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sortix--sortix/libc/string/strstr.cpp

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/*******************************************************************************
Copyright(C) Jonas 'Sortie' Termansen 2011, 2012.
This file is part of the Sortix C Library.
The Sortix C Library is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation, either version 3 of the License, or (at your
option) any later version.
The Sortix C Library is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
License for more details.
You should have received a copy of the GNU Lesser General Public License
along with the Sortix C Library. If not, see <http://www.gnu.org/licenses/>.
string/strstr.cpp
Locate a substring.
*******************************************************************************/
#include <string.h>
// TODO: This simple and hacky implementation runs in O(N^2) even though this
// problem can be solved in O(N).
extern "C" char* strstr(const char* haystack, const char* needle)
{
if ( !needle[0] )
return (char*) haystack;
for ( size_t i = 0; haystack[i]; i++ )
{
bool diff = false;
for ( size_t j = 0; needle[j]; j++ )
{
if ( haystack[i+j] != needle[j] ) { diff = true; break; }
}
if ( diff )
continue;
return (char*) haystack + i;
}
return NULL;
}