112 lines
2.2 KiB
C
112 lines
2.2 KiB
C
/*
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strcasestr -- case insensitive substring searching function.
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*/
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/*
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Copyright 2019-2021 James R.
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All rights reserved.
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Redistribution and use in source forms, with or without modification, is
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permitted provided that the following condition is met:
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1. Redistributions of source code must retain the above copyright notice, this
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condition and the following disclaimer.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
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ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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static inline int
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trycmp (char **pp, char *cp,
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const char *q, size_t qn)
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{
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char *p;
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p = (*pp);
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if (strncasecmp(p, q, qn) == 0)
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return 0;
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(*pp) = strchr(&p[1], (*cp));
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return 1;
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}
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static inline void
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swapp (char ***ppap, char ***ppbp, char **cpap, char **cpbp)
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{
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char **pp;
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char *p;
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pp = *ppap;
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*ppap = *ppbp;
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*ppbp = pp;
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p = *cpap;
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*cpap = *cpbp;
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*cpbp = p;
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}
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char *
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strcasestr (const char *s, const char *q)
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{
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size_t qn;
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char uc;
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char lc;
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char *up;
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char *lp;
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char **ppa;
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char **ppb;
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char *cpa;
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char *cpb;
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uc = toupper(*q);
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lc = tolower(*q);
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up = strchr(s, uc);
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lp = strchr(s, lc);
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if (!( (intptr_t)up|(intptr_t)lp ))
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return 0;
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if (!lp || ( up && up < lp ))
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{
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ppa = &up;
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ppb = &lp;
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cpa = &uc;
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cpb = &lc;
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}
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else
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{
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ppa = &lp;
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ppb = &up;
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cpa = &lc;
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cpb = &uc;
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}
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qn = strlen(q);
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for (;;)
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{
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if (trycmp(ppa, cpa, q, qn) == 0)
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return (*ppa);
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if (!( (intptr_t)up|(intptr_t)lp ))
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break;
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if (!(*ppa) || ( (*ppb) && (*ppb) < (*ppa) ))
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swapp(&ppa, &ppb, &cpa, &cpb);
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}
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return 0;
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}
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