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.
· OpenSSL requires global initialization to load shared lookup
· The SOCKS library requires initialization before use.
· 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
For some applications it may be necessary to call ne_i18n_init to
initialize the internationalization support in neon.
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.
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.
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.
As a pure library interface, neon will never produce output on stdout
or stderr; all user interaction is the responsibilty of the
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.
Joe Orton <email@example.com>