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<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>neon</title><link rel="stylesheet" type="text/css" href="../manual.css"><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"><link rel="home" href="index.html" title="neon HTTP/WebDAV client library"><link rel="up" href="ref.html" title="neon API reference"><link rel="prev" href="ref.html" title="neon API reference"><link rel="next" href="refconfig.html" title="neon-config"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">neon</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ref.html">Prev</a> </td><th width="60%" align="center">neon API reference</th><td width="20%" align="right"> <a accesskey="n" href="refconfig.html">Next</a></td></tr></table><hr></div><div class="refentry"><a name="refneon"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>neon — HTTP and WebDAV client library</p></div><div class="refsect1"><a name="idm140368851469392"></a><h2>Description</h2><p>neon is an HTTP and WebDAV client library.  The major
    abstractions exposed are the HTTP <span class="emphasis"><em>session</em></span>,
    created by <a class="xref" href="refsess.html#ne_session_create">ne_session_create</a>; and the HTTP
    <span class="emphasis"><em>request</em></span>, created by <a class="xref" href="refreq.html#ne_request_create">ne_request_create</a>.  HTTP authentication is handled
    transparently for server and proxy servers, see <a class="xref" href="refauth.html#ne_set_server_auth">ne_set_server_auth</a>; complete SSL/TLS support is also
    included, see <a class="xref" href="refsslvfy.html#ne_ssl_set_verify">ne_ssl_set_verify</a>.</p></div><div class="refsect1"><a name="idm140368851464416"></a><h2>Conventions</h2><p>Some conventions are used throughout the neon API, to
    provide a consistent and simple interface; these are documented
    below.</p><div class="refsect2"><a name="idm140368851463248"></a><h3>Thread-safeness and global initialization</h3><p>neon itself is implemented to be thread-safe (avoiding any
    use of global state), but relies on the operating system providing
    a thread-safe resolver interface.  Modern operating systems offer
    the thread-safe <code class="function">getaddrinfo</code> interface, which
    neon supports; some others implement
    <code class="function">gethostbyname</code> using thread-local
    storage.</p><p>To allow thread-safe use of SSL in the OpenSSL and GnuTLS
    libraries neon must be configured using the
    <code class="literal">--enable-threadsafe-ssl</code>; if this is done,
    locking callbacks will be registered by <a class="xref" href="refsockinit.html#ne_sock_init">ne_sock_init</a>; note that care must be exercised if
    neon is used in conjunction with another library which uses
    OpenSSL or GnuTLS.</p><p>Some platforms and libraries used by neon require global
    initialization before use; notably:

    </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">The <code class="literal">SIGPIPE</code> signal
      disposition must be set to <span class="emphasis"><em>ignored</em></span> or
      otherwise handled to avoid process termination when writing to a
      socket which has been shutdown by the peer.</li><li class="listitem">OpenSSL and GnuTLS require global
      initialization to load shared lookup
      tables.</li><li class="listitem">The Win32 socket library requires
      initialization before use.</li></ul></div><p>

    The <a class="xref" href="refsockinit.html#ne_sock_init">ne_sock_init</a> function should be called
    before any other use of neon to perform any necessary
    initialization needed for the particular platform.  Applications
    wishing to perform all the necessary process-global initialization
    steps themselves may omit to call <a class="xref" href="refsockinit.html#ne_sock_init">ne_sock_init</a>
    (and <a class="xref" href="refsockinit.html#ne_sock_exit">ne_sock_exit</a>); neon neither checks whether
    these functions are called nor calls them itself.</p><p>For some applications and configurations it may be necessary
    to call <a class="xref" href="refi18n.html#ne_i18n_init">ne_i18n_init</a> to initialize the support
    for internationalization in neon.</p></div><div class="refsect2"><a name="idm140368851410560"></a><h3>Asynchronous signal safety</h3><p>No function in neon is defined to be <span class="quote">“<span class="quote">async-signal safe</span>”</span> -
    that is, no function is safe to call from a signal handler.  Any
    call into the neon library from a signal handler will have
    undefined behaviour - in other words, it may crash the
    process.</p></div><div class="refsect2"><a name="idm140368851408688"></a><h3>Functions using global state</h3><p>Any function in neon may modify the
    <code class="literal">errno</code> global variable as a side-effect.  Except
    where explicitly documented, the value of <code class="literal">errno</code>
    is unspecified after any neon function call.</p><p>Other than in the use of <code class="literal">errno</code>, the only
    functions which use or modify process-global state in neon are
    as follows:

    </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><a class="xref" href="refsockinit.html#ne_sock_init">ne_sock_init</a>, <a class="xref" href="refi18n.html#ne_i18n_init">ne_i18n_init</a>, and <a class="xref" href="refsockinit.html#ne_sock_exit">ne_sock_exit</a>, as
      described above</li><li class="listitem"><code class="function">ne_debug_init</code> and
      <code class="function">ne_debug</code>, if enabled at compile time; for
      debugging output</li><li class="listitem"><a class="xref" href="refalloc.html#ne_oom_callback">ne_oom_callback</a> for
      installing a process-global callback to be invoked on
      <code class="function">malloc</code> failure</li></ul></div></div><div class="refsect2"><a name="idm140368851399744"></a><h3>Namespaces</h3><p>To avoid possible collisions between names used for symbols
    and preprocessor macros by an application and the libraries it
    uses, it is good practice for each library to reserve a particular
    <span class="emphasis"><em>namespace prefix</em></span>.  An application which
    ensures it uses no names with these prefixes is then guaranteed to
    avoid such collisions.</p><p>The neon library reserves the use of the namespace
    prefixes <code class="literal">ne_</code> and <code class="literal">NE_</code>.  The
    libraries used by neon may also reserve certain namespaces;
    collisions between these libraries and a neon-based application
    will not be detected at compile time, since the underlying library
    interfaces are not exposed through the neon header files.  Such
    collisions can only be detected at link time, when the linker
    attempts to resolve symbols.  The following list documents some of
    the namespaces claimed by libraries used by neon; this list may
    be incomplete.</p><div class="variablelist"><table border="0" class="variablelist"><colgroup><col align="left" valign="top"><col></colgroup><tbody><tr><td><p><span class="term">SSL, ssl, TLS, tls, ERR_, BIO_, d2i_, i2d_, ASN1_</span></p></td><td>Some of the many prefixes used by the OpenSSL
	library; little attempt has been made to keep exported symbols
	within any particular prefixes for this
	library.</td></tr><tr><td><p><span class="term">gnutls_, gcry_, gpg_</span></p></td><td>Namespaces used by the GnuTLS library (and
        dependencies thereof)</td></tr><tr><td><p><span class="term">XML_, Xml[A-Z]</span></p></td><td>Namespaces
	used by the expat library.</td></tr><tr><td><p><span class="term">xml[A-Z], html[A-Z], docb[A-Z]</span></p></td><td>Namespaces used by the libxml2 library; a
	relatively small number of symbols are used without these
	prefixes.</td></tr><tr><td><p><span class="term">inflate, deflate, crc32, compress, uncompres, adler32,
        zlib</span></p></td><td>Namespaces used by the zlib library; a
	relatively small number of symbols are used without these
	prefixes.</td></tr><tr><td><p><span class="term">krb5, gss, GSS, asn1, decode_krb5, encode_krb5, profile,
        mit</span></p></td><td>Some of the prefixes used by the MIT GSSAPI
        library and dependencies thereof; a number of symbols lie
        outside these prefixes.</td></tr><tr><td><p><span class="term">pakchois_</span></p></td><td>Namespace used by the pakchois 
         library.</td></tr><tr><td><p><span class="term">px_</span></p></td><td>Namespace used by the libproxy
         library.</td></tr></tbody></table></div></div><div class="refsect2"><a name="idm140368851384144"></a><h3>Argument validation</h3><p>neon does not attempt to validate that the parameters
    passed to functions conform to the API (for instance, checking
    that pointer arguments are not <code class="literal">NULL</code>).  Any use of the neon API
    which is not documented to produce a certain behaviour results is
    said to produce <span class="emphasis"><em>undefined behaviour</em></span>; it is
    likely that neon will segfault under these conditions.</p></div><div class="refsect2"><a name="idm140368851380992"></a><h3>URI paths, WebDAV metadata</h3><p>The path strings passed to any function must be
    <span class="emphasis"><em>URI-encoded</em></span> by the application; neon never
    performs any URI encoding or decoding internally.  WebDAV property
    names and values must be valid UTF-8 encoded Unicode
    strings.</p></div><div class="refsect2"><a name="idm140368851379200"></a><h3>User interaction</h3><p>As a pure library interface, neon will never produce
    output on <code class="constant">stdout</code> or
    <code class="constant">stderr</code>; all user interaction is the
    responsibilty of the application.</p></div><div class="refsect2"><a name="idm140368851376816"></a><h3>Memory handling</h3><p>neon does not attempt to cope gracefully with an
    out-of-memory situation; instead, by default, the
    <code class="function">abort</code> function is called to immediately
    terminate the process.  An application may register a custom
    function which will be called before <code class="function">abort</code> in
    such a situation; see <a class="xref" href="refalloc.html#ne_oom_callback">ne_oom_callback</a>.</p></div><div class="refsect2"><a name="idm140368851373296"></a><h3>Callbacks and userdata</h3><p>Whenever a callback is registered, a
    <code class="literal">userdata</code> pointer is also used to allow the
    application to associate a context with the callback.  The
    userdata is of type <em class="type">void *</em>, allowing any pointer to
    be used.</p></div><div class="refsect2"><a name="idm140368851370848"></a><h3>Large File Support</h3><p>Since version 0.27.0, neon transparently uses the "LFS
    transitional" interfaces in places where file-backed file
    descriptors are manipulated.  This means files larger than 2GiB
    can be handled on platforms with a native 32-bit
    <code class="literal">off_t</code> type, where LFS support is
    available.</p><p>Some interfaces use the <code class="literal">ne_off_t</code> type,
    which is defined to be either <code class="literal">off_t</code> or
    <code class="literal">off64_t</code> according to whether LFS support is
    detected at build time.  neon does not use or require the
    <code class="literal">-D_FILE_OFFSET_BITS=64</code> macro definition.</p></div></div><div class="refsect1"><a name="idm140368851365408"></a><h2>See also</h2><p><a class="xref" href="refsess.html" title="ne_session_create"><span class="refentrytitle">ne_session_create</span></a>, <a class="xref" href="refalloc.html#ne_oom_callback">ne_oom_callback</a></p></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ref.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="ref.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="refconfig.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">neon API reference </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> neon-config</td></tr></table></div></body></html>