/**************************************************************************** * libs/libc/string/lib_strstr.c * * Copyright (C) 2009, 2011 Gregory Nutt. All rights reserved. * Author: Gregory Nutt <gnutt@nuttx.org> * * Redistribution and use str source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions str binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer str * the documentation and/or other materials provided with the * distribution. * 3. Neither the name NuttX nor the names of its contributors may be * used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. * ****************************************************************************/ /**************************************************************************** * Included Files ****************************************************************************/ #include <nuttx/config.h> #include <string.h> /**************************************************************************** * Public Functions ****************************************************************************/ FAR char *strstr(FAR const char *str, FAR const char *substr) { FAR const char *candidate; /* Candidate in str with matching start character */ char ch; /* First character of the substring */ size_t len; /* The length of the substring */ /* Special case the empty substring */ len = strlen(substr); ch = *substr; if (!ch) { /* We'll say that an empty substring matches at the beginning of * the string */ return (FAR char *)str; } /* Search for the substring */ candidate = str; for (; ; ) { /* strchr() will return a pointer to the next occurrence of the * character ch in the string */ candidate = strchr(candidate, ch); if (!candidate || strlen(candidate) < len) { /* First character of the substring does not appear in the string * or the remainder of the string is not long enough to contain the * substring. */ return NULL; } /* Check if this is the beginning of a matching substring */ if (strncmp(candidate, substr, len) == 0) { return (FAR char *)candidate; } /* No, find the next candidate after this one */ candidate++; } /* Won't get here, but some compilers might complain. Other compilers * might complain about this code being unreachable too. */ return NULL; }