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113 lines
2.8 KiB
C
113 lines
2.8 KiB
C
/* $xMach: strnsubst.c,v 1.3 2002/02/23 02:10:24 jmallett Exp $ */
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/*
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* Copyright (c) 2002 J. Mallett. All rights reserved.
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* You may do whatever you want with this file as long as
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* the above copyright and this notice remain intact, along
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* with the following statement:
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* For the man who taught me vi, and who got too old, too young.
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*/
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#include <sys/cdefs.h>
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#include <err.h>
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#include <stdbool.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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bool strnsubst(char **, const char *, const char *, size_t);
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/*
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* Replaces str with a string consisting of str with match replaced with
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* replstr as many times as can be done before the constructed string is
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* maxsize bytes large. It does not free the string pointed to by str, it
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* is up to the calling program to be sure that the original contents of
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* str as well as the new contents are handled in an appropriate manner.
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* If replstr is NULL, then that internally is changed to a nil-string, so
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* that we can still pretend to do somewhat meaningful substitution.
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*
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* Returns true if truncation was needed to do the replacement, false if
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* truncation was not required.
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*/
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bool
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strnsubst(char **str, const char *match, const char *replstr, size_t maxsize)
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{
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char *s1, *s2, *this;
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bool error = false;
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s1 = *str;
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if (s1 == NULL)
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return false;
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/*
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* If maxsize is 0 then set it to the length of s1, because we have
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* to duplicate s1. XXX we maybe should double-check whether the match
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* appears in s1. If it doesn't, then we also have to set the length
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* to the length of s1, to avoid modifying the argument. It may make
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* sense to check if maxsize is <= strlen(s1), because in that case we
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* want to return the unmodified string, too.
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*/
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if (maxsize == 0) {
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match = NULL;
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maxsize = strlen(s1) + 1;
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}
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s2 = calloc(1, maxsize);
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if (s2 == NULL)
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err(1, "calloc");
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if (replstr == NULL)
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replstr = "";
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if (match == NULL || replstr == NULL || maxsize == strlen(s1)) {
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strlcpy(s2, s1, maxsize);
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goto done;
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}
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for (;;) {
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this = strstr(s1, match);
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if (this == NULL)
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break;
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if ((strlen(s2) + strlen(s1) + strlen(replstr) -
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strlen(match) + 1) > maxsize) {
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strlcat(s2, s1, maxsize);
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error = true;
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goto done;
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}
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strncat(s2, s1, (uintptr_t)this - (uintptr_t)s1);
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strcat(s2, replstr);
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s1 = this + strlen(match);
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}
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strcat(s2, s1);
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done:
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*str = s2;
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return error;
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}
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#ifdef TEST
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#include <stdio.h>
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int
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main(void)
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{
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char *x, *y, *z, *za;
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x = "{}%$";
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strnsubst(&x, "%$", "{} enpury!", 255);
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y = x;
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strnsubst(&y, "}{}", "ybir", 255);
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z = y;
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strnsubst(&z, "{", "v ", 255);
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za = z;
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strnsubst(&z, NULL, za, 255);
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if (strcmp(z, "v ybir enpury!") == 0)
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printf("strnsubst() seems to work!\n");
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else
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printf("strnsubst() is broken.\n");
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printf("%s\n", z);
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free(x);
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free(y);
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free(z);
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free(za);
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return 0;
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}
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#endif
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