root/trunk/lisp/url/url-methods.el

;;; url-methods.el --- Load URL schemes as needed

;; Copyright (C) 1996, 1997, 1998, 1999, 2004,
;;   2005, 2006, 2007, 2008 Free Software Foundation, Inc.

;; Keywords: comm, data, processes, hypermedia

;; This file is part of GNU Emacs.

;; GNU Emacs is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation; either version 3, or (at your option)
;; any later version.
;;
;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT 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
;; along with GNU Emacs; see the file COPYING.  If not, write to the
;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
;; Boston, MA 02110-1301, USA.

;;; Commentary:

;;; Code:

(eval-when-compile
  (require 'cl))

;; This loads up some of the small, silly URLs that I really don't
;; want to bother putting in their own separate files.
(require 'url-parse)

(defvar url-scheme-registry (make-hash-table :size 7 :test 'equal))

(defconst url-scheme-methods
  '((default-port      . variable)
    (asynchronous-p    . variable)
    (expand-file-name  . function)
    (file-exists-p     . function)
    (file-attributes   . function)
    (parse-url         . function)
    (file-symlink-p    . function)
    (file-writable-p   . function)
    (file-directory-p  . function)
    (file-executable-p . function)
    (directory-files   . function)
    (file-truename     . function))
  "Assoc-list of methods that each URL loader can provide.")

(defconst url-scheme-default-properties
  (list 'name "unknown"
        'loader 'url-scheme-default-loader
        'default-port 0
        'expand-file-name 'url-identity-expander
        'parse-url 'url-generic-parse-url
        'asynchronous-p nil
        'file-directory-p 'ignore
        'file-truename (lambda (&rest args)
                         (url-recreate-url (car args)))
        'file-exists-p 'ignore
        'file-attributes 'ignore))

(defun url-scheme-default-loader (url &optional callback cbargs)
  "Signal an error for an unknown URL scheme."
  (error "Unkown URL scheme: %s" (url-type url)))

(defun url-scheme-register-proxy (scheme)
  "Automatically find a proxy for SCHEME and put it in `url-proxy-services'."
  (let* ((env-var (concat scheme "_proxy"))
         (env-proxy (or (getenv (upcase env-var))
                        (getenv (downcase env-var))))
         (cur-proxy (assoc scheme url-proxy-services))
         (urlobj nil))

    ;; If env-proxy is an empty string, treat it as if it were nil
    (when (and (stringp env-proxy)
               (string= env-proxy ""))
      (setq env-proxy nil))

    ;; Store any proxying information - this will not overwrite an old
    ;; entry, so that people can still set this information in their
    ;; .emacs file
    (cond
     (cur-proxy nil)                    ; Keep their old settings
     ((null env-proxy) nil)             ; No proxy setup
     ;; First check if its something like hostname:port
     ((string-match "^\\([^:]+\\):\\([0-9]+\\)$" env-proxy)
      (setq urlobj (url-generic-parse-url nil)) ; Get a blank object
      (url-set-type urlobj "http")
      (url-set-host urlobj (match-string 1 env-proxy))
      (url-set-port urlobj (string-to-number (match-string 2 env-proxy))))
     ;; Then check if its a fully specified URL
     ((string-match url-nonrelative-link env-proxy)
      (setq urlobj (url-generic-parse-url env-proxy))
      (url-set-type urlobj "http")
      (url-set-target urlobj nil))
     ;; Finally, fall back on the assumption that its just a hostname
     (t
      (setq urlobj (url-generic-parse-url nil)) ; Get a blank object
      (url-set-type urlobj "http")
      (url-set-host urlobj env-proxy)))

     (if (and (not cur-proxy) urlobj)
         (progn
           (setq url-proxy-services
                 (cons (cons scheme (format "%s:%d" (url-host urlobj)
                                            (url-port urlobj)))
                       url-proxy-services))
           (message "Using a proxy for %s..." scheme)))))

(defun url-scheme-get-property (scheme property)
  "Get property of a URL SCHEME.
Will automatically try to load a backend from url-SCHEME.el if
it has not already been loaded."
  (setq scheme (downcase scheme))
  (let ((desc (gethash scheme url-scheme-registry)))
    (if (not desc)
        (let* ((stub (concat "url-" scheme))
               (loader (intern stub)))
          (condition-case ()
              (require loader)
            (error nil))
          (if (fboundp loader)
              (progn
                ;; Found the module to handle <scheme> URLs
                (url-scheme-register-proxy scheme)
                (setq desc (list 'name scheme
                                 'loader loader))
                (dolist (cell url-scheme-methods)
                  (let ((symbol (intern-soft (format "%s-%s" stub (car cell))))
                        (type (cdr cell)))
                    (if symbol
                        (case type
                          (function
                           ;; Store the symbol name of a function
                           (if (fboundp symbol)
                               (setq desc (plist-put desc (car cell) symbol))))
                          (variable
                           ;; Store the VALUE of a variable
                           (if (boundp symbol)
                               (setq desc (plist-put desc (car cell)
                                                     (symbol-value symbol)))))
                          (otherwise
                           (error "Malformed url-scheme-methods entry: %S"
                                  cell))))))
                (puthash scheme desc url-scheme-registry)))))
    (or (plist-get desc property)
        (plist-get url-scheme-default-properties property))))

(provide 'url-methods)

;; arch-tag: 336863f8-5a07-4906-9be5-b3c6bcebbe67
;;; url-methods.el ends here