lisp/url/url-methods.el

   1 ;;; url-methods.el --- Load URL schemes as needed
   2
   3 ;; Copyright (C) 1996-1999, 2004-2016 Free Software Foundation, Inc.
   4
   5 ;; Keywords: comm, data, processes, hypermedia
   6
   7 ;; This file is part of GNU Emacs.
   8
   9 ;; GNU Emacs is free software: you can redistribute it and/or modify
  10 ;; it under the terms of the GNU General Public License as published by
  11 ;; the Free Software Foundation, either version 3 of the License, or
  12 ;; (at your option) any later version.
  13
  14 ;; GNU Emacs is distributed in the hope that it will be useful,
  15 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  16 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17 ;; GNU General Public License for more details.
  18
  19 ;; You should have received a copy of the GNU General Public License
  20 ;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
  21
  22 ;;; Commentary:
  23
  24 ;;; Code:
  25
  26 ;; This loads up some of the small, silly URLs that I really don't
  27 ;; want to bother putting in their own separate files.
  28 (require 'url-parse)
  29
  30 (defvar url-scheme-registry (make-hash-table :size 7 :test 'equal))
  31
  32 (defconst url-scheme-methods
  33   '((default-port      . variable)
  34     (asynchronous-p    . variable)
  35     (expand-file-name  . function)
  36     (file-exists-p     . function)
  37     (file-attributes   . function)
  38     (parse-url         . function)
  39     (file-symlink-p    . function)
  40     (file-writable-p   . function)
  41     (file-directory-p  . function)
  42     (file-executable-p . function)
  43     (directory-files   . function)
  44     (file-truename     . function))
  45   "Assoc-list of methods that each URL loader can provide.")
  46
  47 (defconst url-scheme-default-properties
  48   (list 'name "unknown"
  49         'loader 'url-scheme-default-loader
  50         'default-port 0
  51         'expand-file-name 'url-identity-expander
  52         'parse-url 'url-generic-parse-url
  53         'asynchronous-p nil
  54         'file-directory-p 'ignore
  55         'file-truename (lambda (&rest args)
  56                          (url-recreate-url (car args)))
  57         'file-exists-p 'ignore
  58         'file-attributes 'ignore))
  59
  60 (defun url-scheme-default-loader (url &optional callback cbargs)
  61   "Signal an error for an unknown URL scheme."
  62   (error "Unknown URL scheme: %s" (url-type url)))
  63
  64 (defvar url-scheme--registering-proxy nil)
  65
  66 (defun url-scheme-register-proxy (scheme)
  67   "Automatically find a proxy for SCHEME and put it in `url-proxy-services'."
  68   (let* ((env-var (concat scheme "_proxy"))
  69          (env-proxy (or (getenv (upcase env-var))
  70                         (getenv (downcase env-var))))
  71          (cur-proxy (assoc scheme url-proxy-services))
  72          (urlobj nil)
  73          (url-scheme--registering-proxy t))
  74
  75     ;; If env-proxy is an empty string, treat it as if it were nil
  76     (when (and (stringp env-proxy)
  77                (string= env-proxy ""))
  78       (setq env-proxy nil))
  79
  80     ;; Store any proxying information - this will not overwrite an old
  81     ;; entry, so that people can still set this information in their
  82     ;; init file
  83     (cond
  84      (cur-proxy nil)                    ; Keep their old settings
  85      ((null env-proxy) nil)             ; No proxy setup
  86      ;; First check if its something like hostname:port
  87      ((string-match "^\\([^:]+\\):\\([0-9]+\\)$" env-proxy)
  88       (setq urlobj (url-generic-parse-url nil)) ; Get a blank object
  89       (setf (url-type urlobj) "http")
  90       (setf (url-host urlobj) (match-string 1 env-proxy))
  91       (setf (url-port urlobj) (string-to-number (match-string 2 env-proxy))))
  92      ;; Then check if its a fully specified URL
  93      ((string-match url-nonrelative-link env-proxy)
  94       (setq urlobj (url-generic-parse-url env-proxy))
  95       (setf (url-type urlobj) "http")
  96       (setf (url-target urlobj) nil))
  97      ;; Finally, fall back on the assumption that its just a hostname
  98      (t
  99       (setq urlobj (url-generic-parse-url nil)) ; Get a blank object
 100       (setf (url-type urlobj) "http")
 101       (setf (url-host urlobj) env-proxy)))
 102
 103      (if (and (not cur-proxy) urlobj)
 104          (progn
 105            (setq url-proxy-services
 106                  (cons (cons scheme (format "%s:%d" (url-host urlobj)
 107                                             (url-port urlobj)))
 108                        url-proxy-services))
 109            (message "Using a proxy for %s..." scheme)))))
 110
 111 (defun url-scheme-get-property (scheme property)
 112   "Get PROPERTY of a URL SCHEME.
 113 Will automatically try to load a backend from url-SCHEME.el if
 114 it has not already been loaded."
 115   (setq scheme (downcase scheme))
 116   (let ((desc (gethash scheme url-scheme-registry)))
 117     (if (not desc)
 118         (let* ((stub (concat "url-" scheme))
 119                (loader (intern stub)))
 120           (condition-case ()
 121               ;; url-https.el was merged into url-http because of 8+3
 122               ;; filename limitations, so we have to do this dance.
 123               (require (if (equal "https" scheme) 'url-http loader))
 124             (error nil))
 125           (if (fboundp loader)
 126               (progn
 127                 ;; Found the module to handle <scheme> URLs
 128                 (unless url-scheme--registering-proxy
 129                   (url-scheme-register-proxy scheme))
 130                 (setq desc (list 'name scheme
 131                                  'loader loader))
 132                 (dolist (cell url-scheme-methods)
 133                   (let ((symbol (intern-soft (format "%s-%s" stub (car cell))))
 134                         (type (cdr cell)))
 135                     (if symbol
 136                         (pcase type
 137                           (`function
 138                            ;; Store the symbol name of a function
 139                            (if (fboundp symbol)
 140                                (setq desc (plist-put desc (car cell) symbol))))
 141                           (`variable
 142                            ;; Store the VALUE of a variable
 143                            (if (boundp symbol)
 144                                (setq desc (plist-put desc (car cell)
 145                                                      (symbol-value symbol)))))
 146                           (_
 147                            (error "Malformed url-scheme-methods entry: %S"
 148                                   cell))))))
 149                 (puthash scheme desc url-scheme-registry)))))
 150     (or (plist-get desc property)
 151         (plist-get url-scheme-default-properties property))))
 152
 153 (provide 'url-methods)
 154
 155 ;;; url-methods.el ends here