diff options
Diffstat (limited to 'nuttx/libc/string/lib_strstr.c')
-rw-r--r-- | nuttx/libc/string/lib_strstr.c | 106 |
1 files changed, 106 insertions, 0 deletions
diff --git a/nuttx/libc/string/lib_strstr.c b/nuttx/libc/string/lib_strstr.c new file mode 100644 index 000000000..7a60a680d --- /dev/null +++ b/nuttx/libc/string/lib_strstr.c @@ -0,0 +1,106 @@ +/**************************************************************************** + * 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> + +/**************************************************************************** + * Global Functions + ****************************************************************************/ + +char *strstr(const char *str, const char *substr) +{ + const char *candidate; /* Candidate in str with matching start character */ + char ch; /* First character of the substring */ + int 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 (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 (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; +} + |