243 lines
8.1 KiB
EmacsLisp
243 lines
8.1 KiB
EmacsLisp
;;; url-cache.el --- Uniform Resource Locator retrieval tool -*- lexical-binding: t; -*-
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;; Copyright (C) 1996-1999, 2004-2024 Free Software Foundation, Inc.
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;; Keywords: comm, data, processes, hypermedia
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;; This file is part of GNU Emacs.
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;; GNU Emacs is free software: you can redistribute it and/or modify
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;; it under the terms of the GNU General Public License as published by
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;; the Free Software Foundation, either version 3 of the License, or
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;; (at your option) any later version.
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;; GNU Emacs is distributed in the hope that it will be useful,
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;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;; GNU General Public License for more details.
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;; You should have received a copy of the GNU General Public License
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;; along with GNU Emacs. If not, see <https://www.gnu.org/licenses/>.
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;;; Commentary:
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;;; Code:
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(require 'url-parse)
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(require 'url-util)
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(require 'url) ;E.g. for url-configuration-directory.
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(defcustom url-cache-directory
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(expand-file-name "cache" url-configuration-directory)
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"The directory where cache files should be stored."
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:type 'directory
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:group 'url-file)
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(defcustom url-cache-expire-time 3600
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"Default maximum time in seconds before cache files expire.
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Used by the function `url-cache-expired'."
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:version "24.1"
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:type 'natnum
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:group 'url-cache)
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;; Cache manager
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(defun url-cache-file-writable-p (file)
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"Follows the documentation of `file-writable-p', unlike `file-writable-p'."
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(and (file-writable-p file)
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(if (file-exists-p file)
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(not (file-directory-p file))
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(file-directory-p (file-name-directory file)))))
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(defun url-cache-prepare (file)
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"Make it possible to cache data in FILE.
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Creates any necessary parent directories, deleting any non-directory files
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that would stop this. Returns nil if parent directories can not be
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created. If FILE already exists as a non-directory, it changes
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permissions of FILE or deletes FILE to make it possible to write a new
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version of FILE. Returns nil if this can not be done, or if FILE already
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exists as a directory. Otherwise, returns t, indicating that
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FILE can be created or overwritten."
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(cond
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((url-cache-file-writable-p file)
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t)
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((file-directory-p file)
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nil)
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(t
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(condition-case ()
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(or (make-directory (file-name-directory file) t) t)
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(error nil)))))
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;;;###autoload
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(defun url-store-in-cache (&optional buff)
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"Store buffer BUFF in the cache."
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(with-current-buffer (or buff (current-buffer))
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(let ((fname (url-cache-create-filename (url-view-url t))))
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(if (url-cache-prepare fname)
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(let ((coding-system-for-write 'binary))
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(write-region (point-min) (point-max) fname nil 5))))))
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(defun url-fetch-from-cache (url)
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"Fetch URL from cache and return a buffer with the content."
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(with-current-buffer (generate-new-buffer " *temp*")
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(url-cache-extract (url-cache-create-filename url))
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(current-buffer)))
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;;;###autoload
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(defun url-is-cached (url)
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"Return non-nil if the URL is cached.
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The actual return value is the last modification time of the cache file."
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(let* ((fname (url-cache-create-filename url))
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(attribs (file-attributes fname)))
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(and fname
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(file-exists-p fname)
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(not (eq (file-attribute-type attribs) t))
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(file-attribute-modification-time attribs))))
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(defun url-cache-create-filename-human-readable (url)
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"Return a filename in the local cache for URL."
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(if url
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(let* ((urlobj (url-generic-parse-url url))
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(protocol (url-type urlobj))
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(hostname (url-host urlobj))
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(host-components
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(cons
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(user-real-login-name)
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(cons (or protocol "file")
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(reverse (split-string (or hostname "localhost")
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"\\.")))))
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(fname (url-filename urlobj)))
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(if (and fname (/= (length fname) 0) (= (aref fname 0) ?/))
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(setq fname (substring fname 1 nil)))
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(if fname
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(let ((slash nil))
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(setq fname
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(mapconcat
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(lambda (x)
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(cond
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((and (= ?/ x) slash)
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(setq slash nil)
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"%2F")
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((= ?/ x)
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(setq slash t)
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"/")
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(t
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(setq slash nil)
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(char-to-string x)))) fname ""))))
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(setq fname (and fname
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(mapconcat
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(lambda (x)
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(if (= x ?~) "" (char-to-string x)))
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fname ""))
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fname (cond
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((null fname) nil)
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((or (string= "" fname) (string= "/" fname))
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url-directory-index-file)
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((= (string-to-char fname) ?/)
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(if (string= (substring fname -1 nil) "/")
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(concat fname url-directory-index-file)
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(substring fname 1 nil)))
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(t
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(if (string= (substring fname -1 nil) "/")
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(concat fname url-directory-index-file)
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fname))))
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(and fname
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(expand-file-name fname
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(expand-file-name
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(mapconcat 'identity host-components "/")
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url-cache-directory))))))
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(defun url-cache-create-filename-using-md5 (url)
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"Create a cached filename using MD5.
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Very fast if you have an `md5' primitive function, suitably fast otherwise."
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(if url
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(let* ((checksum (md5 url))
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(urlobj (url-generic-parse-url url))
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(protocol (url-type urlobj))
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(hostname (url-host urlobj))
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(host-components
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(cons
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(user-real-login-name)
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(cons (or protocol "file")
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(nreverse
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(delq nil
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(split-string (or hostname "localhost")
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"\\."))))))
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(fname (url-filename urlobj)))
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(and fname
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(expand-file-name checksum
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(expand-file-name
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(mapconcat 'identity host-components "/")
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url-cache-directory))))))
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(defcustom url-cache-creation-function 'url-cache-create-filename-using-md5
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"What function to use to create a cached filename."
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:type '(choice (const :tag "MD5 of filename (low collision rate)"
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:value url-cache-create-filename-using-md5)
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(const :tag "Human readable filenames (higher collision rate)"
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:value url-cache-create-filename-human-readable)
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(function :tag "Other"))
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:group 'url-cache)
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(defun url-cache-create-filename (url)
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(funcall url-cache-creation-function
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;; We need to parse+recreate in order to remove the default port
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;; if it has been specified: e.g. http://www.example.com:80 will
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;; be transcoded as http://www.example.com
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(url-recreate-url
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(if (url-p url) url
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(url-generic-parse-url url)))))
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;;;###autoload
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(defun url-cache-extract (fnam)
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"Extract FNAM from the local disk cache."
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(erase-buffer)
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(set-buffer-multibyte nil)
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(insert-file-contents-literally fnam))
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(defun url-cache-expired (url &optional expire-time)
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"Return non-nil if a cached URL is older than EXPIRE-TIME seconds.
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The default value of EXPIRE-TIME is `url-cache-expire-time'.
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If `url-standalone-mode' is non-nil, cached items never expire."
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(if url-standalone-mode
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(not (file-exists-p (url-cache-create-filename url)))
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(let ((cache-time (url-is-cached url)))
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(or (not cache-time)
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(time-less-p
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(time-add
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cache-time
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(or expire-time url-cache-expire-time))
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nil)))))
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(defun url-cache-prune-cache (&optional directory)
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"Remove all expired files from the cache.
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`url-cache-expire-time' says how old a file has to be to be
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considered \"expired\"."
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(let ((now (current-time))
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(total-files 0)
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(deleted-files 0))
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(setq directory (or directory url-cache-directory))
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(when (file-exists-p directory)
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(dolist (file (directory-files directory t))
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(unless (member (file-name-nondirectory file) '("." ".."))
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(setq total-files (1+ total-files))
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(cond
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((file-directory-p file)
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(when (url-cache-prune-cache file)
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(setq deleted-files (1+ deleted-files))))
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((time-less-p
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(time-add
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(file-attribute-modification-time (file-attributes file))
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url-cache-expire-time)
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now)
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(delete-file file)
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(setq deleted-files (1+ deleted-files))))))
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(if (< deleted-files total-files)
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nil
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(delete-directory directory)
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t))))
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(provide 'url-cache)
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;;; url-cache.el ends here
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