lisp/url/url-cache.el

   1 ;;; url-cache.el --- Uniform Resource Locator retrieval tool
   2
   3 ;; Copyright (C) 1996, 1997, 1998, 1999, 2004,
   4 ;;   2005, 2006, 2007, 2008, 2009, 2010  Free Software Foundation, Inc.
   5
   6 ;; Keywords: comm, data, processes, hypermedia
   7
   8 ;; This file is part of GNU Emacs.
   9
  10 ;; GNU Emacs is free software: you can redistribute it and/or modify
  11 ;; it under the terms of the GNU General Public License as published by
  12 ;; the Free Software Foundation, either version 3 of the License, or
  13 ;; (at your option) any later version.
  14
  15 ;; GNU Emacs is distributed in the hope that it will be useful,
  16 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 ;; GNU General Public License for more details.
  19
  20 ;; You should have received a copy of the GNU General Public License
  21 ;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
  22
  23 ;;; Code:
  24
  25 (require 'url-parse)
  26 (require 'url-util)
  27 (require 'url)                        ;E.g. for url-configuration-directory.
  28
  29 (defcustom url-cache-directory
  30   (expand-file-name "cache" url-configuration-directory)
  31   "*The directory where cache files should be stored."
  32   :type 'directory
  33   :group 'url-file)
  34
  35 ;; Cache manager
  36 (defun url-cache-file-writable-p (file)
  37   "Follows the documentation of `file-writable-p', unlike `file-writable-p'."
  38   (and (file-writable-p file)
  39        (if (file-exists-p file)
  40            (not (file-directory-p file))
  41          (file-directory-p (file-name-directory file)))))
  42
  43 (defun url-cache-prepare (file)
  44   "Makes it possible to cache data in FILE.
  45 Creates any necessary parent directories, deleting any non-directory files
  46 that would stop this.  Returns nil if parent directories can not be
  47 created.  If FILE already exists as a non-directory, it changes
  48 permissions of FILE or deletes FILE to make it possible to write a new
  49 version of FILE.  Returns nil if this can not be done, or if FILE already
  50 exists as a directory.  Otherwise, returns t, indicating that
  51 FILE can be created or overwritten."
  52   (cond
  53    ((url-cache-file-writable-p file)
  54     t)
  55    ((file-directory-p file)
  56     nil)
  57    (t
  58     (condition-case ()
  59         (or (make-directory (file-name-directory file) t) t)
  60       (error nil)))))
  61
  62 ;;;###autoload
  63 (defun url-store-in-cache (&optional buff)
  64   "Store buffer BUFF in the cache."
  65   (if (not (and buff (get-buffer buff)))
  66       nil
  67     (save-current-buffer
  68       (and buff (set-buffer buff))
  69       (let* ((fname (url-cache-create-filename (url-view-url t))))
  70         (if (url-cache-prepare fname)
  71             (let ((coding-system-for-write 'binary))
  72               (write-region (point-min) (point-max) fname nil 5)))))))
  73
  74 ;;;###autoload
  75 (defun url-is-cached (url)
  76   "Return non-nil if the URL is cached."
  77   (let* ((fname (url-cache-create-filename url))
  78          (attribs (file-attributes fname)))
  79     (and fname                          ; got a filename
  80          (file-exists-p fname)          ; file exists
  81          (not (eq (nth 0 attribs) t))   ; Its not a directory
  82          (nth 5 attribs))))             ; Can get last mod-time
  83
  84 (defun url-cache-create-filename-human-readable (url)
  85   "Return a filename in the local cache for URL."
  86   (if url
  87       (let* ((url (if (vectorp url) (url-recreate-url url) url))
  88              (urlobj (url-generic-parse-url url))
  89              (protocol (url-type urlobj))
  90              (hostname (url-host urlobj))
  91              (host-components
  92               (cons
  93                (user-real-login-name)
  94                (cons (or protocol "file")
  95                      (reverse (split-string (or hostname "localhost")
  96                                             (eval-when-compile
  97                                               (regexp-quote ".")))))))
  98              (fname    (url-filename urlobj)))
  99         (if (and fname (/= (length fname) 0) (= (aref fname 0) ?/))
 100             (setq fname (substring fname 1 nil)))
 101         (if fname
 102             (let ((slash nil))
 103               (setq fname
 104                     (mapconcat
 105                      (function
 106                       (lambda (x)
 107                         (cond
 108                          ((and (= ?/ x) slash)
 109                           (setq slash nil)
 110                           "%2F")
 111                          ((= ?/ x)
 112                           (setq slash t)
 113                           "/")
 114                          (t
 115                           (setq slash nil)
 116                           (char-to-string x))))) fname ""))))
 117
 118         (setq fname (and fname
 119                          (mapconcat
 120                           (function (lambda (x)
 121                                       (if (= x ?~) "" (char-to-string x))))
 122                           fname ""))
 123               fname (cond
 124                      ((null fname) nil)
 125                      ((or (string= "" fname) (string= "/" fname))
 126                       url-directory-index-file)
 127                      ((= (string-to-char fname) ?/)
 128                       (if (string= (substring fname -1 nil) "/")
 129                           (concat fname url-directory-index-file)
 130                         (substring fname 1 nil)))
 131                      (t
 132                       (if (string= (substring fname -1 nil) "/")
 133                           (concat fname url-directory-index-file)
 134                         fname))))
 135         (and fname
 136              (expand-file-name fname
 137                                (expand-file-name
 138                                 (mapconcat 'identity host-components "/")
 139                                 url-cache-directory))))))
 140
 141 (defun url-cache-create-filename-using-md5 (url)
 142   "Create a cached filename using MD5.
 143 Very fast if you have an `md5' primitive function, suitably fast otherwise."
 144   (require 'md5)
 145   (if url
 146       (let* ((url (if (vectorp url) (url-recreate-url url) url))
 147              (checksum (md5 url))
 148              (urlobj (url-generic-parse-url url))
 149              (protocol (url-type urlobj))
 150              (hostname (url-host urlobj))
 151              (host-components
 152               (cons
 153                (user-real-login-name)
 154                (cons (or protocol "file")
 155                      (nreverse
 156                       (delq nil
 157                             (split-string (or hostname "localhost")
 158                                           (eval-when-compile
 159                                             (regexp-quote "."))))))))
 160              (fname    (url-filename urlobj)))
 161         (and fname
 162              (expand-file-name checksum
 163                                (expand-file-name
 164                                 (mapconcat 'identity host-components "/")
 165                                 url-cache-directory))))))
 166
 167 (defcustom url-cache-creation-function 'url-cache-create-filename-using-md5
 168   "*What function to use to create a cached filename."
 169   :type '(choice (const :tag "MD5 of filename (low collision rate)"
 170                         :value url-cache-create-filename-using-md5)
 171                  (const :tag "Human readable filenames (higher collision rate)"
 172                         :value url-cache-create-filename-human-readable)
 173                  (function :tag "Other"))
 174   :group 'url-cache)
 175
 176 (defun url-cache-create-filename (url)
 177   (funcall url-cache-creation-function url))
 178
 179 ;;;###autoload
 180 (defun url-cache-extract (fnam)
 181   "Extract FNAM from the local disk cache."
 182   (erase-buffer)
 183   (insert-file-contents-literally fnam))
 184
 185 ;;;###autoload
 186 (defun url-cache-expired (url mod)
 187   "Return t if a cached file has expired."
 188   (let* ((urlobj (if (vectorp url) url (url-generic-parse-url url)))
 189          (type (url-type urlobj)))
 190     (cond
 191      (url-standalone-mode
 192       (not (file-exists-p (url-cache-create-filename url))))
 193      ((string= type "http")
 194       t)
 195      ((member type '("file" "ftp"))
 196       (if (or (equal mod '(0 0)) (not mod))
 197           t
 198         (or (> (nth 0 mod) (nth 0 (current-time)))
 199             (> (nth 1 mod) (nth 1 (current-time))))))
 200      (t nil))))
 201
 202 (provide 'url-cache)
 203
 204 ;; arch-tag: 95b050a6-8e81-4f23-8e63-191b9d1d657c
 205 ;;; url-cache.el ends here