
 
 for (i = 0; i <= 0x7FFF; i++) { // Build a float with the bit pattern i as mantissa // and an exponent of 0, stored as 127 s.i = (i << 8) &#124; (0x7F << 23); s.f = (float)sqrt(s.f); // Take the square root then strip the first 7 bits of // the mantissa into the table fast_sqrt_table[i + 0x8000] = (s.i & 0x7FFFFF); // Repeat the process, this time with an exponent of 1, // stored as 128 s.i = (i << 8) &#124; (0x80 << 23); s.f = (float)sqrt(s.f); fast_sqrt_table[i] = (s.i & 0x7FFFFF); } } inline float fastsqrt(float n) { if (FP_BITS(n) == 0) return 0.0; // check for square root of 0 FP_BITS(n) = fast_sqrt_table[(FP_BITS(n)>> 8) & 0xFFFF] &#124; ((((FP_BITS(n) - 0x3F800000)>> 1) + 0x3F800000) & 0x7F800000);
 
 return n;
}
// At the assembly level the recommended workaround for the second FIST bug is the same for the first; 
// inserting the FRNDINT instruction immediately preceding the FIST instruction. 
__forceinline void FloatToInt(int *int_pointer, float f) 
{
 __asm fld f
 __asm mov edx,int_pointer
 __asm FRNDINT
 __asm fistp dword ptr [edx];
}
int main(int argc, char* argv[])
{
 float t, it, test_sqrt;
 int i = 0;
 build_sqrt_table();
 t = 1234.121234f;
 
 test_sqrt = fastsqrt(t);
 printf("sqrt expected %20.10f approx %20.10f\n", sqrt(t), test_sqrt);
 FP_INV(it,t);
 printf("inv expected %20.10f approx %20.10f\n", 1/t, it);
 i = 0xdeafbabe;
 FloatToInt(&i, t);
 printf("ftol expected %d actual %d %08X\n", (int)t, i, i);
 return 0;
}
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