Add documentation in RDoc format.

git-svn-id: http://svn.ruby-lang.org/repos/ruby/trunk@4455 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 278 insertions, 4 deletions

diff --git a/lib/cgi/session.rb b/lib/cgi/session.rb
index 0ce82b392..4ad6bf2a6 100644
--- a/lib/cgi/session.rb
+++ b/lib/cgi/session.rb
@@ -1,21 +1,175 @@
+#
+# cgi/session.rb - session support for cgi scripts
+#
 # Copyright (C) 2001  Yukihiro "Matz" Matsumoto
 # Copyright (C) 2000  Network Applied Communication Laboratory, Inc.
 # Copyright (C) 2000  Information-technology Promotion Agency, Japan
+#
+# Author: Yukihiro "Matz" Matsumoto
+#
+# Documentation: William Webber (william@williamwebber.com)
+#
+# == Overview
+#
+# This file provides the +CGI::Session+ class, which provides session
+# support for CGI scripts.  A session is a sequence of HTTP requests
+# and responses linked together and associated with a single client.  
+# Information associated with the session is stored
+# on the server between requests.  A session id is passed between client
+# and server with every request and response, transparently
+# to the user.  This adds state information to the otherwise stateless
+# HTTP request/response protocol.
+#
+# See the documentation to the +CGI::Session+ class for more details
+# and examples of usage.  See cgi.rb for the +CGI+ class itself.
 
 require 'cgi'
 require 'tmpdir'
 
 class CGI
+
+  # Class representing an HTTP session.  See documentation for the file 
+  # cgi/session.rb for an introduction to HTTP sessions.
+  #
+  # == Lifecycle
+  #
+  # A CGI::Session instance is created from a CGI object.  By default,
+  # this CGI::Session instance will start a new session if none currently
+  # exists, or continue the current session for this client if one does
+  # exist.  The +new_session+ option can be used to either always or
+  # never create a new session.  See #new() for more details.
+  #
+  # #delete() deletes a session from session storage.  It
+  # does not however remove the session id from the client.  If the client
+  # makes another request with the same id, the effect will be to start
+  # a new session with the old session's id.
+  #
+  # == Setting and retrieving session data.
+  #
+  # The Session class associates data with a session as key-value pairs.
+  # This data can be set and retrieved by indexing the Session instance 
+  # using '[]', much the same as hashes (although other hash methods
+  # are not supported).
+  #
+  # When session processing has been completed for a request, the
+  # session should be closed using the close() method.  This will
+  # store the session's state to persistent storage.  If you want
+  # to store the session's state to persistent storage without
+  # finishing session processing for this request, call the update()
+  # method.
+  #
+  # == Storing session state
+  #
+  # The caller can specify what form of storage to use for the session's 
+  # data with the +database_manager+ option to CGI::Session::new.  The
+  # following storage classes are provided as part of the standard library:
+  #
+  # CGI::Session::FileStore:: stores data as plain text in a flat file.  Only 
+  #                           works with String data.  This is the default 
+  #                           storage type.
+  # CGI::Session::MemoryStore:: stores data in an in-memory hash.  The data 
+  #                             only persists for as long as the current ruby 
+  #                             interpreter instance does.
+  # CGI::Session::PStore:: stores data in Marshalled format.  Provided by
+  #                        cgi/session/pstore.rb.  Supports data of any type, 
+  #                        and provides file-locking and transaction support.
+  #
+  # Custom storage types can also be created by defining a class with 
+  # the following methods:
+  #
+  #    new(session, options)
+  #    restore  # returns hash of session data.
+  #    update
+  #    close
+  #    delete
+  #
+  # Changing storage type mid-session does not work.  Note in particular
+  # that by default the FileStore and PStore session data files have the
+  # same name.  If your application switches from one to the other without
+  # making sure that filenames will be different
+  # and clients still have old sessions lying around in cookies, then
+  # things will break nastily!
+  #
+  # == Maintaining the session id.
+  #
+  # Most session state is maintained on the server.  However, a session
+  # id must be passed backwards and forwards between client and server
+  # to maintain a reference to this session state.
+  #
+  # The simplest way to do this is via cookies.  The CGI::Session class
+  # provides transparent support for session id communication via cookies
+  # if the client has cookies enabled.
+  # 
+  # If the client has cookies disabled, the session id must be included
+  # as a parameter of all requests sent by the client to the server.  The
+  # CGI::Session class in conjunction with the CGI class will transparently
+  # add the session id as a hidden input field to all forms generated
+  # using the CGI#form() HTML generation method.  No built-in support is
+  # provided for other mechanisms, such as URL re-writing.  The caller is
+  # responsible for extracting the session id from the session_id 
+  # attribute and manually encoding it in URLs and adding it as a hidden
+  # input to HTML forms created by other mechanisms.  Also, session expiry
+  # is not automatically handled.
+  #
+  # == Examples of use
+  #
+  # === Setting the user's name
+  #
+  #   require 'cgi'
+  #   require 'cgi/session'
+  #   require 'cgi/session/pstore'     # provides CGI::Session::PStore
+  #
+  #   cgi = CGI.new("html4")
+  #
+  #   session = CGI::Session.new(cgi,
+  #       'database_manager' => CGI::Session::PStore,  # use PStore
+  #       'session_key' => '_rb_sess_id',              # custom session key
+  #       'session_expires' => Time.now + 30 * 60,     # 30 minute timeout 
+  #       'prefix' => 'pstore_sid_')                   # PStore option
+  #   if cgi.has_key?('user_name') and cgi['user_name'] != ''
+  #       # coerce to String: cgi[] returns the 
+  #       # string-like CGI::QueryExtension::Value
+  #       session['user_name'] = cgi['user_name'].to_s
+  #   elsif !session['user_name']
+  #       session['user_name'] = "guest"
+  #   end
+  #   session.close
+  #
+  # === Creating a new session safely
+  #
+  #   require 'cgi'
+  #   require 'cgi/session'
+  #
+  #   cgi = CGI.new("html4")
+  #
+  #   # We make sure to delete an old session if one exists,
+  #   # not just to free resources, but to prevent the session 
+  #   # from being maliciously hijacked later on.
+  #   begin
+  #       session = CGI::Session.new(cgi, 'new_session' => false)      
+  #       session.delete                 
+  #   rescue ArgumentError  # if no old session
+  #   end
+  #   session = CGI::Session.new(cgi, 'new_session' => true)
+  #   session.close
+  #
   class Session
 
+    # The id of this session.
     attr_reader :session_id
 
-    def Session::callback(dbman)
+    def Session::callback(dbman)  #:nodoc:
       lambda{
 	dbman[0].close unless dbman.empty?
       }
     end
 
+    # Create a new session id.
+    #
+    # The session id is an MD5 hash based upon the time,
+    # a random number, and a constant string.  This routine
+    # is used internally for automatically generated
+    # session ids. 
     def Session::create_new_id
       require 'digest/md5'
       md5 = Digest::MD5::new
@@ -26,6 +180,62 @@ class CGI
       md5.hexdigest[0,16]
     end
 
+    # Create a new CGI::Session object for +request+.
+    #
+    # +request+ is an instance of the +CGI+ class (see cgi.rb).
+    # +option+ is a hash of options for initialising this
+    # CGI::Session instance.  The following options are
+    # recognised:
+    #
+    # session_key:: the parameter name used for the session id.
+    #               Defaults to '_session_id'.
+    # session_id:: the session id to use.  If not provided, then
+    #              it is retrieved from the +session_key+ parameter
+    #              of the request, or automatically generated for
+    #              a new session.
+    # new_session:: if true, force creation of a new session.  If not set, 
+    #               a new session is only created if none currently
+    #               exists.  If false, a new session is never created,
+    #               and if none currently exists and the +session_id+
+    #               option is not set, an ArgumentError is raised.
+    # database_manager:: the name of the class providing storage facilities
+    #                    for session state persistence.  Built-in support
+    #                    is provided for +FileStore+ (the default),
+    #                    +MemoryStore+, and +PStore+ (from
+    #                    cgi/session/pstore.rb).  See the documentation for
+    #                    these classes for more details.
+    #
+    # The following options are also recognised, but only apply if the
+    # session id is stored in a cookie.
+    #
+    # session_expires:: the time the current session expires, as a 
+    #                   +Time+ object.  If not set, the session will continue
+    #                   indefinitely.
+    # session_domain:: the hostname domain for which this session is valid.
+    #                  If not set, defaults to the hostname of the server.
+    # session_secure:: if +true+, this session will only work over HTTPS.
+    # session_path:: the path for which this session applies.  Defaults
+    #                to the directory of the CGI script.
+    #
+    # +option+ is also passed on to the session storage class initialiser; see
+    # the documentation for each session storage class for the options
+    # they support.
+    #                  
+    # The retrieved or created session is automatically added to +request+
+    # as a cookie, and also to its +output_hidden+ table, which is used
+    # to add hidden input elements to forms.  
+    #
+    # *WARNING* the +output_hidden+
+    # fields are surrounded by a <fieldset> tag in HTML 4 generation, which
+    # is _not_ invisible on many browsers; you may wish to disable the
+    # use of fieldsets with code similar to the following
+    # (see http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-list/37805)
+    #
+    #   cgi = CGI.new("html4")
+    #   class << cgi
+    #       undef_method :fieldset
+    #   end
+    #
     def initialize(request, option={})
       session_key = option['session_key'] || '_session_id'
       id = option['session_id']
@@ -73,6 +283,7 @@ class CGI
       ObjectSpace::define_finalizer(self, Session::callback(@dbprot))
     end
 
+    # Retrieve the session data for key +key+.
     def [](key)
       unless @data
 	@data = @dbman.restore
@@ -80,6 +291,7 @@ class CGI
       @data[key]
     end
 
+    # Set the session date for key +key+.
     def []=(key, val)
       unless @write_lock
 	@write_lock = true
@@ -90,25 +302,61 @@ class CGI
       @data[key] = val
     end
 
-    def update
+    # Store session data on the server.  For some session storage types,
+    # this is a no-op.
+    def update  
       @dbman.update
     end
 
+    # Store session data on the server and close the session storage.  
+    # For some session storage types, this is a no-op.
     def close
       @dbman.close
       @dbprot.clear
     end
 
+    # Delete the session from storage.  Also closes the storage.
+    #
+    # Note that the session's data is _not_ automatically deleted
+    # upon the session expiring.
     def delete
       @dbman.delete
       @dbprot.clear
     end
 
+    # File-based session storage class.
+    #
+    # Implements session storage as a flat file of 'key=value' values.
+    # This storage type only works directly with String values; the
+    # user is responsible for converting other types to Strings when
+    # storing and from Strings when retrieving.
     class FileStore
-      def check_id(id)
+      def check_id(id) #:nodoc:
 	/[^0-9a-zA-Z]/ =~ id.to_s ? false : true
       end
 
+      # Create a new FileStore instance.
+      #
+      # This constructor is used internally by CGI::Session.  The
+      # user does not generally need to call it directly.
+      #
+      # +session+ is the session for which this instance is being
+      # created.  The session id must only contain alphanumeric
+      # characters; automatically generated session ids observe
+      # this requirement.
+      # 
+      # +option+ is a hash of options for the initialiser.  The
+      # following options are recognised:
+      #
+      # tmpdir:: the directory to use for storing the FileStore
+      #          file.  Defaults to Dir::tmpdir (generally "/tmp"
+      #          on Unix systems).
+      # prefix:: the prefix to add to the session id when generating
+      #          the filename for this session's FileStore file.
+      #          Defaults to the empty string.
+      #
+      # This session's FileStore file will be created if it does
+      # not exist, or opened if it does.
       def initialize(session, option={})
 	dir = option['tmpdir'] || Dir::tmpdir
 	prefix = option['prefix'] || ''
@@ -128,6 +376,9 @@ class CGI
 	end
       end
 
+      # Restore session state from the session's FileStore file.
+      #
+      # Returns the session state as a hash.
       def restore
 	unless @hash
 	  @hash = {}
@@ -142,6 +393,7 @@ class CGI
 	@hash
       end
 
+      # Save session state to the session's FileStore file.
       def update
 	return unless @hash
 	@f.rewind
@@ -151,12 +403,14 @@ class CGI
 	@f.truncate @f.tell
       end
 
+      # Update and close the session's FileStore file.
       def close
 	return if @f.closed?
 	update
 	@f.close
       end
 
+      # Close and delete the session's FileStore file.
       def delete
 	path = @f.path
 	@f.close
@@ -164,26 +418,46 @@ class CGI
       end
     end
 
+    # In-memory session storage class.
+    #
+    # Implements session storage as a global in-memory hash.  Session
+    # data will only persist for as long as the ruby interpreter 
+    # instance does.
     class MemoryStore
-      GLOBAL_HASH_TABLE = {}
+      GLOBAL_HASH_TABLE = {} #:nodoc:
 
+      # Create a new MemoryStore instance.
+      #
+      # +session+ is the session this instance is associated with.
+      # +option+ is a list of initialisation options.  None are
+      # currently recognised.
       def initialize(session, option=nil)
 	@session_id = session.session_id
 	GLOBAL_HASH_TABLE[@session_id] ||= {}
       end
 
+      # Restore session state.
+      #
+      # Returns session data as a hash.
       def restore
 	GLOBAL_HASH_TABLE[@session_id]
       end
 
+      # Update session state.
+      #
+      # A no-op.
       def update
 	# don't need to update; hash is shared
       end
 
+      # Close session storage.
+      #
+      # A no-op.
       def close
 	# don't need to close
       end
 
+      # Delete the session state.
       def delete
 	GLOBAL_HASH_TABLE.delete(@session_id)
       end