github.com/afumu/libc@v0.0.6/musl/src/math/fmodf.c (about)

     1  #include <math.h>
     2  #include <stdint.h>
     3  
     4  float fmodf(float x, float y)
     5  {
     6  	union {float f; uint32_t i;} ux = {x}, uy = {y};
     7  	int ex = ux.i>>23 & 0xff;
     8  	int ey = uy.i>>23 & 0xff;
     9  	uint32_t sx = ux.i & 0x80000000;
    10  	uint32_t i;
    11  	uint32_t uxi = ux.i;
    12  
    13  	if (uy.i<<1 == 0 || isnan(y) || ex == 0xff)
    14  		return (x*y)/(x*y);
    15  	if (uxi<<1 <= uy.i<<1) {
    16  		if (uxi<<1 == uy.i<<1)
    17  			return 0*x;
    18  		return x;
    19  	}
    20  
    21  	/* normalize x and y */
    22  	if (!ex) {
    23  		for (i = uxi<<9; i>>31 == 0; ex--, i <<= 1);
    24  		uxi <<= -ex + 1;
    25  	} else {
    26  		uxi &= -1U >> 9;
    27  		uxi |= 1U << 23;
    28  	}
    29  	if (!ey) {
    30  		for (i = uy.i<<9; i>>31 == 0; ey--, i <<= 1);
    31  		uy.i <<= -ey + 1;
    32  	} else {
    33  		uy.i &= -1U >> 9;
    34  		uy.i |= 1U << 23;
    35  	}
    36  
    37  	/* x mod y */
    38  	for (; ex > ey; ex--) {
    39  		i = uxi - uy.i;
    40  		if (i >> 31 == 0) {
    41  			if (i == 0)
    42  				return 0*x;
    43  			uxi = i;
    44  		}
    45  		uxi <<= 1;
    46  	}
    47  	i = uxi - uy.i;
    48  	if (i >> 31 == 0) {
    49  		if (i == 0)
    50  			return 0*x;
    51  		uxi = i;
    52  	}
    53  	for (; uxi>>23 == 0; uxi <<= 1, ex--);
    54  
    55  	/* scale result up */
    56  	if (ex > 0) {
    57  		uxi -= 1U << 23;
    58  		uxi |= (uint32_t)ex << 23;
    59  	} else {
    60  		uxi >>= -ex + 1;
    61  	}
    62  	uxi |= sx;
    63  	ux.i = uxi;
    64  	return ux.f;
    65  }