42 lines
1.3 KiB
C
42 lines
1.3 KiB
C
/*
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* Copyright (c) 2011, 2012 Jonas 'Sortie' Termansen.
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*
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* string/strstr.c
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* Locate a substring.
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*/
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#include <stdbool.h>
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#include <string.h>
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// TODO: This simple and hacky implementation runs in O(N^2) even though this
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// problem can be solved in O(N).
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char* strstr(const char* haystack, const char* needle)
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{
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if ( !needle[0] )
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return (char*) haystack;
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for ( size_t i = 0; haystack[i]; i++ )
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{
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bool diff = false;
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for ( size_t j = 0; needle[j]; j++ )
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{
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if ( haystack[i+j] != needle[j] ) { diff = true; break; }
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}
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if ( diff )
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continue;
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return (char*) haystack + i;
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}
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return NULL;
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}
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