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<div class="title">Chapter 8: Threads with libssh </div> </div>
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<div class="textblock"><h1><a class="anchor" id="threads_with_libssh"></a>
How to use libssh with threads</h1>
<p>libssh may be used in multithreaded applications, but under several conditions :</p>
<ul>
<li>Threading must be initialized during the initialization of libssh. This initialization must be done outside of any threading context.</li>
<li>If pthreads is being used by your application (or your framework's backend), you must link with libssh_threads dynamic library and initialize threading with the ssh_threads_pthreads threading object.</li>
<li>If an other threading library is being used by your application, you must implement all the methods of the ssh_threads_callbacks_struct structure and initialize libssh with it.</li>
<li>At all times, you may use different sessions inside threads, make parallel connections, read/write on different sessions and so on. You <em>cannot</em> use a single session (or channels for a single session) in several threads at the same time. This will most likely lead to internal state corruption. This limitation is being worked out and will maybe disappear later.</li>
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<h2><a class="anchor" id="threads_init"></a>
Initialization of threads</h2>
<p>To initialize threading, you must first select the threading model you want to use, using <a class="el" href="group__libssh__threads.html#gaf473af3fbae6f1bb0e249fd1d079ff68" title="sets the thread callbacks necessary if your program is using libssh in a multithreaded fashion...">ssh_threads_set_callbacks()</a>, then call <a class="el" href="group__libssh.html#ga3ebf8d6920e563f3b032e3cd5277598e" title="Initialize global cryptographic data structures.">ssh_init()</a>.</p>
<div class="fragment"><div class="line"><span class="preprocessor">#include <libssh/callbacks.h></span></div>
<div class="line">...</div>
<div class="line">ssh_threads_set_callbacks(<a class="code" href="group__libssh__threads.html#ga10fa1f7243c94524b734a96963818c5b" title="returns a pointer on the noop threads callbacks, to be used with ssh_threads_set_callbacks.">ssh_threads_get_noop</a>());</div>
<div class="line"><a class="code" href="group__libssh.html#ga3ebf8d6920e563f3b032e3cd5277598e" title="Initialize global cryptographic data structures.">ssh_init</a>();</div>
</div><!-- fragment --><p>ssh_threads_noop is the threading structure that does nothing. It's the threading callbacks being used by default when you're not using threading.</p>
<h2><a class="anchor" id="threads_pthread"></a>
Using libpthread with libssh</h2>
<p>If your application is using libpthread, you may simply use the libpthread threading backend:</p>
<div class="fragment"><div class="line"><span class="preprocessor">#include <libssh/callbacks.h></span></div>
<div class="line">...</div>
<div class="line">ssh_threads_set_callbacks(ssh_threads_get_pthread());</div>
<div class="line"><a class="code" href="group__libssh.html#ga3ebf8d6920e563f3b032e3cd5277598e" title="Initialize global cryptographic data structures.">ssh_init</a>();</div>
</div><!-- fragment --><p>However, you must be sure to link with the library ssh_threads. If you're using gcc, you must use the commandline </p>
<div class="fragment"><div class="line">gcc -o output input.c -lssh -lssh_threads</div>
</div><!-- fragment --><h2><a class="anchor" id="threads_other"></a>
Using another threading library</h2>
<p>You must find your way in the ssh_threads_callbacks_struct structure. You must implement the following methods :</p>
<ul>
<li>mutex_lock</li>
<li>mutex_unlock</li>
<li>mutex_init</li>
<li>mutex_destroy</li>
<li>thread_id</li>
</ul>
<p>Good luck ! </p>
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