usr/src/lib/libc/vax/string/rindex.s

/*
 * Copyright (c) 1983 Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that the above copyright notice and this paragraph are
 * duplicated in all such forms and that any documentation,
 * advertising materials, and other materials related to such
 * distribution and use acknowledge that the software was developed
 * by the University of California, Berkeley.  The name of the
 * University may not be used to endorse or promote products derived
 * from this software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

#if defined(LIBC_SCCS) && !defined(lint)
        .asciz "@(#)rindex.s    5.5 (Berkeley) %G%"
#endif /* LIBC_SCCS and not lint */

/*
 * Find the last occurence of c in the string cp.
 * Return pointer to match or null pointer.
 *
 * char *
 * rindex(cp, c)
 *      char *cp, c;
 */
#include "DEFS.h"

ENTRY(rindex, 0)
        movq    4(ap),r1        # r1 = cp; r2 = c
        tstl    r2              # check for special case c == '\0'
        bneq    2f
1:
        locc    $0,$65535,(r1)  # just find end of string
        beql    1b              # still looking
        movl    r1,r0           # found it
        ret
2:
        moval   tbl,r3          # r3 = address of table
        bbss    $0,(r3),5f      # insure not reentering
        movab   (r3)[r2],r5     # table entry for c
        incb    (r5)
        clrl    r4              # last found
3:
        scanc   $65535,(r1),(r3),$1     # look for c or '\0'
        beql    3b              # keep looking
        tstb    (r1)            # if have found '\0'
        beql    4f              #    we are done
        movl    r1,r4           # save most recently found
        incl    r1              # skip over character
        jbr     3b              # keep looking
4:
        movl    r4,r0           # return last found (if any)
        clrb    (r5)            # clean up table
        clrb    (r3)
        ret

        .data
tbl:    .space  256
        .text

/*
 * Reentrant, but slower version of rindex
 */
5:
        movl    r1,r3
        clrl    r4              # r4 = pointer to last match
6:
        locc    $0,$65535,(r3)  # look for '\0'
        bneq    8f
        decw    r0              # r0 = 65535
1:
        locc    r2,r0,(r3)      # look for c
        bneq    7f
        movl    r1,r3           # reset pointer and ...
        jbr     6b              # ... try again
7:
        movl    r1,r4           # stash pointer ...
        addl3   $1,r1,r3        # ... skip over match and ...
        decl    r0              # ... decrement count
        jbr     6b              # ... try again
8:
        subl3   r3,r1,r0        # length of short block
        incl    r0              # +1 for '\0'
9:
        locc    r2,r0,(r3)      # look for c
        beql    0f
        movl    r1,r4           # stash pointer ...
        addl3   $1,r1,r3        # ... skip over match ...
        decl    r0              # ... adjust count and ...
        jbr     9b              # ... try again
0:
        movl    r4,r0           # return stashed pointer
        ret