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Store content hashes and timestamps for emacswiki files to minimise requests

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If we can determine whether an emacswiki .el file has changed since
the last download, we can usually skip the follow-up request to
determine its last-modified timestamp.
This commit is contained in:
Steve Purcell 2012-12-04 20:26:25 +00:00
parent 00989cef16
commit 00236212d1
1 changed files with 22 additions and 5 deletions
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27
package-build.el
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@ -178,11 +178,28 @@ seconds; the server cuts off after 10 requests in 20 seconds.")
(url-copy-file download-url filename t))
(when (zerop (nth 7 (file-attributes filename)))
(error "Wiki file %s was empty - has it been removed?" filename))
(with-current-buffer (pb/with-wiki-rate-limit
(url-retrieve-synchronously wiki-url))
(message (format "%s\n" download-url))
(pb/find-parse-time
"Last edited \\([0-9]\\{4\\}-[0-9]\\{2\\}-[0-9]\\{2\\} [0-9]\\{2\\}:[0-9]\\{2\\} [A-Z]\\{3\\}\\)"))))
;; The Last-Modified response header for the download is actually
;; correct for the file, but we have no access to that
;; header. Instead, we must query the non-raw emacswiki page for
;; the file.
;; Since those Emacswiki lookups are time-consuming, we maintain a
;; foo.el.stamp file containing ("SHA1" . "PARSED_TIME")
(let* ((new-content-hash (secure-hash 'sha1 (pb/slurp-file filename)))
(stamp-file (concat filename ".stamp"))
(stamp-info (pb/read-from-file stamp-file)))
(if (eq new-content-hash (car stamp-info))
;; File has not changed, so return old timestamp
(progn
(message "%s is unchanged" filename)
(cdr stamp-info))
(message "%s has changed - checking mod time" filename)
(let ((new-timestamp
(with-current-buffer (pb/with-wiki-rate-limit
(url-retrieve-synchronously wiki-url))
(pb/find-parse-time
"Last edited \\([0-9]\\{4\\}-[0-9]\\{2\\}-[0-9]\\{2\\} [0-9]\\{2\\}:[0-9]\\{2\\} [A-Z]\\{3\\}\\)"))))
(pb/dump (cons new-content-hash new-timestamp) stamp-file)
new-timestamp)))))
(defun pb/checkout-wiki (name config dir)
"Checkout package NAME with config CONFIG from the EmacsWiki into DIR."