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<li class="navelem"><a class="el" href="dir_f0accbfe6ac750cea68457902814c321.html">fuse-3.10.1</a></li><li class="navelem"><a class="el" href="dir_d87d7dcf3f6118427cc93cf1ecddad64.html">example</a></li> </ul>
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<div class="textblock"><code>#include <config.h></code><br />
<code>#include <fuse.h></code><br />
<code>#include <unistd.h></code><br />
<code>#include <ctype.h></code><br />
<code>#include <string.h></code><br />
<code>#include <stdio.h></code><br />
<code>#include <stdlib.h></code><br />
<code>#include <errno.h></code><br />
<code>#include <time.h></code><br />
<code>#include <pthread.h></code><br />
<code>#include <poll.h></code><br />
</div>
<p><a href="fuse-3_810_81_2example_2poll_8c_source.html">Go to the source code of this file.</a></p>
<a name="details" id="details"></a><h2 class="groupheader">Detailed Description</h2>
<div class="textblock"><p>This example illustrates how to write a FUSE file system that supports polling for changes that don't come through the kernel. It can be tested with the poll_client.c program.</p>
<p>Compile with: </p><pre class="fragment">gcc -Wall poll.c `pkg-config fuse3 --cflags --libs` -o poll
</pre><h2>Source code</h2>
<div class="fragment"><div class="line"><span class="comment">/*</span></div><div class="line"><span class="comment"> FUSE fsel: FUSE select example</span></div><div class="line"><span class="comment"> Copyright (C) 2008 SUSE Linux Products GmbH</span></div><div class="line"><span class="comment"> Copyright (C) 2008 Tejun Heo <teheo@suse.de></span></div><div class="line"><span class="comment"></span></div><div class="line"><span class="comment"> This program can be distributed under the terms of the GNU GPLv2.</span></div><div class="line"><span class="comment"> See the file COPYING.</span></div><div class="line"><span class="comment">*/</span></div><div class="line"></div><div class="line"><span class="preprocessor">#define FUSE_USE_VERSION 31</span></div><div class="line"></div><div class="line"><span class="preprocessor">#include <config.h></span></div><div class="line"></div><div class="line"><span class="preprocessor">#include <fuse.h></span></div><div class="line"><span class="preprocessor">#include <unistd.h></span></div><div class="line"><span class="preprocessor">#include <ctype.h></span></div><div class="line"><span class="preprocessor">#include <string.h></span></div><div class="line"><span class="preprocessor">#include <stdio.h></span></div><div class="line"><span class="preprocessor">#include <stdlib.h></span></div><div class="line"><span class="preprocessor">#include <errno.h></span></div><div class="line"><span class="preprocessor">#include <time.h></span></div><div class="line"><span class="preprocessor">#include <pthread.h></span></div><div class="line"><span class="preprocessor">#include <poll.h></span></div><div class="line"></div><div class="line"><span class="comment">/*</span></div><div class="line"><span class="comment"> * fsel_open_mask is used to limit the number of opens to 1 per file.</span></div><div class="line"><span class="comment"> * This is to use file index (0-F) as fh as poll support requires</span></div><div class="line"><span class="comment"> * unique fh per open file. Lifting this would require proper open</span></div><div class="line"><span class="comment"> * file management.</span></div><div class="line"><span class="comment"> */</span></div><div class="line"><span class="keyword">static</span> <span class="keywordtype">unsigned</span> fsel_open_mask;</div><div class="line"><span class="keyword">static</span> <span class="keyword">const</span> <span class="keywordtype">char</span> fsel_hex_map[] = <span class="stringliteral">"0123456789ABCDEF"</span>;</div><div class="line"><span class="keyword">static</span> <span class="keyword">struct </span>fuse *fsel_fuse; <span class="comment">/* needed for poll notification */</span></div><div class="line"></div><div class="line"><span class="preprocessor">#define FSEL_CNT_MAX 10 </span><span class="comment">/* each file can store upto 10 chars */</span><span class="preprocessor"></span></div><div class="line"><span class="preprocessor">#define FSEL_FILES 16</span></div><div class="line"></div><div class="line"><span class="keyword">static</span> pthread_mutex_t fsel_mutex; <span class="comment">/* protects notify_mask and cnt array */</span></div><div class="line"><span class="keyword">static</span> <span class="keywordtype">unsigned</span> fsel_poll_notify_mask; <span class="comment">/* poll notification scheduled? */</span></div><div class="line"><span class="keyword">static</span> <span class="keyword">struct </span>fuse_pollhandle *fsel_poll_handle[FSEL_FILES]; <span class="comment">/* poll notify handles */</span></div><div class="line"><span class="keyword">static</span> <span class="keywordtype">unsigned</span> fsel_cnt[FSEL_FILES]; <span class="comment">/* nbytes stored in each file */</span></div><div class="line"></div><div class="line"><span class="keyword">static</span> <span class="keywordtype">int</span> fsel_path_index(<span class="keyword">const</span> <span class="keywordtype">char</span> *path)</div><div class="line">{</div><div class="line"> <span class="keywordtype">char</span> ch = path[1];</div><div class="line"></div><div class="line"> <span class="keywordflow">if</span> (strlen(path) != 2 || path[0] != <span class="charliteral">'/'</span> || !isxdigit(ch) || islower(ch))</div><div class="line"> <span class="keywordflow">return</span> -1;</div><div class="line"> <span class="keywordflow">return</span> ch <= <span class="charliteral">'9'</span> ? ch - <span class="charliteral">'0'</span> : ch - <span class="charliteral">'A'</span> + 10;</div><div class="line">}</div><div class="line"></div><div class="line"><span class="keyword">static</span> <span class="keywordtype">int</span> fsel_getattr(<span class="keyword">const</span> <span class="keywordtype">char</span> *path, <span class="keyword">struct</span> stat *stbuf,</div><div class="line"> <span class="keyword">struct</span> <a class="code" href="structfuse__file__info.html">fuse_file_info</a> *fi)</div><div class="line">{</div><div class="line"> (void) fi;</div><div class="line"> <span class="keywordtype">int</span> idx;</div><div class="line"></div><div class="line"> memset(stbuf, 0, <span class="keyword">sizeof</span>(<span class="keyword">struct</span> stat));</div><div class="line"></div><div class="line"> <span class="keywordflow">if</span> (strcmp(path, <span class="stringliteral">"/"</span>) == 0) {</div><div class="line"> stbuf->st_mode = S_IFDIR | 0555;</div><div class="line"> stbuf->st_nlink = 2;</div><div class="line"> <span class="keywordflow">return</span> 0;</div><div class="line"> }</div><div class="line"></div><div class="line"> idx = fsel_path_index(path);</div><div class="line"> <span class="keywordflow">if</span> (idx < 0)</div><div class="line"> <span class="keywordflow">return</span> -ENOENT;</div><div class="line"></div><div class="line"> stbuf->st_mode = S_IFREG | 0444;</div><div class="line"> stbuf->st_nlink = 1;</div><div class="line"> stbuf->st_size = fsel_cnt[idx];</div><div class="line"> <span class="keywordflow">return</span> 0;</div><div class="line">}</div><div class="line"></div><div class="line"><span class="keyword">static</span> <span class="keywordtype">int</span> fsel_readdir(<span class="keyword">const</span> <span class="keywordtype">char</span> *path, <span class="keywordtype">void</span> *buf, <a class="code" href="fuse-3_810_81_2include_2fuse_8h.html#a7dd132de66a5cc2add2a4eff5d435660">fuse_fill_dir_t</a> filler,</div><div class="line"> off_t offset, <span class="keyword">struct</span> <a class="code" href="structfuse__file__info.html">fuse_file_info</a> *fi,</div><div class="line"> <span class="keyword">enum</span> <a class="code" href="fuse-3_810_81_2include_2fuse_8h.html#af2bcf2a473b41b3cc8da8c079656a074">fuse_readdir_flags</a> flags)</div><div class="line">{</div><div class="line"> <span class="keywordtype">char</span> name[2] = { };</div><div class="line"> <span class="keywordtype">int</span> i;</div><div class="line"></div><div class="line"> (void) offset;</div><div class="line"> (void) fi;</div><div class="line"> (void) flags;</div><div class="line"></div><div class="line"> <span class="keywordflow">if</span> (strcmp(path, <span class="stringliteral">"/"</span>) != 0)</div><div class="line"> <span class="keywordflow">return</span> -ENOENT;</div><div class="line"></div><div class="line"> <span class="keywordflow">for</span> (i = 0; i < FSEL_FILES; i++) {</div><div class="line"> name[0] = fsel_hex_map[i];</div><div class="line"> filler(buf, name, NULL, 0, 0);</div><div class="line"> }</div><div class="line"></div><div class="line"> <span class="keywordflow">return</span> 0;</div><div class="line">}</div><div class="line"></div><div class="line"><span class="keyword">static</span> <span class="keywordtype">int</span> fsel_open(<span class="keyword">const</span> <span class="keywordtype">char</span> *path, <span class="keyword">struct</span> <a class="code" href="structfuse__file__info.html">fuse_file_info</a> *fi)</div><div class="line">{</div><div class="line"> <span class="keywordtype">int</span> idx = fsel_path_index(path);</div><div class="line"></div><div class="line"> <span class="keywordflow">if</span> (idx < 0)</div><div class="line"> <span class="keywordflow">return</span> -ENOENT;</div><div class="line"> <span class="keywordflow">if</span> ((fi-><a class="code" href="structfuse__file__info.html#ae7d31802727be19670193a411647bca5">flags</a> & O_ACCMODE) != O_RDONLY)</div><div class="line"> <span class="keywordflow">return</span> -EACCES;</div><div class="line"> <span class="keywordflow">if</span> (fsel_open_mask & (1 << idx))</div><div class="line"> <span class="keywordflow">return</span> -EBUSY;</div><div class="line"> fsel_open_mask |= (1 << idx);</div><div class="line"></div><div class="line"> <span class="comment">/*</span></div><div class="line"><span class="comment"> * fsel files are nonseekable somewhat pipe-like files which</span></div><div class="line"><span class="comment"> * gets filled up periodically by producer thread and consumed</span></div><div class="line"><span class="comment"> * on read. Tell FUSE as such.</span></div><div class="line"><span class="comment"> */</span></div><div class="line"> fi-><a class="code" href="structfuse__file__info.html#a45314d0b92a8d4c9de33d996aa59ada8">fh</a> = idx;</div><div class="line"> fi-><a class="code" href="structfuse__file__info.html#a03b59a10e62963d9affa34ad78bd144a">direct_io</a> = 1;</div><div class="line"> fi-><a class="code" href="structfuse__file__info.html#a272022c57a6a79dd8f98ef597786e154">nonseekable</a> = 1;</div><div class="line"></div><div class="line"> <span class="keywordflow">return</span> 0;</div><div class="line">}</div><div class="line"></div><div class="line"><span class="keyword">static</span> <span class="keywordtype">int</span> fsel_release(<span class="keyword">const</span> <span class="keywordtype">char</span> *path, <span class="keyword">struct</span> <a class="code" href="structfuse__file__info.html">fuse_file_info</a> *fi)</div><div class="line">{</div><div class="line"> <span class="keywordtype">int</span> idx = fi-><a class="code" href="structfuse__file__info.html#a45314d0b92a8d4c9de33d996aa59ada8">fh</a>;</div><div class="line"></div><div class="line"> (void) path;</div><div class="line"></div><div class="line"> fsel_open_mask &= ~(1 << idx);</div><div class="line"> <span class="keywordflow">return</span> 0;</div><div class="line">}</div><div class="line"></div><div class="line"><span class="keyword">static</span> <span class="keywordtype">int</span> fsel_read(<span class="keyword">const</span> <span class="keywordtype">char</span> *path, <span class="keywordtype">char</span> *buf, <span class="keywordtype">size_t</span> size, off_t offset,</div><div class="line"> <span class="keyword">struct</span> <a class="code" href="structfuse__file__info.html">fuse_file_info</a> *fi)</div><div class="line">{</div><div class="line"> <span class="keywordtype">int</span> idx = fi-><a class="code" href="structfuse__file__info.html#a45314d0b92a8d4c9de33d996aa59ada8">fh</a>;</div><div class="line"></div><div class="line"> (void) path;</div><div class="line"> (void) offset;</div><div class="line"></div><div class="line"> pthread_mutex_lock(&fsel_mutex);</div><div class="line"> <span class="keywordflow">if</span> (fsel_cnt[idx] < size)</div><div class="line"> size = fsel_cnt[idx];</div><div class="line"> printf(<span class="stringliteral">"READ %X transferred=%zu cnt=%u\n"</span>, idx, size, fsel_cnt[idx]);</div><div class="line"> fsel_cnt[idx] -= size;</div><div class="line"> pthread_mutex_unlock(&fsel_mutex);</div><div class="line"></div><div class="line"> memset(buf, fsel_hex_map[idx], size);</div><div class="line"> <span class="keywordflow">return</span> size;</div><div class="line">}</div><div class="line"></div><div class="line"><span class="keyword">static</span> <span class="keywordtype">int</span> fsel_poll(<span class="keyword">const</span> <span class="keywordtype">char</span> *path, <span class="keyword">struct</span> <a class="code" href="structfuse__file__info.html">fuse_file_info</a> *fi,</div><div class="line"> <span class="keyword">struct</span> fuse_pollhandle *ph, <span class="keywordtype">unsigned</span> *reventsp)</div><div class="line">{</div><div class="line"> <span class="keyword">static</span> <span class="keywordtype">unsigned</span> polled_zero;</div><div class="line"> <span class="keywordtype">int</span> idx = fi-><a class="code" href="structfuse__file__info.html#a45314d0b92a8d4c9de33d996aa59ada8">fh</a>;</div><div class="line"></div><div class="line"> (void) path;</div><div class="line"></div><div class="line"> <span class="comment">/*</span></div><div class="line"><span class="comment"> * Poll notification requires pointer to struct fuse which</span></div><div class="line"><span class="comment"> * can't be obtained when using fuse_main(). As notification</span></div><div class="line"><span class="comment"> * happens only after poll is called, fill it here from</span></div><div class="line"><span class="comment"> * fuse_context.</span></div><div class="line"><span class="comment"> */</span></div><div class="line"> <span class="keywordflow">if</span> (!fsel_fuse) {</div><div class="line"> <span class="keyword">struct </span><a class="code" href="structfuse__context.html">fuse_context</a> *cxt = <a class="code" href="fuse-3_810_81_2include_2fuse_8h.html#a9a0f2a6603cb1e21f5e4c1aec84a3bcc">fuse_get_context</a>();</div><div class="line"> <span class="keywordflow">if</span> (cxt)</div><div class="line"> fsel_fuse = cxt-><a class="code" href="structfuse__context.html#a9f2163e75f0333774a43b6c770253e8d">fuse</a>;</div><div class="line"> }</div><div class="line"></div><div class="line"> pthread_mutex_lock(&fsel_mutex);</div><div class="line"></div><div class="line"> <span class="keywordflow">if</span> (ph != NULL) {</div><div class="line"> <span class="keyword">struct </span>fuse_pollhandle *oldph = fsel_poll_handle[idx];</div><div class="line"></div><div class="line"> <span class="keywordflow">if</span> (oldph)</div><div class="line"> <a class="code" href="fuse-3_810_81_2include_2fuse__common_8h.html#adf5027f8a38b2efc03858efd7fdc756a">fuse_pollhandle_destroy</a>(oldph);</div><div class="line"></div><div class="line"> fsel_poll_notify_mask |= (1 << idx);</div><div class="line"> fsel_poll_handle[idx] = ph;</div><div class="line"> }</div><div class="line"></div><div class="line"> <span class="keywordflow">if</span> (fsel_cnt[idx]) {</div><div class="line"> *reventsp |= POLLIN;</div><div class="line"> printf(<span class="stringliteral">"POLL %X cnt=%u polled_zero=%u\n"</span>,</div><div class="line"> idx, fsel_cnt[idx], polled_zero);</div><div class="line"> polled_zero = 0;</div><div class="line"> } <span class="keywordflow">else</span></div><div class="line"> polled_zero++;</div><div class="line"></div><div class="line"> pthread_mutex_unlock(&fsel_mutex);</div><div class="line"> <span class="keywordflow">return</span> 0;</div><div class="line">}</div><div class="line"></div><div class="line"><span class="keyword">static</span> <span class="keyword">const</span> <span class="keyword">struct </span><a class="code" href="structfuse__operations.html">fuse_operations</a> fsel_oper = {</div><div class="line"> .<a class="code" href="structfuse__operations.html#a60144dbd1a893008d9112e949300eb77">getattr</a> = fsel_getattr,</div><div class="line"> .readdir = fsel_readdir,</div><div class="line"> .open = fsel_open,</div><div class="line"> .release = fsel_release,</div><div class="line"> .read = fsel_read,</div><div class="line"> .poll = fsel_poll,</div><div class="line">};</div><div class="line"></div><div class="line"><span class="keyword">static</span> <span class="keywordtype">void</span> *fsel_producer(<span class="keywordtype">void</span> *data)</div><div class="line">{</div><div class="line"> <span class="keyword">const</span> <span class="keyword">struct </span>timespec interval = { 0, 250000000 };</div><div class="line"> <span class="keywordtype">unsigned</span> idx = 0, nr = 1;</div><div class="line"></div><div class="line"> (void) data;</div><div class="line"></div><div class="line"> <span class="keywordflow">while</span> (1) {</div><div class="line"> <span class="keywordtype">int</span> i, t;</div><div class="line"></div><div class="line"> pthread_mutex_lock(&fsel_mutex);</div><div class="line"></div><div class="line"> <span class="comment">/*</span></div><div class="line"><span class="comment"> * This is the main producer loop which is executed</span></div><div class="line"><span class="comment"> * ever 500ms. On each iteration, it fills one byte</span></div><div class="line"><span class="comment"> * to 1, 2 or 4 files and sends poll notification if</span></div><div class="line"><span class="comment"> * requested.</span></div><div class="line"><span class="comment"> */</span></div><div class="line"> <span class="keywordflow">for</span> (i = 0, t = idx; i < nr;</div><div class="line"> i++, t = (t + FSEL_FILES / nr) % FSEL_FILES) {</div><div class="line"> <span class="keywordflow">if</span> (fsel_cnt[t] == FSEL_CNT_MAX)</div><div class="line"> <span class="keywordflow">continue</span>;</div><div class="line"></div><div class="line"> fsel_cnt[t]++;</div><div class="line"> <span class="keywordflow">if</span> (fsel_fuse && (fsel_poll_notify_mask & (1 << t))) {</div><div class="line"> <span class="keyword">struct </span>fuse_pollhandle *ph;</div><div class="line"></div><div class="line"> printf(<span class="stringliteral">"NOTIFY %X\n"</span>, t);</div><div class="line"> ph = fsel_poll_handle[t];</div><div class="line"> fuse_notify_poll(ph);</div><div class="line"> <a class="code" href="fuse-3_810_81_2include_2fuse__common_8h.html#adf5027f8a38b2efc03858efd7fdc756a">fuse_pollhandle_destroy</a>(ph);</div><div class="line"> fsel_poll_notify_mask &= ~(1 << t);</div><div class="line"> fsel_poll_handle[t] = NULL;</div><div class="line"> }</div><div class="line"> }</div><div class="line"></div><div class="line"> idx = (idx + 1) % FSEL_FILES;</div><div class="line"> <span class="keywordflow">if</span> (idx == 0)</div><div class="line"> nr = (nr * 2) % 7; <span class="comment">/* cycle through 1, 2 and 4 */</span></div><div class="line"></div><div class="line"> pthread_mutex_unlock(&fsel_mutex);</div><div class="line"></div><div class="line"> nanosleep(&interval, NULL);</div><div class="line"> }</div><div class="line"></div><div class="line"> <span class="keywordflow">return</span> NULL;</div><div class="line">}</div><div class="line"></div><div class="line"><span class="keywordtype">int</span> main(<span class="keywordtype">int</span> argc, <span class="keywordtype">char</span> *argv[])</div><div class="line">{</div><div class="line"> pthread_t producer;</div><div class="line"> pthread_attr_t attr;</div><div class="line"> <span class="keywordtype">int</span> ret;</div><div class="line"></div><div class="line"> errno = pthread_mutex_init(&fsel_mutex, NULL);</div><div class="line"> <span class="keywordflow">if</span> (errno) {</div><div class="line"> perror(<span class="stringliteral">"pthread_mutex_init"</span>);</div><div class="line"> <span class="keywordflow">return</span> 1;</div><div class="line"> }</div><div class="line"></div><div class="line"> errno = pthread_attr_init(&attr);</div><div class="line"> <span class="keywordflow">if</span> (errno) {</div><div class="line"> perror(<span class="stringliteral">"pthread_attr_init"</span>);</div><div class="line"> <span class="keywordflow">return</span> 1;</div><div class="line"> }</div><div class="line"></div><div class="line"> errno = pthread_create(&producer, &attr, fsel_producer, NULL);</div><div class="line"> <span class="keywordflow">if</span> (errno) {</div><div class="line"> perror(<span class="stringliteral">"pthread_create"</span>);</div><div class="line"> <span class="keywordflow">return</span> 1;</div><div class="line"> }</div><div class="line"></div><div class="line"> ret = <a class="code" href="fuse-3_810_81_2include_2fuse_8h.html#ac99b844cee7aaa8fb4e35df5b5488d82">fuse_main</a>(argc, argv, &fsel_oper, NULL);</div><div class="line"></div><div class="line"> pthread_cancel(producer);</div><div class="line"> pthread_join(producer, NULL);</div><div class="line"></div><div class="line"> <span class="keywordflow">return</span> ret;</div><div class="line">}</div></div><!-- fragment -->
<p class="definition">Definition in file <a class="el" href="fuse-3_810_81_2example_2poll_8c_source.html">poll.c</a>.</p>
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