example/hello_ll.c

   1 /*
   2     FUSE: Filesystem in Userspace
   3     Copyright (C) 2001-2007  Miklos Szeredi <miklos@szeredi.hu>
   4
   5     This program can be distributed under the terms of the GNU GPL.
   6     See the file COPYING.
   7
   8     gcc -Wall `pkg-config fuse --cflags --libs` hello_ll.c -o hello_ll
   9 */
  10
  11 #define FUSE_USE_VERSION 26
  12
  13 #include <fuse_lowlevel.h>
  14 #include <stdio.h>
  15 #include <stdlib.h>
  16 #include <string.h>
  17 #include <errno.h>
  18 #include <fcntl.h>
  19 #include <unistd.h>
  20 #include <assert.h>
  21
  22 static const char *hello_str = "Hello World!\n";
  23 static const char *hello_name = "hello";
  24
  25 static int hello_stat(fuse_ino_t ino, struct stat *stbuf)
  26 {
  27     stbuf->st_ino = ino;
  28     switch (ino) {
  29     case 1:
  30         stbuf->st_mode = S_IFDIR | 0755;
  31         stbuf->st_nlink = 2;
  32         break;
  33
  34     case 2:
  35         stbuf->st_mode = S_IFREG | 0444;
  36         stbuf->st_nlink = 1;
  37         stbuf->st_size = strlen(hello_str);
  38         break;
  39
  40     default:
  41         return -1;
  42     }
  43     return 0;
  44 }
  45
  46 static void hello_ll_getattr(fuse_req_t req, fuse_ino_t ino,
  47                              struct fuse_file_info *fi)
  48 {
  49     struct stat stbuf;
  50
  51     (void) fi;
  52
  53     memset(&stbuf, 0, sizeof(stbuf));
  54     if (hello_stat(ino, &stbuf) == -1)
  55         fuse_reply_err(req, ENOENT);
  56     else
  57         fuse_reply_attr(req, &stbuf, 1.0);
  58 }
  59
  60 static void hello_ll_lookup(fuse_req_t req, fuse_ino_t parent, const char *name)
  61 {
  62     struct fuse_entry_param e;
  63
  64     if (parent != 1 || strcmp(name, hello_name) != 0)
  65         fuse_reply_err(req, ENOENT);
  66     else {
  67         memset(&e, 0, sizeof(e));
  68         e.ino = 2;
  69         e.attr_timeout = 1.0;
  70         e.entry_timeout = 1.0;
  71         hello_stat(e.ino, &e.attr);
  72
  73         fuse_reply_entry(req, &e);
  74     }
  75 }
  76
  77 struct dirbuf {
  78     char *p;
  79     size_t size;
  80 };
  81
  82 static void dirbuf_add(fuse_req_t req, struct dirbuf *b, const char *name,
  83                        fuse_ino_t ino)
  84 {
  85     struct stat stbuf;
  86     size_t oldsize = b->size;
  87     b->size += fuse_add_direntry(req, NULL, 0, name, NULL, 0);
  88     b->p = (char *) realloc(b->p, b->size);
  89     memset(&stbuf, 0, sizeof(stbuf));
  90     stbuf.st_ino = ino;
  91     fuse_add_direntry(req, b->p + oldsize, b->size - oldsize, name, &stbuf,
  92                       b->size);
  93 }
  94
  95 #define min(x, y) ((x) < (y) ? (x) : (y))
  96
  97 static int reply_buf_limited(fuse_req_t req, const char *buf, size_t bufsize,
  98                              off_t off, size_t maxsize)
  99 {
 100     if (off < bufsize)
 101         return fuse_reply_buf(req, buf + off, min(bufsize - off, maxsize));
 102     else
 103         return fuse_reply_buf(req, NULL, 0);
 104 }
 105
 106 static void hello_ll_readdir(fuse_req_t req, fuse_ino_t ino, size_t size,
 107                              off_t off, struct fuse_file_info *fi)
 108 {
 109     (void) fi;
 110
 111     if (ino != 1)
 112         fuse_reply_err(req, ENOTDIR);
 113     else {
 114         struct dirbuf b;
 115
 116         memset(&b, 0, sizeof(b));
 117         dirbuf_add(req, &b, ".", 1);
 118         dirbuf_add(req, &b, "..", 1);
 119         dirbuf_add(req, &b, hello_name, 2);
 120         reply_buf_limited(req, b.p, b.size, off, size);
 121         free(b.p);
 122     }
 123 }
 124
 125 static void hello_ll_open(fuse_req_t req, fuse_ino_t ino,
 126                          struct fuse_file_info *fi)
 127 {
 128     if (ino != 2)
 129         fuse_reply_err(req, EISDIR);
 130     else if ((fi->flags & 3) != O_RDONLY)
 131         fuse_reply_err(req, EACCES);
 132     else
 133         fuse_reply_open(req, fi);
 134 }
 135
 136 static void hello_ll_read(fuse_req_t req, fuse_ino_t ino, size_t size,
 137                          off_t off, struct fuse_file_info *fi)
 138 {
 139     (void) fi;
 140
 141     assert(ino == 2);
 142     reply_buf_limited(req, hello_str, strlen(hello_str), off, size);
 143 }
 144
 145 static struct fuse_lowlevel_ops hello_ll_oper = {
 146     .lookup     = hello_ll_lookup,
 147     .getattr    = hello_ll_getattr,
 148     .readdir    = hello_ll_readdir,
 149     .open       = hello_ll_open,
 150     .read       = hello_ll_read,
 151 };
 152
 153 int main(int argc, char *argv[])
 154 {
 155     struct fuse_args args = FUSE_ARGS_INIT(argc, argv);
 156     struct fuse_chan *ch;
 157     char *mountpoint;
 158     int err = -1;
 159
 160     if (fuse_parse_cmdline(&args, &mountpoint, NULL, NULL) != -1 &&
 161         (ch = fuse_mount(mountpoint, &args)) != NULL) {
 162         struct fuse_session *se;
 163
 164         se = fuse_lowlevel_new(&args, &hello_ll_oper, sizeof(hello_ll_oper),
 165                                NULL);
 166         if (se != NULL) {
 167             if (fuse_set_signal_handlers(se) != -1) {
 168                 fuse_session_add_chan(se, ch);
 169                 err = fuse_session_loop(se);
 170                 fuse_remove_signal_handlers(se);
 171                 fuse_session_remove_chan(ch);
 172             }
 173             fuse_session_destroy(se);
 174         }
 175         fuse_unmount(mountpoint, ch);
 176     }
 177     fuse_opt_free_args(&args);
 178
 179     return err ? 1 : 0;
 180 }