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= nng_http_handler_alloc(3)
//
// Copyright 2018 Staysail Systems, Inc. <info@staysail.tech>
// Copyright 2018 Capitar IT Group BV <info@capitar.com>
//
// This document is supplied under the terms of the MIT License, a
// copy of which should be located in the distribution where this
// file was obtained (LICENSE.txt). A copy of the license may also be
// found online at https://opensource.org/licenses/MIT.
//
== NAME
nng_http_handler_alloc - allocate HTTP server handler
== SYNOPSIS
[source, c]
-----------
#include <nng/nng.h>
#include <nng/supplemental/http/http.h>
typedef struct nng_http_handler nng_http_handler;
int nng_http_handler_alloc(nng_http_handler **hp, const char *path,
void (*func)(nng_aio *);
int nng_http_handler_alloc_directory(nng_http_handler **hp, const char *path,
const char *dirname);
int nng_http_handler_alloc_file(nng_http_handler **hp, const char *path,
const char *filename);
int nng_http_handler_alloc_static(nng_http_handler **hp, const char *path,
const void *data, size_t size, const char *content_type);
-----------
== DESCRIPTION
The `nng_http_handler_alloc()` family of functions allocate a handler
which will be used to process requests coming into an HTTP server.
On success, a pointer to the handler is stored at the located pointed to
by _hp_.
Every handler has a Request-URI to which it refers, which is determined
by the _path_ argument. Only the path component of the Request URI is
considered when determining whether the handler should be called.
Additionally each handler has a method it is registered to handle
(the default is "GET", see
<<nng_http_handler_set_method#,nng_http_handler_set_method(3)), and
optionally a 'Host' header it can be matched against (see
<<nng_http_handler_set_host#,nng_http_handler_set_host(3)).
In some cases, a handler may reference a logical tree rather (directory)
rather than just a single element.
(See <<nng_http_handler_set_tree#,nng_http_handler_set_tree(3)>>).
=== Custom Handler
The generic (first) form of this creates a handler that uses a user-supplied
function to process HTTP requests. This function uses the asynchronous I/O
framework. The function takes a pointer to an `nng_aio` structure. That
structure will be passed with the following input values (retrieved with
<<nng_aio_get_input#,nng_aio_get_input(3)>>):
0: ``nng_http_req *`` __request__:: The client's HTTP request.
1: ``nng_http_handler *``__handler__:: Pointer to the handler object.
2: ``nng_http_conn *``__conn__:: The underlying HTTP connection.
The handler should create an `nng_http_res *` response (such as via
<<nng_http_res_alloc#,nng_http_res_alloc(3)>> or
<<nng_http_res_alloc_error#,nng_http_res_alloc_error(3)>>) and store that
in as the first output (index 0) with
<<nng_aio_set_output#,nng_aio_set_output(3)>>.
Alternatively, the handler may send the HTTP response (and any associated
body data) itself using the connection. In that case the output at index
0 of the _aio_ should be NULL.
Finally, using the <<nng_aio_finish#,nng_aio_finish(3)>> function, the
_aio_ should be completed successfully. If any non-zero status is returned
back to the caller instead, then a generic 500 response will be created and
sent, if possible, and the connection will be closed.
=== Directory Handler
The second member of this family, `nng_http_handler_alloc_directory()`, creates
a handler configured to serve a directory tree. The _uri_ is taken as
the root, and files are served from the directory tree rooted at _path_.
When the client Request-URI resolves to a directory in the filesystem,
the handler looks first for a file named `index.html` or `index.htm`. If
one is found, then that file is returned back to the client. If no such
index file exists, then an `NNG_HTTP_STATUS_NOT_FOUND` (404) error is
sent back to the client.
The `Content-Type` will be set automatically based upon the extension
of the requsted file name. If a content type cannot be determined from
the extension, then `application/octet-stream` is used.
=== File Handler
The third member of this family, `nng_http_handler_alloc_file()`, creates
a handler to serve up a single file; it does not traverse directories
or search for `index.html` or `index.htm` files.
The `Content-Type` will be set automatically based upon the extension
of the requsted file name. If a content type cannot be determined from
the extension, then `application/octet-stream` is used.
=== Static Handler
The fourth member of this family, `nng_http_handler_alloc_static()`, creates
a handler to serve up fixed content located in program data. The client is
sent the _data_, with `Content-Length` of _size_ bytes, and `Content-Type` of
__content_type__.
== RETURN VALUES
This function returns 0 on success, and non-zero otherwise.
== ERRORS
`NNG_EINVAL`:: An invalid _path_ was specified.
`NNG_ENOMEM`:: Insufficient free memory exists to allocate a message.
`NNG_ENOTSUP`:: No support for HTTP in the library.
== SEE ALSO
<<nng_aio_finish#,nng_aio_finish(3)>>,
<<nng_aio_get_input#,nng_aio_get_input(3)>>,
<<nng_aio_set_output#,nng_aio_set_output(3)>>,
<<nng_http_handler_free#,nng_http_handler_free(3)>>,
<<nng_http_handler_set_host#,nng_http_handler_set_host(3)>>,
<<nng_http_handler_set_method#,nng_http_handler_set_method(3)>>,
<<nng_http_handler_set_tree#,nng_http_handler_set_tree(3)>>,
<<nng_http_res_alloc#,nng_http_res_alloc(3)>>,
<<nng_http_res_alloc_error#,nng_http_res_alloc_error(3)>>,
<<nng_http_server_add_handler#,nng_http_server_add_handler(3)>>,
<<nng_strerror#,nng_strerror(3)>>,
<<nng#,nng(7)>>
|
