;;; url-cache.el --- Uniform Resource Locator retrieval tool -*- lexical-binding: t; -*-
;; Copyright (C) 1996-1999, 2004-2024 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 of the License, 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. If not, see <https://www.gnu.org/licenses/>.
;;; Commentary:
;;; Code:
(require 'url-parse)
(require 'url-util)
(require 'url) ;E.g. for url-configuration-directory.
(defcustom url-cache-directory
(expand-file-name "cache" url-configuration-directory)
"The directory where cache files should be stored."
:type 'directory
:group 'url-file)
(defcustom url-cache-expire-time 3600
"Default maximum time in seconds before cache files expire.
Used by the function `url-cache-expired'."
:version "24.1"
:type 'natnum
:group 'url-cache)
;; Cache manager
(defun url-cache-file-writable-p (file)
"Follows the documentation of `file-writable-p', unlike `file-writable-p'."
(and (file-writable-p file)
(if (file-exists-p file)
(not (file-directory-p file))
(file-directory-p (file-name-directory file)))))
(defun url-cache-prepare (file)
"Make it possible to cache data in FILE.
Creates any necessary parent directories, deleting any non-directory files
that would stop this. Returns nil if parent directories can not be
created. If FILE already exists as a non-directory, it changes
permissions of FILE or deletes FILE to make it possible to write a new
version of FILE. Returns nil if this can not be done, or if FILE already
exists as a directory. Otherwise, returns t, indicating that
FILE can be created or overwritten."
(cond
((url-cache-file-writable-p file)
t)
((file-directory-p file)
nil)
(t
(condition-case ()
(or (make-directory (file-name-directory file) t) t)
(error nil)))))
;;;###autoload
(defun url-store-in-cache (&optional buff)
"Store buffer BUFF in the cache."
(with-current-buffer (get-buffer (or buff (current-buffer)))
(let ((fname (url-cache-create-filename (url-view-url t))))
(if (url-cache-prepare fname)
(let ((coding-system-for-write 'binary))
(write-region (point-min) (point-max) fname nil 5))))))
(defun url-fetch-from-cache (url)
"Fetch URL from cache and return a buffer with the content."
(with-current-buffer (generate-new-buffer " *temp*")
(url-cache-extract (url-cache-create-filename url))
(current-buffer)))
;;;###autoload
(defun url-is-cached (url)
"Return non-nil if the URL is cached.
The actual return value is the last modification time of the cache file."
(let* ((fname (url-cache-create-filename url))
(attribs (file-attributes fname)))
(and fname
(file-exists-p fname)
(not (eq (file-attribute-type attribs) t))
(file-attribute-modification-time attribs))))
(defun url-cache-create-filename-human-readable (url)
"Return a filename in the local cache for URL."
(if url
(let* ((urlobj (url-generic-parse-url url))
(protocol (url-type urlobj))
(hostname (url-host urlobj))
(host-components
(cons
(user-real-login-name)
(cons (or protocol "file")
(reverse (split-string (or hostname "localhost")
"\\.")))))
(fname (url-filename urlobj)))
(if (and fname (/= (length fname) 0) (= (aref fname 0) ?/))
(setq fname (substring fname 1 nil)))
(if fname
(let ((slash nil))
(setq fname
(mapconcat
(lambda (x)
(cond
((and (= ?/ x) slash)
(setq slash nil)
"%2F")
((= ?/ x)
(setq slash t)
"/")
(t
(setq slash nil)
(char-to-string x)))) fname ""))))
(setq fname (and fname
(mapconcat
(lambda (x)
(if (= x ?~) "" (char-to-string x)))
fname ""))
fname (cond
((null fname) nil)
((or (string= "" fname) (string= "/" fname))
url-directory-index-file)
((= (string-to-char fname) ?/)
(if (string= (substring fname -1 nil) "/")
(concat fname url-directory-index-file)
(substring fname 1 nil)))
(t
(if (string= (substring fname -1 nil) "/")
(concat fname url-directory-index-file)
fname))))
(and fname
(expand-file-name fname
(expand-file-name
(mapconcat 'identity host-components "/")
url-cache-directory))))))
(defun url-cache-create-filename-using-md5 (url)
"Create a cached filename using MD5.
Very fast if you have an `md5' primitive function, suitably fast otherwise."
(if url
(let* ((checksum (md5 url))
(urlobj (url-generic-parse-url url))
(protocol (url-type urlobj))
(hostname (url-host urlobj))
(host-components
(cons
(user-real-login-name)
(cons (or protocol "file")
(nreverse
(delq nil
(split-string (or hostname "localhost")
"\\."))))))
(fname (url-filename urlobj)))
(and fname
(expand-file-name checksum
(expand-file-name
(mapconcat 'identity host-components "/")
url-cache-directory))))))
(defcustom url-cache-creation-function 'url-cache-create-filename-using-md5
"What function to use to create a cached filename."
:type '(choice (const :tag "MD5 of filename (low collision rate)"
:value url-cache-create-filename-using-md5)
(const :tag "Human readable filenames (higher collision rate)"
:value url-cache-create-filename-human-readable)
(function :tag "Other"))
:group 'url-cache)
(defun url-cache-create-filename (url)
(funcall url-cache-creation-function
;; We need to parse+recreate in order to remove the default port
;; if it has been specified: e.g. http://www.example.com:80 will
;; be transcoded as http://www.example.com
(url-recreate-url
(if (url-p url) url
(url-generic-parse-url url)))))
;;;###autoload
(defun url-cache-extract (fnam)
"Extract FNAM from the local disk cache."
(erase-buffer)
(set-buffer-multibyte nil)
(insert-file-contents-literally fnam))
(defun url-cache-expired (url &optional expire-time)
"Return non-nil if a cached URL is older than EXPIRE-TIME seconds.
The default value of EXPIRE-TIME is `url-cache-expire-time'.
If `url-standalone-mode' is non-nil, cached items never expire."
(if url-standalone-mode
(not (file-exists-p (url-cache-create-filename url)))
(let ((cache-time (url-is-cached url)))
(or (not cache-time)
(time-less-p
(time-add
cache-time
(or expire-time url-cache-expire-time))
nil)))))
(defun url-cache-prune-cache (&optional directory)
"Remove all expired files from the cache.
`url-cache-expire-time' says how old a file has to be to be
considered \"expired\"."
(let ((now (current-time))
(total-files 0)
(deleted-files 0))
(setq directory (or directory url-cache-directory))
(when (file-exists-p directory)
(dolist (file (directory-files directory t))
(unless (member (file-name-nondirectory file) '("." ".."))
(setq total-files (1+ total-files))
(cond
((file-directory-p file)
(when (url-cache-prune-cache file)
(setq deleted-files (1+ deleted-files))))
((time-less-p
(time-add
(file-attribute-modification-time (file-attributes file))
url-cache-expire-time)
now)
(delete-file file)
(setq deleted-files (1+ deleted-files))))))
(if (< deleted-files total-files)
nil
(delete-directory directory)
t))))
(provide 'url-cache)
;;; url-cache.el ends here