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Annotation of 43BSD/lib/libc/vax/gen/strncpy.s, revision 1.1.1.1

1.1       root        1: /*
                      2:  * Copyright (c) 1983 Regents of the University of California.
                      3:  * All rights reserved.  The Berkeley software License Agreement
                      4:  * specifies the terms and conditions for redistribution.
                      5:  */
                      6: 
                      7: #ifdef LIBC_SCCS
                      8:        .asciz  "@(#)strncpy.s  5.3 (Berkeley) 3/9/86"
                      9: #endif LIBC_SCCS
                     10: 
                     11: /*
                     12:  * Copy string s2 over top of string s1.
                     13:  * Truncate or null-pad to n bytes.
                     14:  *
                     15:  * char *
                     16:  * strncpy(s1, s2, n)
                     17:  *     char *s1, *s2;
                     18:  */
                     19: #include "DEFS.h"
                     20: 
                     21: ENTRY(strncpy, R6)
                     22:        movl    12(ap),r6       # r6 = n
                     23:        bleq    done            # n <= 0
                     24:        movl    4(ap),r3        # r3 = s1
                     25:        movl    8(ap),r1        # r1 = s2
                     26: 1:
                     27:        movzwl  $65535,r2       # r2 = bytes in first chunk
                     28:        cmpl    r6,r2           # r2 = min(bytes in chunk, n);
                     29:        jgeq    2f
                     30:        movl    r6,r2
                     31: 2:
                     32:        subl2   r2,r6           # update n
                     33:        locc    $0,r2,(r1)      # '\0' found?
                     34:        jneq    3f
                     35:        subl2   r2,r1           # back up pointer updated by locc
                     36:        movc3   r2,(r1),(r3)    # copy in next piece
                     37:        tstl    r6              # run out of space?
                     38:        jneq    1b
                     39:        jbr     done
                     40: 3:                             # copy up to '\0' logic
                     41:        addl2   r0,r6           # r6 = number of null-pad bytes
                     42:        subl2   r0,r2           # r2 = number of bytes to move
                     43:        subl2   r2,r1           # back up pointer updated by locc
                     44:        movc3   r2,(r1),(r3)    # copy in last piece
                     45: 4:                             # null-pad logic
                     46:        movzwl  $65535,r2       # r2 = bytes in first chunk
                     47:        cmpl    r6,r2           # r2 = min(bytes in chunk, n);
                     48:        jgeq    5f
                     49:        movl    r6,r2
                     50: 5:
                     51:        subl2   r2,r6           # update n
                     52:        movc5   $0,(r3),$0,r2,(r3)# pad with '\0's
                     53:        tstl    r6              # finished padding?
                     54:        jneq    4b
                     55: done:
                     56:        movl    4(ap),r0        # return s1
                     57:        ret

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