shithub: npe

ref: 16bd4782f88ee554cba6c749a632c1c2296369d3
dir: /libnpe/trunc.c/

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#include <math.h>

double
trunc(double x)
{
	union {double f; u64int i;} u = {x};
	int e = (int)(u.i >> 52 & 0x7ff) - 0x3ff + 12;
	u64int m;

	if(e >= 52 + 12)
		return x;
	if(e < 12)
		e = 1;
	m = -1ULL >> e;
	if((u.i & m) == 0)
		return x;
	u.i &= ~m;

	return u.f;
}