source: azure_iot_hub/trunk/musl-1.1.18/src/math/truncl.c@ 389

#include "libm.h"

#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
long double truncl(long double x)
{
        return trunc(x);
}
#elif (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384

static const long double toint = 1/LDBL_EPSILON;

long double truncl(long double x)
{
        union ldshape u = {x};
        int e = u.i.se & 0x7fff;
        int s = u.i.se >> 15;
        long double y;

        if (e >= 0x3fff+LDBL_MANT_DIG-1)
                return x;
        if (e <= 0x3fff-1) {
                FORCE_EVAL(x + 0x1p120f);
                return x*0;
        }
        /* y = int(|x|) - |x|, where int(|x|) is an integer neighbor of |x| */
        if (s)
                x = -x;
        y = x + toint - toint - x;
        if (y > 0)
                y -= 1;
        x += y;
        return s ? -x : x;
}
#endif