[BCC'd to -hackers for additional comments.]
Hello,
I would appreciate comments/reviews of the following new addition to
libc. It is largely based off the current strstr(3) implementation.
Patch attached and also available at:
http://people.FreeBSD.org/~mike/patches/strnstr.diff
Best regards,
Mike Barcroft
strnstr.diff
Add a new libc function, strnstr(3), which allows one to limit the
number of characters that are searched. This is especially useful
with file operations and non-NUL terminated strings.
Index: lib/libc/string/Makefile.inc
===================================================================
RCS file: /cvs/src/lib/libc/string/Makefile.inc,v
retrieving revision 1.23
diff -u -r1.23 Makefile.inc
--- lib/libc/string/Makefile.inc 31 Jul 2001 16:34:52 -0000 1.23
+++ lib/libc/string/Makefile.inc 5 Oct 2001 00:30:43 -0000
@@ -10,6 +10,7 @@
memcpy.c memmove.c memset.c rindex.c strcasecmp.c strcat.c strchr.c \
strcmp.c strcoll.c strcpy.c strcspn.c strdup.c strerror.c \
strlcat.c strlcpy.c strlen.c strmode.c strncat.c strncmp.c strncpy.c \
+ strnstr.c \
strpbrk.c strrchr.c strsep.c strsignal.c strspn.c strstr.c strtok.c \
strxfrm.c swab.c wcscat.c wcschr.c wcscmp.c wcscpy.c wcscspn.c \
wcslcat.c wcslcpy.c wcslen.c wcsncat.c wcsncmp.c wcsncpy.c wcspbrk.c \
@@ -36,6 +37,7 @@
MLINKS+=strerror.3 perror.3 strerror.3 sys_errlist.3 strerror.3 sys_nerr.3
MLINKS+=strlcpy.3 strlcat.3
MLINKS+=strtok.3 strtok_r.3
+MLINKS+=strstr.3 strnstr.3
MLINKS+=wmemchr.3 wmemcmp.3 wmemchr.3 wmemcpy.3 \
wmemchr.3 wmemmove.3 wmemchr.3 wmemset.3 \
wmemchr.3 wcscat.3 wmemchr.3 wcschr.3 \
--- /dev/null Thu Oct 4 21:11:00 2001
+++ lib/libc/string/strnstr.c Thu Oct 4 20:37:01 2001
@@ -0,0 +1,70 @@
+/*-
+ * Copyright (c) 2001 Mike Barcroft <[EMAIL PROTECTED]>
+ * Copyright (c) 1990, 1993
+ * The Regents of the University of California. All rights reserved.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * Chris Torek.
+ *
+ * Redistribution and use in 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 in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ * 3. All advertising materials mentioning features or use of this software
+ * must display the following acknowledgement:
+ * This product includes software developed by the University of
+ * California, Berkeley and its contributors.
+ * 4. Neither the name of the University 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 REGENTS 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 REGENTS 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.
+ */
+
+#include <sys/cdefs.h>
+__RCSID("@(#)strstr.c 8.1 (Berkeley) 6/4/93");
+__FBSDID("$FreeBSD$");
+
+#include <string.h>
+
+/*
+ * Find the first occurrence of find in s, where the search is limited to the
+ * first slen characters of s.
+ */
+char *
+strnstr(s, find, slen)
+ const char *s;
+ const char *find;
+ size_t slen;
+{
+ char c, sc;
+ size_t len;
+
+ if ((c = *find++) != '\0') {
+ len = strlen(find);
+ do {
+ do {
+ if ((sc = *s++) == '\0' || slen-- < 1)
+ return (NULL);
+ } while (sc != c);
+ if (len > slen)
+ return (NULL);
+ } while (strncmp(s, find, len) != 0);
+ s--;
+ }
+ return ((char *)s);
+}
Index: lib/libc/string/strstr.3
===================================================================
RCS file: /cvs/src/lib/libc/string/strstr.3,v
retrieving revision 1.7
diff -u -r1.7 strstr.3
--- lib/libc/string/strstr.3 1 Oct 2001 16:09:00 -0000 1.7
+++ lib/libc/string/strstr.3 5 Oct 2001 01:18:13 -0000
@@ -1,3 +1,4 @@
+.\" Copyright (c) 2001 Mike Barcroft <[EMAIL PROTECTED]>
.\" Copyright (c) 1990, 1991, 1993
.\" The Regents of the University of California. All rights reserved.
.\"
@@ -40,7 +41,7 @@
.Dt STRSTR 3
.Os
.Sh NAME
-.Nm strstr
+.Nm strstr , strnstr
.Nd locate a substring in a string
.Sh LIBRARY
.Lb libc
@@ -48,6 +49,8 @@
.In string.h
.Ft char *
.Fn strstr "const char *big" "const char *little"
+.Ft char *
+.Fn strnstr "const char *big" "const char *little" "size_t len"
.Sh DESCRIPTION
The
.Fn strstr
@@ -56,22 +59,58 @@
.Fa little
in the null-terminated string
.Fa big .
+.Pp
+The
+.Fn strnstr
+function
+locates the first occurrence of the null-terminated string
+.Fa little
+in the string
+.Fa big ,
+where only the first number of characters, identified by
+.Fa len ,
+are searched.
+.Sh RETURN VALUES
If
.Fa little
-is the empty string,
-.Fn strstr
-returns
-.Fa big ;
+is an empty string,
+.Fa big
+is returned;
if
.Fa little
occurs nowhere in
.Fa big ,
-.Fn strstr
-returns NULL;
-otherwise
-.Fn strstr
-returns a pointer to the first character of the first occurrence of
-.Fa little .
+NULL is returned;
+otherwise a pointer to the first character of the first occurrence of
+.Fa little
+is returned.
+.Sh EXAMPLES
+The following sets the pointer
+.Va ptr
+to the
+.Dq Li Bar Baz
+portion of
+.Va largestring :
+.Bd -literal -offset indent
+const char *largestring = "Foo Bar Baz";
+const char *smallstring = "Bar";
+char *ptr;
+
+ptr = strstr(largestring, smallstring);
+.Ed
+.Pp
+The following sets the pointer
+.Va ptr
+to NULL, because only the first 4 characters of
+.Va largestring
+are searched:
+.Bd -literal -offset indent
+const char *largestring = "Foo Bar Baz";
+const char *smallstring = "Bar";
+char *ptr;
+
+ptr = strnstr(largestring, smallstring, 4);
+.Ed
.Sh SEE ALSO
.Xr memchr 3 ,
.Xr strchr 3 ,
Index: include/string.h
===================================================================
RCS file: /cvs/src/include/string.h,v
retrieving revision 1.6
diff -u -r1.6 string.h
--- include/string.h 16 Aug 1999 06:53:13 -0000 1.6
+++ include/string.h 5 Oct 2001 00:34:03 -0000
@@ -87,6 +87,7 @@
size_t strlcpy __P((char *, const char *, size_t));
void strmode __P((int, char *));
int strncasecmp __P((const char *, const char *, size_t));
+char *strnstr __P((const char *, const char *, size_t));
char *strsep __P((char **, const char *));
char *strsignal __P((int));
char *strtok_r __P((char *, const char *, char **));
