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circuitpython/lib/libm_dbl/floor.c

31 lines
653 B

#include "libm.h"
#if FLT_EVAL_METHOD==0 || FLT_EVAL_METHOD==1
#define EPS DBL_EPSILON
#elif FLT_EVAL_METHOD==2
#define EPS LDBL_EPSILON
#endif
static const double_t toint = 1/EPS;
double floor(double x)
{
union {double f; uint64_t i;} u = {x};
int e = u.i >> 52 & 0x7ff;
double_t y;
if (e >= 0x3ff+52 || x == 0)
return x;
/* y = int(x) - x, where int(x) is an integer neighbor of x */
if (u.i >> 63)
y = x - toint + toint - x;
else
y = x + toint - toint - x;
/* special case because of non-nearest rounding modes */
if (e <= 0x3ff-1) {
FORCE_EVAL(y);
return u.i >> 63 ? -1 : 0;
}
if (y > 0)
return x + y - 1;
return x + y;
}