subdir.c

UNIX/LINUX下面的用户文件系统

/*
    fuse subdir module: offset paths with a base directory
    Copyright (C) 2007  Miklos Szeredi <[e-mail]>

    This program can be distributed under the terms of the GNU LGPL.
    See the file COPYING.LIB
*/

#define FUSE_USE_VERSION 26

#include <fuse.h>
#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <string.h>
#include <errno.h>

struct subdir {
    char *base;
    size_t baselen;
    int rellinks;
    struct fuse_fs *next;
};

static struct subdir *subdir_get(void)
{
    return fuse_get_context()->private_data;
}

static char *subdir_addpath(struct subdir *d, const char *path)
{
    unsigned newlen = d->baselen + strlen(path);
    char *newpath = malloc(newlen + 2);
    if (newpath) {
        if (path[0] == '/')
            path++;
        strcpy(newpath, d->base);
        strcpy(newpath + d->baselen, path);
        if (!newpath[0])
            strcpy(newpath, ".");
    }
    return newpath;
}

static int subdir_getattr(const char *path, struct stat *stbuf)
{
    struct subdir *d = subdir_get();
    char *newpath = subdir_addpath(d, path);
    int err = -ENOMEM;
    if (newpath) {
        err = fuse_fs_getattr(d->next, newpath, stbuf);
        free(newpath);
    }
    return err;
}

static int subdir_fgetattr(const char *path, struct stat *stbuf,
                           struct fuse_file_info *fi)
{
    struct subdir *d = subdir_get();
    char *newpath = subdir_addpath(d, path);
    int err = -ENOMEM;
    if (newpath) {
        err = fuse_fs_fgetattr(d->next, newpath, stbuf, fi);
        free(newpath);
    }
    return err;
}

static int subdir_access(const char *path, int mask)
{
    struct subdir *d = subdir_get();
    char *newpath = subdir_addpath(d, path);
    int err = -ENOMEM;
    if (newpath) {
        err = fuse_fs_access(d->next, newpath, mask);
        free(newpath);
    }
    return err;
}


static int count_components(const char *p)
{
    int ctr;

    for (; *p == '/'; p++);
    for (ctr = 0; *p; ctr++) {
        for (; *p && *p != '/'; p++);
        for (; *p == '/'; p++);
    }
    return ctr;
}

static void strip_common(const char **sp, const char **tp)
{
    const char *s = *sp;
    const char *t = *tp;
    do {
        for (; *s == '/'; s++);
        for (; *t == '/'; t++);
        *tp = t;
        *sp = s;
        for (; *s == *t && *s && *s != '/'; s++, t++);
    } while ((*s == *t && *s) || (!*s && *t == '/') || (*s == '/' && !*t));
}

static void transform_symlink(struct subdir *d, const char *path,
                              char *buf, size_t size)
{
    const char *l = buf;
    size_t llen;
    char *s;
    int dotdots;
    int i;

    if (l[0] != '/' || d->base[0] != '/')
        return;

    strip_common(&l, &path);
    if (l - buf < (long) d->baselen)
        return;

    dotdots = count_components(path);
    if (!dotdots)
        return;
    dotdots--;

    llen = strlen(l);
    if (dotdots * 3 + llen + 2 > size)
        return;

    s = buf + dotdots * 3;
    if (llen)
        memmove(s, l, llen + 1);
    else if (!dotdots)
        strcpy(s, ".");
    else
        *s = '\0';

    for (s = buf, i = 0; i < dotdots; i++, s += 3)
        memcpy(s, "../", 3);
}


static int subdir_readlink(const char *path, char *buf, size_t size)
{
    struct subdir *d = subdir_get();
    char *newpath = subdir_addpath(d, path);
    int err = -ENOMEM;
    if (newpath) {
        err = fuse_fs_readlink(d->next, newpath, buf, size);
        if (!err && d->rellinks)
            transform_symlink(d, newpath, buf, size);
        free(newpath);
    }
    return err;
}

static int subdir_opendir(const char *path, struct fuse_file_info *fi)
{
    struct subdir *d = subdir_get();
    char *newpath = subdir_addpath(d, path);
    int err = -ENOMEM;
    if (newpath) {
        err = fuse_fs_opendir(d->next, newpath, fi);
        free(newpath);
    }
    return err;
}

static int subdir_readdir(const char *path, void *buf,
                          fuse_fill_dir_t filler, off_t offset,
                          struct fuse_file_info *fi)
{
    struct subdir *d = subdir_get();
    char *newpath = subdir_addpath(d, path);
    int err = -ENOMEM;
    if (newpath) {
        err = fuse_fs_readdir(d->next, newpath, buf, filler, offset, fi);
        free(newpath);
    }
    return err;
}

static int subdir_releasedir(const char *path, struct fuse_file_info *fi)
{
    struct subdir *d = subdir_get();
    char *newpath = subdir_addpath(d, path);
    int err = -ENOMEM;
    if (newpath) {
        err = fuse_fs_releasedir(d->next, newpath, fi);
        free(newpath);
    }
    return err;
}

static int subdir_mknod(const char *path, mode_t mode, dev_t rdev)
{
    struct subdir *d = subdir_get();
    char *newpath = subdir_addpath(d, path);
    int err = -ENOMEM;
    if (newpath) {
        err = fuse_fs_mknod(d->next, newpath, mode, rdev);
        free(newpath);
    }
    return err;
}

static int subdir_mkdir(const char *path, mode_t mode)
{
    struct subdir *d = subdir_get();
    char *newpath = subdir_addpath(d, path);
    int err = -ENOMEM;
    if (newpath) {
        err = fuse_fs_mkdir(d->next, newpath, mode);
        free(newpath);
    }
    return err;
}

static int subdir_unlink(const char *path)
{
    struct subdir *d = subdir_get();
    char *newpath = subdir_addpath(d, path);
    int err = -ENOMEM;
    if (newpath) {
        err = fuse_fs_unlink(d->next, newpath);
        free(newpath);
    }
    return err;
}

static int subdir_rmdir(const char *path)
{
    struct subdir *d = subdir_get();
    char *newpath = subdir_addpath(d, path);
    int err = -ENOMEM;
    if (newpath) {
        err = fuse_fs_rmdir(d->next, newpath);
        free(newpath);
    }
    return err;
}

static int subdir_symlink(const char *from, const char *path)
{
    struct subdir *d = subdir_get();
    char *newpath = subdir_addpath(d, path);
    int err = -ENOMEM;
    if (newpath) {
        err = fuse_fs_symlink(d->next, from, newpath);
        free(newpath);
    }
    return err;
}

static int subdir_rename(const char *from, const char *to)
{
    struct subdir *d = subdir_get();
    char *newfrom = subdir_addpath(d, from);
    char *newto = subdir_addpath(d, to);
    int err = -ENOMEM;
    if (newfrom && newto)
        err = fuse_fs_rename(d->next, newfrom, newto);
    free(newfrom);
    free(newto);
    return err;
}

static int subdir_link(const char *from, const char *to)
{
    struct subdir *d = subdir_get();
    char *newfrom = subdir_addpath(d, from);
    char *newto = subdir_addpath(d, to);
    int err = -ENOMEM;
    if (newfrom && newto)
        err = fuse_fs_link(d->next, newfrom, newto);
    free(newfrom);
    free(newto);
    return err;
}

static int subdir_chmod(const char *path, mode_t mode)
{
    struct subdir *d = subdir_get();
    char *newpath = subdir_addpath(d, path);
    int err = -ENOMEM;
    if (newpath) {
        err = fuse_fs_chmod(d->next, newpath, mode);
        free(newpath);
    }
    return err;
}

static int subdir_chown(const char *path, uid_t uid, gid_t gid)
{
    struct subdir *d = subdir_get();
    char *newpath = subdir_addpath(d, path);
    int err = -ENOMEM;
    if (newpath) {
        err = fuse_fs_chown(d->next, newpath, uid, gid);
        free(newpath);
    }
    return err;
}

static int subdir_truncate(const char *path, off_t size)
{
    struct subdir *d = subdir_get();
    char *newpath = subdir_addpath(d, path);
    int err = -ENOMEM;
    if (newpath) {
        err = fuse_fs_truncate(d->next, newpath, size);
        free(newpath);
    }
    return err;
}

static int subdir_ftruncate(const char *path, off_t size,
                         struct fuse_file_info *fi)
{
    struct subdir *d = subdir_get();
    char *newpath = subdir_addpath(d, path);
    int err = -ENOMEM;
    if (newpath) {
        err = fuse_fs_ftruncate(d->next, newpath, size, fi);
        free(newpath);
    }
    return err;
}