4.3BSD - /usr/src/new/cpm/src/ffc.c

   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

Defined functions

Defined variables