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Annotation of 43BSD/contrib/cpm/src/ffc.c, revision 1.1.1.1

1.1       root        1: /*     ffc.c   1.4     83/05/13        */
                      2: 
                      3: /*
                      4:  * If used on a vax (i.e., VAX is defined), this routine simply executes
                      5:  * the VAX find-first-set instruction.
                      6:  * Usage:
                      7:  *     int startbit, field_lth, field, result;
                      8:  *     result = ffc(startbit,field_lth,field);
                      9:  *
                     10:  * startbit is the bit number of the field to start the search,
                     11:  *             the rightmost bit is number one.
                     12:  * field_lth is the length of the field in bits.
                     13:  * field is the actual field
                     14:  * result is the resulting bit number,
                     15:  *             e.g. the number of the first clear bit in the field.
                     16:  * hs 10/29/82
                     17:  */
                     18: 
                     19: ffc(start, len, field)
                     20: 
                     21: #ifndef VAX
                     22:        register long field;
                     23:        int start, len;
                     24: {
                     25:        register int i;
                     26: 
                     27:        for (i=start; i<len; i++) {
                     28:                if ((field&1) == 0)
                     29:                        break;
                     30:                field >>= 1;
                     31:        }
                     32:        return (i);
                     33: }
                     34: #else
                     35: 
                     36:        int start, len, field;
                     37: {
                     38:        asm("ffc        4(ap),8(ap),12(ap),r0");
                     39:        return;
                     40: }
                     41: #endif

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