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-- --
-- --
-- G N A T . C G I --
-- --
-- S p e c --
-- --
-- Copyright (C) 2000-2003 Ada Core Technologies, Inc. --
-- --
-- GNAT is free software; you can redistribute it and/or modify it under --
-- terms of the GNU General Public License as published by the Free Soft- --
-- ware Foundation; either version 2, or (at your option) any later ver- --
-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
-- for more details. You should have received a copy of the GNU General --
-- Public License distributed with GNAT; see file COPYING. If not, write --
-- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
-- MA 02111-1307, USA. --
-- --
-- As a special exception, if other files instantiate generics from this --
-- unit, or you link this unit with other files to produce an executable, --
-- this unit does not by itself cause the resulting executable to be --
-- covered by the GNU General Public License. This exception does not --
-- however invalidate any other reasons why the executable file might be --
-- covered by the GNU Public License. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- --
-- This is a package to interface a GNAT program with a Web server via the
-- Common Gateway Interface (CGI).
-- Other related packages are:
-- GNAT.CGI.Cookie which deal with Web HTTP Cookies.
-- GNAT.CGI.Debug which output complete CGI runtime environment
-- Basically this package parse the CGI parameter which are a set of key/value
-- pairs. It builds a table whose index is the key and provides some services
-- to deal with this table.
-- Example:
-- Consider the following simple HTML form to capture a client name:
-- <html>
-- <head>
-- <title>My Web Page</title>
-- </head>
-- <body>
-- <form action="/cgi-bin/new_client" method="POST">
-- <input type=text name=client_name>
-- <input type=submit name="Enter">
-- </form>
-- </body>
-- </html>
-- The following program will retrieve the client's name:
-- with GNAT.CGI;
-- procedure New_Client is
-- use GNAT;
-- procedure Add_Client_To_Database (Name : in String) is
-- begin
-- ...
-- end Add_Client_To_Database;
-- begin
-- -- Check that we have 2 arguments (there is two inputs tag in
-- -- the HTML form) and that one of them is called "client_name".
-- if CGI.Argument_Count = 2
-- and the CGI.Key_Exists ("client_name")
-- then
-- Add_Client_To_Database (CGI.Value ("client_name"));
-- end if;
-- ...
-- CGI.Put_Header;
-- Text_IO.Put_Line ("<html><body>< ... Ok ... >");
-- exception
-- when CGI.Data_Error =>
-- CGI.Put_Header ("Location: /htdocs/error.html");
-- -- This returns the address of a Web page to be displayed
-- -- using a "Location:" header style.
-- end New_Client;
-- Note that the names in this package interface have been designed so that
-- they read nicely with the CGI prefix. The recommended style is to avoid
-- a use clause for GNAT.CGI, but to include a use clause for GNAT.
-- This package builds up a table of CGI parameters whose memory is not
-- released. A CGI program is expected to be a short lived program and
-- so it is adequate to have the underlying OS free the program on exit.
package GNAT.CGI is
Data_Error : exception;
-- This is raised when there is a problem with the CGI protocol. Either
-- the data could not be retrieved or the CGI environment is invalid.
-- The package will initialize itself by parsing the runtime CGI
-- environment during elaboration but we do not want to raise an
-- exception at this time, so the exception Data_Error is deferred
-- and will be raised when calling any services below (except for Ok).
Parameter_Not_Found : exception;
-- This exception is raised when a specific parameter is not found.
Default_Header : constant String := "Content-type: text/html";
-- This is the default header returned by Put_Header. If the CGI program
-- returned data is not an HTML page, this header must be change to a
-- valid MIME type.
type Method_Type is (Get, Post);
-- The method used to pass parameter from the Web client to the
-- server. With the GET method parameters are passed via the command
-- line, with the POST method parameters are passed via environment
-- variables. Others methods are not supported by this implementation.
type Metavariable_Name is
Document_Root, -- Web server dependent
Remote_Port, -- Web server dependent
Request_URI, -- Web server dependent
Script_Filename, -- Web server dependent
Server_Addr, -- Web server dependent
Server_Admin, -- Web server dependent
Server_Signature, -- Web server dependent
-- CGI metavariables that are set by the Web server during program
-- execution. All these variables are part of the restricted CGI runtime
-- environment and can be read using Metavariable service. The detailed
-- meanings of these metavariables are out of the scope of this
-- description. Please refer to for a description
-- of the CGI specification. Some metavariables are Web server dependent
-- and are not described in the cited document.
procedure Put_Header
(Header : String := Default_Header;
Force : Boolean := False);
-- Output standard CGI header by default. The header string is followed by
-- an empty line. This header must be the first answer sent back to the
-- server. Do nothing if this function has already been called and Force
-- is False.
function Ok return Boolean;
-- Returns True if the CGI environment is valid and False otherwise.
-- Every service used when the CGI environment is not valid will raise
-- the exception Data_Error.
function Method return Method_Type;
-- Returns the method used to call the CGI.
function Metavariable
(Name : Metavariable_Name;
Required : Boolean := False)
return String;
-- Returns parameter Name value. Returns the null string if Name
-- environment variable is not defined or raises Data_Error if
-- Required is set to True.
function Metavariable_Exists (Name : Metavariable_Name) return Boolean;
-- Returns True if the environment variable Name is defined in
-- the CGI runtime environment and False otherwise.
function URL return String;
-- Returns the URL used to call this script without the parameters.
-- The URL form is: http://<server_name>[:<server_port>]<script_name>
function Argument_Count return Natural;
-- Returns the number of parameters passed to the client. This is the
-- number of input tags in a form or the number of parameters passed to
-- the CGI via the command line.
-- Services to retrieve key/value CGI parameters --
function Value
(Key : String;
Required : Boolean := False)
return String;
-- Returns the parameter value associated to the parameter named Key.
-- If parameter does not exist, returns an empty string if Required
-- is False and raises the exception Parameter_Not_Found otherwise.
function Value (Position : Positive) return String;
-- Returns the parameter value associated with the CGI parameter number
-- Position. Raises Parameter_Not_Found if there is no such parameter
-- (i.e. Position > Argument_Count)
function Key_Exists (Key : String) return Boolean;
-- Returns True if the parameter named Key existx and False otherwise.
function Key (Position : Positive) return String;
-- Returns the parameter key associated with the CGI parameter number
-- Position. Raises the exception Parameter_Not_Found if there is no
-- such parameter (i.e. Position > Argument_Count)
with procedure
(Key : String;
Value : String;
Position : Positive;
Quit : in out Boolean);
procedure For_Every_Parameter;
-- Iterate through all existing key/value pairs and call the Action
-- supplied procedure. The Key and Value are set appropriately, Position
-- is the parameter order in the list, Quit is set to True by default.
-- Quit can be set to False to control the iterator termination.
function Decode (S : String) return String;
-- Decode Web string S. A string when passed to a CGI is encoded,
-- this function will decode the string to return the original
-- string's content. Every triplet of the form %HH (where H is an
-- hexadecimal number) is translated into the character such that:
-- Hex (Character'Pos (C)) = HH.