freebsd-dev/lib/libc/gen/dirname.c
Ed Schouten e2f6816100 Reimplement dirname(3) to be thread-safe.
Now that we've updated the prototypes of the basename(3) and dirname(3)
functions to conform to POSIX, let's go ahead and reimplement dirname(3)
in such a way that it's thread-safe, but also guaranteed to succeed. C
libraries like glibc, musl and the one that's part of Solaris already
follow such an approach.

Move the existing implementation to another source file,
freebsd11_dirname.c to keep existing users of the API that pass in a
constant string happy, using symbol versioning.

Put a new version of the function in dirname.c, obtained from CloudABI's
C library. This version scans through the pathname string from left to
right, normalizing it, while discarding the last pathname component.

Reviewed by:	emaste, jilles
Differential Revision:	https://reviews.freebsd.org/D7355
2016-08-12 07:03:58 +00:00

91 lines
2.6 KiB
C

/*-
* Copyright (c) 2015-2016 Nuxi, https://nuxi.nl/
*
* 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.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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>
__FBSDID("$FreeBSD$");
#include <libgen.h>
#include <stdbool.h>
#include <string.h>
char *
dirname(char *path)
{
const char *in, *prev, *begin, *end;
char *out;
size_t prevlen;
bool skipslash;
/*
* If path is a null pointer or points to an empty string,
* dirname() shall return a pointer to the string ".".
*/
if (path == NULL || *path == '\0')
return ((char *)".");
/* Retain at least one leading slash character. */
in = out = *path == '/' ? path + 1 : path;
skipslash = true;
prev = ".";
prevlen = 1;
for (;;) {
/* Extract the next pathname component. */
while (*in == '/')
++in;
begin = in;
while (*in != '/' && *in != '\0')
++in;
end = in;
if (begin == end)
break;
/*
* Copy over the previous pathname component, except if
* it's dot. There is no point in retaining those.
*/
if (prevlen != 1 || *prev != '.') {
if (!skipslash)
*out++ = '/';
skipslash = false;
memmove(out, prev, prevlen);
out += prevlen;
}
/* Preserve the pathname component for the next iteration. */
prev = begin;
prevlen = end - begin;
}
/*
* If path does not contain a '/', then dirname() shall return a
* pointer to the string ".".
*/
if (out == path)
*out++ = '.';
*out = '\0';
return (path);
}