libblkid/at.c

/*
 * Portable xxxat() functions.
 *
 * No copyright is claimed.  This code is in the public domain; do with
 * it what you wish.
 *
 * Written by Karel Zak <kzak@redhat.com>
 */
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/stat.h>

#include "at.h"
#include "c.h"

#ifdef HAVE_FSTATAT
int fstat_at(int dir, const char *dirname __attribute__ ((__unused__)),
	     const char *filename, struct stat *st, int nofollow)
{
	return fstatat(dir, filename, st,
			nofollow ? AT_SYMLINK_NOFOLLOW : 0);
}
#else
int fstat_at(int dir, const char *dirname, const char *filename,
				struct stat *st, int nofollow)
{

	if (*filename != '/') {
		char path[PATH_MAX];
		int len;

		len = snprintf(path, sizeof(path), "%s/%s", dirname, filename);
		if (len < 0 || len + 1 > sizeof(path))
			return -1;

		return nofollow ? lstat(path, st) : stat(path, st);
	}

	return nofollow ? lstat(filename, st) : stat(filename, st);
}
#endif

#ifdef HAVE_FSTATAT
int open_at(int dir, const char *dirname __attribute__ ((__unused__)),
	    const char *filename, int flags)
{
	return openat(dir, filename, flags);
}
#else
int open_at(int dir, const char *dirname, const char *filename, int flags)
{
	if (*filename != '/') {
		char path[PATH_MAX];
		int len;

		len = snprintf(path, sizeof(path), "%s/%s", dirname, filename);
		if (len < 0 || len + 1 > sizeof(path))
			return -1;

		return open(path, flags);
	}
	return open(filename, flags);
}
#endif

FILE *fopen_at(int dir, const char *dirname, const char *filename, int flags,
			const char *mode)
{
	int fd = open_at(dir, dirname, filename, flags);

	if (fd < 0)
		return NULL;

	return fdopen(fd, mode);
}

#ifdef HAVE_FSTATAT
ssize_t readlink_at(int dir, const char *dirname __attribute__ ((__unused__)),
		    const char *pathname, char *buf, size_t bufsiz)
{
	return readlinkat(dir, pathname, buf, bufsiz);
}
#else
ssize_t readlink_at(int dir, const char *dirname, const char *pathname,
		    char *buf, size_t bufsiz)
{
	if (*pathname != '/') {
		char path[PATH_MAX];
		int len;

		len = snprintf(path, sizeof(path), "%s/%s", dirname, pathname);
		if (len < 0 || len + 1 > sizeof(path))
			return -1;

		return readlink(path, buf, bufsiz);
	}
	return readlink(pathname, buf, bufsiz);
}
#endif

#ifdef TEST_PROGRAM_AT
#include <errno.h>
#include <sys/types.h>
#include <dirent.h>
#include <string.h>

int main(int argc, char *argv[])
{
	DIR *dir;
	struct dirent *d;
	char *dirname;

	if (argc != 2) {
		fprintf(stderr, "usage: %s <directory>\n", argv[0]);
		exit(EXIT_FAILURE);
	}
	dirname = argv[1];

	dir = opendir(dirname);
	if (!dir)
		err(EXIT_FAILURE, "cannot open %s", dirname);

	while ((d = readdir(dir))) {
		struct stat st;
		FILE *f;

		printf("%32s ", d->d_name);

		if (fstat_at(dirfd(dir), dirname, d->d_name, &st, 0) == 0)
			printf("%16jd bytes ", st.st_size);
		else
			printf("%16s bytes ", "???");

		f = fopen_at(dirfd(dir), dirname, d->d_name, O_RDONLY, "r");
		printf("   %s\n", f ? "OK" : strerror(errno));
		if (f)
			fclose(f);
	}
	closedir(dir);
	return EXIT_SUCCESS;
}
#endif