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fuzzyfs.c
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fuzzyfs.c
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/*
* fuzzyfs: Case-insensitive FUSE file system
* Copyright (C) 2020 Joel Puig Rubio <joel.puig.rubio@gmail.com>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
#define FUSE_USE_VERSION 26
#define TRUE 1
#define FALSE 0
#include <assert.h>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <fuse.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <sys/stat.h>
#include <unistd.h>
static const char *DOT = ".";
const char *root = NULL;
/*
* If the requested path is '/', returns a pointer to the static DOT.
* If the requested path starts with '/', increments the pointer past
* the slash and returns the incremented pointer.
* Leaves the string otherwise untouched.
* Does not allocate any memory.
*/
const char *fix_path(const char *path)
{
const char *p = path;
if (p[0] == '/')
{
if (p[1] == '\0')
return DOT;
p++;
}
return p;
}
/* Get the correct case for a file path by searching case-insenitively for matches.
* Input: path - a string holding the path that you want to correct the case of.
* This will iterate over slash-delimited chunks of path. On each iteration, it corrects
* the case of the current chunk (if correction is needed) by looking for files in the
* current chunk's parent directory (constructed from previous case-corrected chunks) that
* case-insensitively match the current chunk. If one is found, the current chunk is corrected.
* This repeats until the entire path is case-corrected. The case-corrected path is returned.
*
* A note on memory management: this allocates new memory for the return value if it succeeds.
* If it fails, it will free all the memory that it allocated.
*/
char *fix_path_case(const char *path)
{
char *p;
DIR *dp;
struct dirent *de;
struct stat s = { 0 };
int len, found;
char *token, *parent, *saveptr;
p = strdup(path);
token = strtok_r(p, "/", &saveptr);
while (token != NULL)
{
len = token - p;
if (len)
*(token - 1) = '/'; // restore delimiter
// If the current capitalization of the path (up to the current chunk) is incorrect,
// (that is, if getting info about the currently-specified chunk returns a nonzero exit code)
// Remember, strtok_r will place a null terminator after the current chunk, so we're not
// doing the whole path, just from the string beginning to the null terminator.
if (lstat(p, &s))
{
if (len)
{
// Note: this allocates new memory!
parent = (char*)malloc(len + 1);
strncpy(parent, p, len);
parent[len] = '\0';
}
else
{
// Note: allocates new memory.
parent = strdup(DOT);
}
dp = opendir(parent);
if (dp == NULL)
{
free(p);
p = NULL;
free(parent);
parent = NULL;
return NULL;
}
found = FALSE;
// Note: don't free de. It's managed separately.
while ((de = readdir(dp)) != NULL)
{
if (strcasecmp(de->d_name, token) == 0)
{
printf("%s --> %s\n", token, de->d_name);
strcpy(token, de->d_name);
found = TRUE;
break;
}
}
closedir(dp);
// parent isn't needed anymore.
free(parent);
parent = NULL;
if (!found)
{
free(p);
p = NULL;
return NULL;
}
}
token = strtok_r(NULL, "/", &saveptr);
}
return p;
}
// Gets file attributes, correcting the path's capitalization if needed.
static int fuzzyfs_getattr(const char *path, struct stat *stbuf)
{
int res;
char *p;
p = (char*)fix_path(path);
res = lstat(p, stbuf);
if (!res)
return 0;
if (errno != ENOENT)
return -errno;
// Note: this allocates new memory for p, unless it returns an error.
if (!(p = fix_path_case(p)))
return -ENOENT;
res = lstat(p, stbuf);
free(p);
p = NULL;
assert(res != -1);
return 0;
}
// Open a directory stream and put it in fi->fh.
static int fuzzyfs_opendir(const char *path, struct fuse_file_info *fi)
{
DIR *dp;
char *p;
p = (char*)fix_path(path);
dp = opendir(p);
if (dp == NULL)
{
if (errno != ENOENT)
return -errno;
// Note: allocates new memory for p.
if (!(p = fix_path_case(p)))
return -ENOENT;
dp = opendir(p);
// fix_path_case allocated new memory. Free it.
free(p);
p = NULL;
}
// fi->fh is a uint64_t, so we must cast. Casting directly to uint64_t
// generates a compiler warning, so we use uintptr_t.
fi->fh = (uintptr_t) dp;
assert(dp != NULL);
return 0;
}
// Reads the contents of a directory.
static int fuzzyfs_readdir(const char *path, void *buf, fuse_fill_dir_t filler,
off_t offset, struct fuse_file_info *fi)
{
(void) path;
(void) offset;
struct dirent *de;
// Including an intermediate unitptr_t cast avoids a compiler warning.
while ((de = readdir((DIR*)(uintptr_t)fi->fh)) != NULL)
{
struct stat st;
memset(&st, 0, sizeof(st));
st.st_ino = de->d_ino;
st.st_mode = de->d_type << 12;
if (filler(buf, de->d_name, &st, 0))
break;
}
return 0;
}
// Close the directory stream pointed to by fi->fh.
static int fuzzyfs_releasedir(const char *path, struct fuse_file_info *fi)
{
(void) path;
int res;
// Including an intermediate unitptr_t cast avoids a compiler warning.
res = closedir((DIR*)(uintptr_t)fi->fh);
if (res == -1)
res = -errno;
return res;
}
// Open a file handle and put it in fi->fh.
static int fuzzyfs_open(const char *path, struct fuse_file_info *fi)
{
int res;
char *p;
p = (char*)fix_path(path);
res = open(p, fi->flags);
if (res != -1)
{
fi->fh = res;
return 0;
}
if (errno != ENOENT)
return -errno;
// Allocates new memory for p.
if (!(p = fix_path_case(p)))
return -ENOENT;
res = open(p, fi->flags);
free(p);
p = NULL;
fi->fh = res;
assert(res != -1);
return 0;
}
// Read size bytes from the given file descriptor into the buffer buf, beginning offset bytes into the file.
static int fuzzyfs_read(const char *path, char *buf, size_t size, off_t offset,
struct fuse_file_info *fi)
{
(void) path;
int res;
res = pread(fi->fh, buf, size, offset);
if (res == -1)
res = -errno;
return res;
}
// Close the file descriptor.
static int fuzzyfs_release(const char *path, struct fuse_file_info *fi)
{
(void) path;
int res;
res = close(fi->fh);
if (res == -1)
res = -errno;
return res;
}
/*
* A function called at the filesystem startup.
* Changes directory to the first argument (the source) so that
* we can assume that the source is '.', instead of doing nasty
* directory-symlink appending.
*/
static void *fuzzyfs_init(struct fuse_conn_info *conn)
{
// cd into the root directory, wherever that is.
if (chdir(root) == -1)
{
perror("chdir");
exit(1);
}
return NULL;
}
// Parse the arguments. Notably, sets root to the first argument (the source).
static int fuzzyfs_opt_parse(void *data, const char *arg, int key,
struct fuse_args *outargs)
{
// Note: this will be triggered only by the first argument.
if (!root && key == FUSE_OPT_KEY_NONOPT)
{
// when fuse starts, it changes the workdir to the root
// so we must resolve relative paths beforehand
if (!(root = realpath(arg, NULL)))
{
perror(outargs->argv[0]);
exit(1);
}
return 0;
}
return 1;
}
// Setup the mapping between the fuse functions and the fuzzyfs functions.
static struct fuse_operations fuzzyfs_oper = {
.getattr = fuzzyfs_getattr,
.opendir = fuzzyfs_opendir,
.readdir = fuzzyfs_readdir,
.releasedir = fuzzyfs_releasedir,
.open = fuzzyfs_open,
.read = fuzzyfs_read,
.release = fuzzyfs_release,
.init = fuzzyfs_init,
};
int main(int argc, char *argv[])
{
struct fuse_args args = FUSE_ARGS_INIT(argc, argv);
fuse_opt_parse(&args, NULL, NULL, fuzzyfs_opt_parse);
umask(0);
return fuse_main(args.argc, args.argv, &fuzzyfs_oper, NULL);
}