[Orgmode] [PATCH] sha1 hash of latex fragments to avoid regeneration

[Eric Schulte]

Hi,

The attached patch changes the latex fragment image generation so that
it saves images into files named by the sha1 hash of the latex source
code.  By checking for the existence of image files before image
generation the regeneration of identical images is avoided.

In practice I find that this greatly speeds up export to html and the
`org-preview-latex-fragment' command.

Cheers -- Eric

>From 13e1c48fa6cac43b0c87ca0fbc8e349f7a9fa864 Mon Sep 17 00:00:00 2001
From: Eric Schulte <address@hidden>
Date: Sun, 15 Nov 2009 17:00:09 -0700
Subject: [PATCH] latex fragment images cached using sha1 hash keys

  Latex fragment images are now saved in files named by the sha1 hash
  of the latex text used to create the image.  By checking if files
  exist before images generation the regeneration of identical latex
  images is avoided.
---
 lisp/ChangeLog |    6 ++++++
 lisp/org.el    |   18 +++++++-----------
 2 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 339f248..f18755c 100755
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,9 @@
+2009-11-16  Eric Schulte  <address@hidden>
+
+       * org.el (org-format-latex): Latex images are now saved to files
+       named by the sha1 hash of the latex source text avoiding
+       regeneration of identical images.
+
 2009-11-15  Carsten Dominik  <address@hidden>
 
        * org-wl.el (org-wl-store-link): Handle the case that
diff --git a/lisp/org.el b/lisp/org.el
index bf6573b..46348fc 100644
--- a/lisp/org.el
+++ b/lisp/org.el
@@ -14550,15 +14550,9 @@ Some of the options can be changed using the variable
         (opt org-format-latex-options)
         (matchers (plist-get opt :matchers))
         (re-list org-latex-regexps)
-        (cnt 0) txt link beg end re e checkdir
+        (cnt 0) txt hash link beg end re e checkdir
         executables-checked
         m n block linkfile movefile ov)
-    ;; Check if there are old images files with this prefix, and remove them
-    (when (file-directory-p todir)
-      (mapc 'delete-file
-           (directory-files
-            todir 'full
-            (concat (regexp-quote prefixnodir) "_[0-9]+\\.png$"))))
     ;; Check the different regular expressions
     (while (setq e (pop re-list))
       (setq m (car e) re (nth 1 e) n (nth 2 e)
@@ -14576,9 +14570,10 @@ Some of the options can be changed using the variable
            (setq txt (match-string n)
                  beg (match-beginning n) end (match-end n)
                  cnt (1+ cnt)
-                 linkfile (format "%s_%04d.png" prefix cnt)
-                 movefile (format "%s_%04d.png" absprefix cnt)
                  link (concat block "[[file:" linkfile "]]" block))
+            (setq hash (sha1 txt)
+                 linkfile (format "%s_%s.png" prefix hash)
+                 movefile (format "%s_%s.png" absprefix hash))
            (if msg (message msg cnt))
            (goto-char beg)
            (unless checkdir ; make sure the directory exists
@@ -14592,8 +14587,9 @@ Some of the options can be changed using the variable
               "dvipng" "needed to convert LaTeX fragments to images")
              (setq executables-checked t))
 
-           (org-create-formula-image
-            txt movefile opt forbuffer)
+            (unless (file-exists-p movefile)
+              (org-create-formula-image
+               txt movefile opt forbuffer))
            (if overlays
                (progn
                  (mapc (lambda (o)
-- 
1.6.4.73.gc144