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Annotation of 43BSD/contrib/icon/rt/hash.c, revision 1.1

1.1     ! root        1: #include "../h/rt.h"
        !             2: 
        !             3: /*
        !             4:  * hash - compute hash value of arbitrary object for table and set accessing.
        !             5:  */
        !             6: 
        !             7: hash(d)
        !             8: struct descrip *d;
        !             9:    {
        !            10:    register int i, j;
        !            11:    register char *s;
        !            12: 
        !            13:    if (QUAL(*d)) {
        !            14:       /*
        !            15:        * Compute the hash value for the string by summing the value
        !            16:        *  of all the characters (up to a maximum of 10) plus the length.
        !            17:        */
        !            18:       i = 0;
        !            19:       s = STRLOC(*d);
        !            20:       j = STRLEN(*d);
        !            21:       for (j = (j <= 10) ? j : 10 ; j > 0; j--)
        !            22:          i += *s++ & 0377;
        !            23:       i += STRLEN(*d) & 0377;
        !            24:       }
        !            25:    else {
        !            26:       switch (TYPE(*d)) {
        !            27:          /*
        !            28:           * The hash value for numeric types is the bitstring representation
        !            29:           *  of the value.
        !            30:           */
        !            31:          case T_INTEGER:
        !            32:             i = INTVAL(*d);
        !            33:             break;
        !            34: 
        !            35: #ifdef LONGS
        !            36:          case T_LONGINT:
        !            37:             i = BLKLOC(*d)->longint.intval;
        !            38:             break;
        !            39: 
        !            40: #endif LONGS
        !            41:          case T_REAL:
        !            42:             i = BLKLOC(*d)->realblk.realval;
        !            43:             break;
        !            44: 
        !            45:          case T_CSET:
        !            46:             /*
        !            47:              * Compute the hash value for a cset by exclusive or-ing the
        !            48:              *  words in the bit array.
        !            49:              */
        !            50:             i = 0;
        !            51:             for (j = 0; j < CSETSIZE; j++)
        !            52:                i ^= BLKLOC(*d)->cset.bits[j];
        !            53:             break;
        !            54: 
        !            55:          default:
        !            56:             /*
        !            57:              * For other types, just use the type value as the hash
        !            58:              *  value.  This produces loads of collisions, but that's
        !            59:              *  why collision insurance is mandatory.
        !            60:              */
        !            61:             i = TYPE(*d);
        !            62:             break;
        !            63:          }
        !            64:       }
        !            65:    /*
        !            66:     * Return the hash value as a positive number.
        !            67:     */
        !            68:    return ((unsigned)i);
        !            69:    }

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