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Annotation of researchv10no/cmd/worm/scsi/tcl/strstr.c, revision 1.1.1.1

1.1       root        1: /* 
                      2:  * strstr.c --
                      3:  *
                      4:  *     Source code for the "strstr" library routine.
                      5:  *
                      6:  * Copyright 1988 Regents of the University of California
                      7:  * Permission to use, copy, modify, and distribute this
                      8:  * software and its documentation for any purpose and without
                      9:  * fee is hereby granted, provided that the above copyright
                     10:  * notice appear in all copies.  The University of California
                     11:  * makes no representations about the suitability of this
                     12:  * software for any purpose.  It is provided "as is" without
                     13:  * express or implied warranty.
                     14:  */
                     15: 
                     16: #ifndef lint
                     17: static char rcsid[] = "$Header: /sprite/src/lib/c/string/RCS/strstr.c,v 1.2 89/03/22 16:07:57 rab Exp $ SPRITE (Berkeley)";
                     18: #endif /* not lint */
                     19: 
                     20: /*
                     21:  *----------------------------------------------------------------------
                     22:  *
                     23:  * strstr --
                     24:  *
                     25:  *     Locate the first instance of a substring in a string.
                     26:  *
                     27:  * Results:
                     28:  *     If string contains substring, the return value is the
                     29:  *     location of the first matching instance of substring
                     30:  *     in string.  If string doesn't contain substring, the
                     31:  *     return value is 0.  Matching is done on an exact
                     32:  *     character-for-character basis with no wildcards or special
                     33:  *     characters.
                     34:  *
                     35:  * Side effects:
                     36:  *     None.
                     37:  *
                     38:  *----------------------------------------------------------------------
                     39:  */
                     40: 
                     41: char *
                     42: strstr(string, substring)
                     43:     register char *string;     /* String to search. */
                     44:     char *substring;           /* Substring to try to find in string. */
                     45: {
                     46:     register char *a, *b;
                     47: 
                     48:     /* First scan quickly through the two strings looking for a
                     49:      * single-character match.  When it's found, then compare the
                     50:      * rest of the substring.
                     51:      */
                     52: 
                     53:     b = substring;
                     54:     if (*b == 0) {
                     55:        return string;
                     56:     }
                     57:     for ( ; *string != 0; string += 1) {
                     58:        if (*string != *b) {
                     59:            continue;
                     60:        }
                     61:        a = string;
                     62:        while (1) {
                     63:            if (*b == 0) {
                     64:                return string;
                     65:            }
                     66:            if (*a++ != *b++) {
                     67:                break;
                     68:            }
                     69:        }
                     70:        b = substring;
                     71:     }
                     72:     return (char *) 0;
                     73: }

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