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

     1  #include <math.h>
     2  #include <stdint.h>
     3  
     4  float remquof(float x, float y, int *quo)
     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  	int sx = ux.i>>31;
    10  	int sy = uy.i>>31;
    11  	uint32_t q;
    12  	uint32_t i;
    13  	uint32_t uxi = ux.i;
    14  
    15  	*quo = 0;
    16  	if (uy.i<<1 == 0 || isnan(y) || ex == 0xff)
    17  		return (x*y)/(x*y);
    18  	if (ux.i<<1 == 0)
    19  		return x;
    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  	q = 0;
    38  	if (ex < ey) {
    39  		if (ex+1 == ey)
    40  			goto end;
    41  		return x;
    42  	}
    43  
    44  	/* x mod y */
    45  	for (; ex > ey; ex--) {
    46  		i = uxi - uy.i;
    47  		if (i >> 31 == 0) {
    48  			uxi = i;
    49  			q++;
    50  		}
    51  		uxi <<= 1;
    52  		q <<= 1;
    53  	}
    54  	i = uxi - uy.i;
    55  	if (i >> 31 == 0) {
    56  		uxi = i;
    57  		q++;
    58  	}
    59  	if (uxi == 0)
    60  		ex = -30;
    61  	else
    62  		for (; uxi>>23 == 0; uxi <<= 1, ex--);
    63  end:
    64  	/* scale result and decide between |x| and |x|-|y| */
    65  	if (ex > 0) {
    66  		uxi -= 1U << 23;
    67  		uxi |= (uint32_t)ex << 23;
    68  	} else {
    69  		uxi >>= -ex + 1;
    70  	}
    71  	ux.i = uxi;
    72  	x = ux.f;
    73  	if (sy)
    74  		y = -y;
    75  	if (ex == ey || (ex+1 == ey && (2*x > y || (2*x == y && q%2)))) {
    76  		x -= y;
    77  		q++;
    78  	}
    79  	q &= 0x7fffffff;
    80  	*quo = sx^sy ? -(int)q : (int)q;
    81  	return sx ? -x : x;
    82  }