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

1.1     ! root        1: /*
        !             2:  * libc/gen/decvax_d.c
        !             3:  */
        !             4: 
        !             5: /*
        !             6:  * decvax_d(double *ddp, double *idp)
        !             7:  * Convert double from IEEE format to DECVAX format.
        !             8:  * idp points to an IEEE format double to convert.
        !             9:  * ddp points to a destination for the converted DECVAX value;
        !            10:  * ddp may be identical to idp for in-place conversion.
        !            11:  * Returns 0 on success, -1 on underflow, 1 on overflow.
        !            12:  */
        !            13: 
        !            14: int
        !            15: decvax_d(ddp, idp) double *ddp, *idp;
        !            16: {
        !            17:        unsigned char a[8];
        !            18:        register unsigned char *cp;
        !            19:        register int exp, a0123456;
        !            20: 
        !            21:        /* Extract sign, biased exponent. */
        !            22:        cp = (char *)idp;
        !            23:        exp = ((cp[7] & 0x7F) << 4) | ((cp[6] & 0xF0) >> 4);
        !            24:        if (exp == 0) {
        !            25:                a0123456 = (a[6] & 0x0F) | a[5] | a[4] | a[3] | a[2] | a[1] | a[0];
        !            26:                memset((char *)ddp, 0, 8);              /* set to 0.0 */
        !            27:                return (a0123456 == 0) ? 0 : -1;        /* return -1 for denormals */
        !            28:        }
        !            29: 
        !            30:        /* Adjust exponent bias. */
        !            31:        exp -= 1023 - 129;
        !            32:        if (exp <= 0) {
        !            33:                memset((char *)ddp, 0, 8);      /* set to 0.0 */
        !            34:                return -1;                      /* underflow */
        !            35:        } else if (exp > 255) {
        !            36:                /* Overflow, also used for NaNs. */
        !            37:                cp = (char *)ddp;
        !            38:                memset(cp, 0xFF, 7);            /* set to max */
        !            39:                cp[7] |= 0x7F;                  /* preserving sign bit */
        !            40:                return 1;                       /* overflow */
        !            41:        }
        !            42: 
        !            43:        /* Repack. */
        !            44:        a[7] = (cp[7] & 0x80) | ((exp & 0xFE) >> 1);
        !            45:        a[6] = ((exp & 1) << 7) | ((cp[6] & 0x0F) << 3) | ((cp[5] & 0xE0) >> 5);
        !            46:        a[5] = ((cp[5] & 0x1F) << 3) | ((cp[4] & 0xE0) >> 5);
        !            47:        a[4] = ((cp[4] & 0x1F) << 3) | ((cp[3] & 0xE0) >> 5);
        !            48:        a[3] = ((cp[3] & 0x1F) << 3) | ((cp[2] & 0xE0) >> 5);
        !            49:        a[2] = ((cp[2] & 0x1F) << 3) | ((cp[1] & 0xE0) >> 5);
        !            50:        a[1] = ((cp[1] & 0x1F) << 3) | ((cp[0] & 0xE0) >> 5);
        !            51:        a[0] = ((cp[0] & 0x1F) << 3);
        !            52:        memcpy((char *)ddp, a, 8);
        !            53:        return 0;
        !            54: }
        !            55: 
        !            56: /* end of libc/gen/decvax_d.c */

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