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Annotation of coherent/b/lib/libc/gen/decvax_f.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * libc/gen/decvax_f.c
        !             3:  */
        !             4: 
        !             5: /*
        !             6:  * decvax_f(float *dfp, float *ifp)
        !             7:  * Convert float from IEEE format to DECVAX format.
        !             8:  * ifp points to an IEEE format float to convert.
        !             9:  * dfp points to a destination for the converted DECVAX value;
        !            10:  * dfp may be identical to ifp for in-place conversion.
        !            11:  * The significand remains unchanged.
        !            12:  * Returns 0 if successful, 1 on overflow.
        !            13:  */
        !            14: 
        !            15: int
        !            16: decvax_f(dfp, ifp) float *dfp, *ifp;
        !            17: {
        !            18:        register unsigned char *cp;
        !            19:        register int exp, a012;
        !            20: 
        !            21:        /* Copy to destination. */
        !            22:        cp = (char *)dfp;
        !            23:        if (dfp != ifp)
        !            24:                memcpy(cp, (char *)ifp, sizeof(float));
        !            25: 
        !            26:        /* Extract biased exponent. */
        !            27:        exp = ((cp[3] & 0x7F) << 1) | ((cp[2] & 0x80) >> 7);
        !            28: 
        !            29:        /* Adjust exponent bias from 127 to 129. */
        !            30:        if (exp == 0) {
        !            31:                a012 = (cp[2] & 0x0F) | cp[1] | cp[0];
        !            32:                memset((char *)dfp, 0, 4);      /* set to 0.0 */
        !            33:                return (a012 == 0) ? 0 : -1;    /* return -1 for denormals */
        !            34:        } else if (exp < 256) {
        !            35:                /* Add 2 by incrementing the low bit of the hi byte. */
        !            36:                ++cp[3];
        !            37:                return 0;
        !            38:        }
        !            39: 
        !            40:        /* Exponent overflow, also returned for NaNs. */
        !            41:        cp[3] |= 0x7F;
        !            42:        cp[2] = cp[1] = cp[0] = 0xFF;
        !            43:        return 1;
        !            44: }
        !            45: 
        !            46: /* end of libc/gen/decvax_f.c */

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