kolibrios/programs/develop/ktcc/trunk/libc.obj/source/math/frexp.c

/* Copyright (C) 1994 DJ Delorie, see COPYING.DJ for details */
#include <math.h>

double frexp(double x, int* exptr)
{
    union {
        double d;
        unsigned char c[8];
    } u;

    u.d = x;
    /*
     * The format of the number is:
     * Sign, 12 exponent bits, 51 mantissa bits
     * The exponent is 1023 biased and there is an implicit zero.
     * We get the exponent from the upper bits and set the exponent
     * to 0x3fe (1022).
     */
    *exptr = (int)(((u.c[7] & 0x7f) << 4) | (u.c[6] >> 4)) - 1022;
    u.c[7] &= 0x80;
    u.c[7] |= 0x3f;
    u.c[6] &= 0x0f;
    u.c[6] |= 0xe0;
    return u.d;
}