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Annotation of coherent/b/lib/libc/gen/ieee_d.c, revision 1.1.1.1

1.1       root        1: /*
                      2:  * libc/gen/ieee_d.c
                      3:  */
                      4: 
                      5: /*
                      6:  * ieee_d(double *idp, double *ddp)
                      7:  * Convert double from DECVAX format to IEEE format.
                      8:  * ddp points to a DECVAX format double to convert.
                      9:  * idp points to a destination for the converted IEEE value;
                     10:  * idp may be identical to ddp for in-place conversion.
                     11:  * The DECVAX significand is truncated, not rounded.
                     12:  * Always returns 0, because the conversion always succeeds.
                     13:  */
                     14: 
                     15: int
                     16: ieee_d(idp, ddp) double *idp, *ddp;
                     17: {
                     18:        unsigned char a[8];
                     19:        register unsigned char *cp;
                     20:        register int exp;
                     21: 
                     22:        /* Extract biased exponent. */
                     23:        cp = (char *)ddp;
                     24:        exp = ((cp[7] & 0x7F) << 1) | ((cp[6] & 0x80) >> 7);
                     25: 
                     26:        if (exp == 0) {
                     27:                memset((char *)idp, 0, 8);      /* set idp to 0.0 */
                     28:                return 0;
                     29:        }
                     30: 
                     31:        /* Adjust exponent bias and repack. */
                     32:        exp += 1023 - 129;
                     33:        a[7] = (cp[7] & 0x80) | (exp >> 4);
                     34:        a[6] = ((exp & 0x0F) << 4)  | ((cp[6] & 0x78) >> 3);
                     35:        a[5] = ((cp[6] & 0x7) << 5) | ((cp[5] & 0x7F) >> 3);
                     36:        a[4] = ((cp[5] & 0x7) << 5) | ((cp[4] & 0x7F) >> 3);
                     37:        a[3] = ((cp[4] & 0x7) << 5) | ((cp[3] & 0x7F) >> 3);
                     38:        a[2] = ((cp[3] & 0x7) << 5) | ((cp[2] & 0x7F) >> 3);
                     39:        a[1] = ((cp[2] & 0x7) << 5) | ((cp[1] & 0x7F) >> 3);
                     40:        a[0] = ((cp[1] & 0x7) << 5) | ((cp[0] & 0x7F) >> 3);
                     41: 
                     42:        /* Done, copy to destination. */
                     43:        memcpy((char *)idp, a, 8);
                     44:        return 0;
                     45: }
                     46: 
                     47: /* end of libc/gen/ieee_d.c */

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