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Annotation of 43BSD/lib/libc/vax/gen/strncmp.s, revision 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  "@(#)strncmp.s  5.3 (Berkeley) 3/9/86"
        !             9: #endif LIBC_SCCS
        !            10: 
        !            11: /*
        !            12:  * Compare at most n characters of string
        !            13:  * s1 lexicographically to string s2.
        !            14:  * Return:
        !            15:  *     0       s1 == s2
        !            16:  *     > 0     s1 > s2
        !            17:  *     < 0     s2 < s2
        !            18:  *
        !            19:  * strncmp(s1, s2, n)
        !            20:  *     char *s1, *s2;
        !            21:  *     int n;
        !            22:  */
        !            23: #include "DEFS.h"
        !            24: 
        !            25: ENTRY(strncmp, 0)
        !            26:        movl    4(ap),r1        # r1 = s1
        !            27:        movq    8(ap),r3        # r3 = s2; r4 = n
        !            28: 1:
        !            29:        clrl    r5              # calculate min bytes to next page boundry
        !            30:        subb3   r1,$255,r5      # r5 = (bytes - 1) to end of page for s1
        !            31:        subb3   r3,$255,r0      # r0 = (bytes - 1) to end of page for s2
        !            32:        cmpb    r0,r5           # r5 = min(r0, r5);
        !            33:        bgtru   2f
        !            34:        movb    r0,r5
        !            35: 2:
        !            36:        incl    r5              # r5 = min bytes to next page boundry
        !            37:        cmpl    r4,r5           # r5 = min(n, r5);
        !            38:        bgeq    3f
        !            39:        movl    r4,r5
        !            40: 3:
        !            41:        cmpc3   r5,(r1),(r3)    # compare strings
        !            42:        bneq    4f
        !            43:        subl2   r5,r4           # check for end of comparison
        !            44:        beql    5f
        !            45:        subl2   r5,r1           # check if found null yet
        !            46:        locc    $0,r5,(r1)
        !            47:        beql    1b              # not yet done, continue checking
        !            48:        subl2   r0,r3
        !            49:        mnegb   (r3),r0         # r0 = '\0' - *s2
        !            50:        cvtbl   r0,r0
        !            51:        ret
        !            52: 4:
        !            53:        subl2   r0,r5           # check for null in matching string
        !            54:        subl2   r5,r1
        !            55:        locc    $0,r5,(r1)
        !            56:        bneq    5f
        !            57:        subb3   (r3),(r1),r0    # r0 = *s1 - *s2
        !            58:        cvtbl   r0,r0
        !            59:        ret
        !            60: 5:
        !            61:        clrl    r0              # both the same to null
        !            62:        ret

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