# Module Ocsigen_extensions

    module Ocsigen_extensions: sig .. end

Writing extensions for Ocsigen

    exception Ocsigen_http_error of (Ocsigen_http_frame.cookieset * int)

    exception Ocsigen_Is_a_directory

    exception Ocsigen_malformed_url

    exception Ocsigen_Internal_Error of string

    exception Bad_config_tag_for_extension of string

Try next extension

    exception Error_in_config_file of string

Stop with an error message

    val badconfig : ('a, unit, string, 'b) Pervasives.format4 -> 'a

Convenient function for raising Error_in_config_file exceptions with a sprintf-formatted argument.

    type url_path = string list

The type of URL paths. `["plop";"plip"]` corresponds to `plop/plip`.

    val string_of_url_path : url_path -> string

`type ``virtual_host_part =`

`|` | `Text of `string * int``
`|` | `Wildcard`

    type virtual_hosts = (virtual_host_part list * int option) list

`type ``file_info = {`

`` | `tmp_filename : `string`;` | `(*` | Where the file is stored on the server | `*)`
`` | `filesize : `int64`;` | `(*` | Size, in bytes | `*)`
`` | `raw_original_filename : `string`;` | `(*` | Original file name, as given by the client. | `*)`
`` | `original_basename : `string`;` | `(*` | Original file name | `*)`

}
The files sent in the request

Note that the files are cancelled once the request has been fulfilled

Only IE is known to make `raw_original_filename` and `original_basename` differ, as it sends the full original path of uploaded files. In all cases, `original_basename` is the basename of the file. More precisely, it is the part of the filename after the last `/` or `\` , if any, or `"none"` if one of these characters is the last one. You should probably never use `raw_original_filename`.

    type client

A value of this type represents the client who did the request.

    val client_id : client -> int

Returns the id number of the connection

    val client_connection : client -> Ocsigen_http_com.connection

Returns the connection
`type ``request_info = {`

`` | `ri_url_string : `string`;` | `(*` | full URL | `*)`
`` | `ri_url : `Neturl.url`;`
`` | `ri_method : `Ocsigen_http_frame.Http_header.http_method`;` | `(*` | GET, POST, HEAD... | `*)`
`` | `ri_protocol : `Ocsigen_http_frame.Http_header.proto`;` | `(*` | HTTP protocol used by client (1.0 or 1.1) | `*)`
`` | `ri_ssl : `bool`;` | `(*` | true if HTTPS, false if HTTP | `*)`
`` | `ri_full_path_string : `string`;` | `(*` | full path of the URL | `*)`
`` | `ri_full_path : `string list`;` | `(*` | full path of the URL | `*)`
`` | `ri_sub_path : `string list`;` | `(*` | path of the URL (only part concerning the site) | `*)`
`` | `ri_sub_path_string : `string`;` | `(*` | path of the URL (only part concerning the site) | `*)`
`` | `ri_get_params_string : `string option`;` | `(*` | string containing GET parameters | `*)`
`` | `ri_host : `string option`;` | `(*` | Host field of the request (if any) | `*)`
`` | `ri_get_params : `(string * string) list Lazy.t`;` | `(*` | Association list of get parameters | `*)`
`` | `ri_initial_get_params : `(string * string) list Lazy.t`;` | `(*` | Association list of get parameters, as sent by the browser (must not be modified by extensions) | `*)`
`` | `ri_post_params : `(string * string) list Lwt.t Lazy.t`;` | `(*` | Association list of post parameters | `*)`
`` | `ri_files : `(string * file_info) list Lwt.t Lazy.t`;` | `(*` | Files sent in the request | `*)`
`` | `ri_remote_inet_addr : `Unix.inet_addr`;` | `(*` | IP of the client | `*)`
`` | `ri_remote_ip : `string`;` | `(*` | IP of the client | `*)`
`` | `ri_remote_ip_parsed : `Ocsigen_lib.ip_address Lazy.t`;` | `(*` | IP of the client, parsed | `*)`
`` | `ri_remote_port : `int`;` | `(*` | Port used by the client | `*)`
`` | `ri_server_port : `int`;` | `(*` | Port of the request (server) | `*)`
`` | `ri_user_agent : `string`;` | `(*` | User_agent of the browser | `*)`
`` | `ri_cookies_string : `string option Lazy.t`;` | `(*` | Cookies sent by the browser | `*)`
`` | `ri_cookies : `string Ocsigen_http_frame.Cookievalues.t Lazy.t`;` | `(*` | Cookies sent by the browser | `*)`
`` | `ri_ifmodifiedsince : `float option`;` | `(*` | if-modified-since field | `*)`
`` | `ri_ifunmodifiedsince : `float option`;` | `(*` | if-unmodified-since field | `*)`
`` | `ri_ifnonematch : `string list`;` | `(*` | if-none-match field ( * and weak entity tags not implemented) | `*)`
`` | `ri_ifmatch : `string list option`;` | `(*` | if-match field ( * not implemented) | `*)`
`` | `ri_content_type : `((string * string) * (string * string) list) option`;` | `(*` | Content-Type HTTP header | `*)`
`` | `ri_content_type_string : `string option`;` | `(*` | Content-Type HTTP header | `*)`
`` | `ri_content_length : `int64 option`;` | `(*` | Content-Length HTTP header | `*)`
`` | `ri_referer : `string option Lazy.t`;` | `(*` | Referer HTTP header | `*)`
`` | `ri_accept : `((string option * string option) * float option * (string * string) list) list Lazy.t`;` | `(*` | Accept HTTP header. For example `(Some "text", None)` means `"text/*"`. The float is the "quality" value, if any. The last association list is for other extensions. | `*)`
`` | `ri_accept_charset : `(string option * float option) list Lazy.t`;` | `(*` | Accept-Charset HTTP header. `None` for the first value means "*". The float is the "quality" value, if any. | `*)`
`` | `ri_accept_encoding : `(string option * float option) list Lazy.t`;` | `(*` | Accept-Encoding HTTP header. `None` for the first value means "*". The float is the "quality" value, if any. | `*)`
`` | `ri_accept_language : `(string * float option) list Lazy.t`;` | `(*` | Accept-Language HTTP header. The float is the "quality" value, if any. | `*)`
`` | `ri_http_frame : `Ocsigen_http_frame.t`;` | `(*` | The full http_frame | `*)`
`` | `ri_extension_info : `exn list`;` | `(*` | Use this to put anything you want, for example, information for subsequent extensions | `*)`
`` | `ri_client : `client`;` | `(*` | The request connection | `*)`

}
The request
If you force `ri_files` or `ri_post_params`, the request is fully read, so it is not possible any more to read it from `ri_http_frame` (and vice versa).
`type ``answer =`

`|` | `Ext_found of `(unit -> Ocsigen_http_frame.result Lwt.t)`` | `(*` | "OK stop! I will take the page. You can start the following request of the same pipelined connection. Here is the function to generate the page". The extension must return Ext_found as soon as possible when it is sure it is safe to start next request. Usually as soon as you know tha the result will be Ext_found. But in some case, for example proxies, you don't want the request of one connection to be handled in different order. In that case, wait to be sure that the new request will not overtake this one. | `*)`
`|` | `Ext_next of `int`` | `(*` | Page not found. Try next extension. The integer is the HTTP error code. It is usally 404, but may be for ex 403 (forbidden) if you want another extension to try after a 403. Same as Ext_continue_with but does not change the request. | `*)`
`|` | `Ext_stop_site of `(Ocsigen_http_frame.cookieset * int)`` | `(*` | Error. Do not try next extension, but try next site. The integer is the HTTP error code, usally 403. | `*)`
`|` | `Ext_stop_host of `(Ocsigen_http_frame.cookieset * int)`` | `(*` | Error. Do not try next extension, do not try next site, but try next host. The integer is the HTTP error code, usally 403. | `*)`
`|` | `Ext_stop_all of `(Ocsigen_http_frame.cookieset * int)`` | `(*` | Error. Do not try next extension (even filters), do not try next site, do not try next host, do not . The integer is the HTTP error code, usally 403. | `*)`
`|` | `Ext_continue_with of `(request_info * Ocsigen_http_frame.cookieset * int)`` | `(*` | Used to modify the request before giving it to next extension. The extension returns the request_info (possibly modified) and a set of cookies if it wants to set or cookies (`!Ocsigen_http_frame.Cookies.empty` for no cookies). You must add these cookies yourself in request_info if you want them to be seen by subsequent extensions, for example using `Ocsigen_http_frame.compute_new_ri_cookies`. The integer is usually equal to the error code received from preceding extension (but you may want to modify it). | `*)`
`|` | `Ext_retry_with of `request_info * Ocsigen_http_frame.cookieset`` | `(*` | Used to retry all the extensions with a new request_info. The extension returns the request_info (possibly modified) and a set of cookies if it wants to set or cookies (`!Ocsigen_http_frame.Cookies.empty` for no cookies). You must add these cookies yourself in request_info if you want them to be seen by subsequent extensions, for example using `Ocsigen_http_frame.compute_new_ri_cookies`. | `*)`
`|` | `Ext_sub_result of `extension2`` | `(*` | Used if your extension want to define option that may contain other options from other extensions. In that case, while parsing the configuration file, call the parsing function (of type `parse_fun`), that will return something of type `extension2`. | `*)`

`type ``request_state =`

`|` | `Req_not_found of `(int * request_info)``
`|` | `Req_found of `(request_info * (unit -> Ocsigen_http_frame.result Lwt.t))``

    type extension2 = (unit -> unit) ->
           Ocsigen_http_frame.cookieset ->
           request_state ->
           (answer * Ocsigen_http_frame.cookieset) Lwt.t

    type extension = request_state -> answer Lwt.t

For each <site> tag in the configuration file, you can set the extensions you want. Each extension is implemented as a function, taking the charset found in configuration file, the current state of the request, and returning an answer. If no page has been generated so far (`Req_not_found`), it receive the error code given by the previous extension (default 404), and the request information. If a page has been generated by previous extensions (case `Req_found`), the extension may want to modify the result (filters).

    type parse_fun = Simplexmlparser.xml list -> extension2

    type parse_host

    val register_extension : ?respect_pipeline:bool ->
           (virtual_hosts ->
            url_path ->
            string * string * int * int ->
            parse_host ->
            parse_fun ->
            Simplexmlparser.xml -> extension) ->
           (virtual_hosts ->
            url_path ->
            string * string * int * int ->
            parse_host ->
            parse_fun ->
            Simplexmlparser.xml -> extension) ->
           (unit -> unit) -> (unit -> unit) -> (exn -> string) -> unit

For each extension generating pages, we register four functions:

- a function taking
  - the name of the virtual <host>
  that will be called for each <host>, and that will generate a function taking:
  - the path attribute of a <site> tag
  that will be called for each <site>, and that will generate a function taking:
  - an item of the config file
  that will be called on each tag inside <site> and:
  - raise `Bad_config_tag_for_extension` if it does not recognize that tag
  - return something of type `extension` (filter or page generator)
- a function of same type, that will be called every time user configuration files are parsed (if userconf is enabled). It must define only safe options, for example it is not safe to allow such options to load a cmo specified by a user, or to execute a program, as this program will be executed by ocsigen's user. Note that function will be called for every request, whereas the first one is called only when starting or reloading the server. If you do not want to allow users to use your extension, use the predefined function `void_extension` (defines no option).
- a function that will be called at the beginning of the initialisation phase (each time the config file is reloaded) (Note that the extensions are not reloaded)
- a function that will be called at the end of the initialisation phase of the server
- a function that will create an error message from the exceptions that may be raised during the initialisation phase, and raise again all other exceptions

If the optional parameter `?respect_pipeline` is `true`, the extension will ask the server to respect the order of the pipeline. That means that it will wait to be sure that the previous request from the same connection has been taken by an extension before giving a request to an extension. Use this to write proxies extensions, when you want to be able to pipeline the requests you to another server. It is false by default.

    val void_extension : virtual_hosts ->
           url_path ->
           string * string * int * int ->
           parse_host ->
           parse_fun ->
           Simplexmlparser.xml -> extension

A predefined function to be passed to `Ocsigen_extensions.register_extension` that defines no option.

    val get_config : unit -> Simplexmlparser.xml list

While loading an extension, get the configuration tree between <dynlink></dynlink>

    val ri_of_url : string -> request_info -> request_info

Parsing URLs. This allows to modify the URL in the request_info. (to be used for example with Ext_retry_with or Ext_continue_with)
User directories

    type ud_string

The type for string that may contain a $u(...)

    val parse_user_dir : string -> ud_string

    val replace_user_dir : Netstring_pcre.regexp -> ud_string -> string -> string

raises `Not_found` is the directory does not exist