NEON(3)                       neon API reference                       NEON(3)

       neon - HTTP and WebDAV client library

       neon is an HTTP and WebDAV client library. The major abstractions
       exposed are the HTTP session, created by ne_session_create; and the
       HTTP request, created by ne_request_create. HTTP authentication is
       handled transparently for server and proxy servers, see
       ne_set_server_auth; complete SSL/TLS support is also included, see

       Some conventions are used throughout the neon API, to provide a
       consistent and simple interface; these are documented below.

   Thread-safeness and global initialization
       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 getaddrinfo interface, which neon supports; some others
       implement gethostbyname using thread-local storage.

       To allow thread-safe use of SSL in the OpenSSL and GnuTLS libraries
       neon must be configured using the --enable-threadsafe-ssl; if this is
       done, locking callbacks will be registered by ne_sock_init; note that
       care must be exercised if neon is used in conjunction with another
       library which uses OpenSSL or GnuTLS.

       Some platforms and libraries used by neon require global initialization
       before use; notably:

       ·   The SIGPIPE signal disposition must be set to ignored or otherwise
           handled to avoid process termination when writing to a socket which
           has been shutdown by the peer.

       ·   OpenSSL and GnuTLS require global initialization to load shared
           lookup tables.

       ·   The Win32 socket library requires initialization before use.

       The ne_sock_init 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
       ne_sock_init (and ne_sock_exit); neon neither checks whether these
       functions are called nor calls them itself.

       For some applications and configurations it may be necessary to call
       ne_i18n_init to initialize the support for internationalization in

   Asynchronous signal safety
       No function in neon is defined to be “async-signal safe” - 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.

   Functions using global state
       Any function in neon may modify the errno global variable as a
       side-effect. Except where explicitly documented, the value of errno is
       unspecified after any neon function call.

       Other than in the use of errno, the only functions which use or modify
       process-global state in neon are as follows:

       ·   ne_sock_init, ne_i18n_init, and ne_sock_exit, as described above

       ·   ne_debug_init and ne_debug, if enabled at compile time; for
           debugging output

       ·   ne_oom_callback for installing a process-global callback to be
           invoked on malloc failure

       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 namespace
       prefix. An application which ensures it uses no names with these
       prefixes is then guaranteed to avoid such collisions.

       The neon library reserves the use of the namespace prefixes ne_ and
       NE_. 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.

       SSL, ssl, TLS, tls, ERR_, BIO_, d2i_, i2d_, ASN1_
           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.

       gnutls_, gcry_, gpg_
           Namespaces used by the GnuTLS library (and dependencies thereof)

       XML_, Xml[A-Z]
           Namespaces used by the expat library.

       xml[A-Z], html[A-Z], docb[A-Z]
           Namespaces used by the libxml2 library; a relatively small number
           of symbols are used without these prefixes.

       inflate, deflate, crc32, compress, uncompres, adler32, zlib
           Namespaces used by the zlib library; a relatively small number of
           symbols are used without these prefixes.

       krb5, gss, GSS, asn1, decode_krb5, encode_krb5, profile, mit
           Some of the prefixes used by the MIT GSSAPI library and
           dependencies thereof; a number of symbols lie outside these

           Namespace used by the pakchois library.

           Namespace used by the libproxy library.

   Argument validation
       neon does not attempt to validate that the parameters passed to
       functions conform to the API (for instance, checking that pointer
       arguments are not NULL). Any use of the neon API which is not
       documented to produce a certain behaviour results is said to produce
       undefined behaviour; it is likely that neon will segfault under these

   URI paths, WebDAV metadata
       The path strings passed to any function must be URI-encoded 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.

   User interaction
       As a pure library interface, neon will never produce output on stdout
       or stderr; all user interaction is the responsibilty of the

   Memory handling
       neon does not attempt to cope gracefully with an out-of-memory
       situation; instead, by default, the abort function is called to
       immediately terminate the process. An application may register a custom
       function which will be called before abort in such a situation; see

   Callbacks and userdata
       Whenever a callback is registered, a userdata pointer is also used to
       allow the application to associate a context with the callback. The
       userdata is of type void *, allowing any pointer to be used.

   Large File Support
       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 off_t type, where LFS support is

       Some interfaces use the ne_off_t type, which is defined to be either
       off_t or off64_t according to whether LFS support is detected at build
       time. neon does not use or require the -D_FILE_OFFSET_BITS=64 macro

       ne_session_create(3), ne_oom_callback

       Joe Orton <>

neon 0.29.3                     11 January 2010                        NEON(3)