Re: [bug] org-link-escape and (wrong-type-argument stringp nil)

From: David Maus <dmaus@ictsoc.de>
To: Sebastian Rose <sebastian_rose@gmx.de>
Cc: "David Maus" <dmaus@ictsoc.de>,
	emacs-orgmode@gnu.org,
	"Sébastien Vauban" <wxhgmqzgwmuf@spammotel.com>
Subject: Re: [bug] org-link-escape and (wrong-type-argument stringp	nil)
Date: Thu, 23 Sep 2010 20:40:33 +0200	[thread overview]
Message-ID: <87aan8xpzy.wl%dmaus@ictsoc.de> (raw)
In-Reply-To: <87fwx1yhw5.fsf@gmx.de>


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Sebastian Rose wrote:
>David Maus <dmaus@ictsoc.de> writes:
>> Sebastian Rose wrote:
>>>Is there a reason for this distinction between multibyte and unibyte?
>>>I favour the "shotgun-approach" if not.  It's bullet-proof.
>>
>>>The JavaScript function `encodeURIComponent()' encodes the German Umlaut
>>>`ü' as `%C3%B6' regardless of the sources encoding actually.  That's why
>>>I wrote the two functions `org-protocol-unhex-string' and
>>>`org-protocol-unhex-compound' (s. org-protocol.el).
>>
>> Ah, yes.  From my understandig of the RFC %C3%BC is a valid
>> representation of the "ü" character.  
>>
>> I do not yet fully understand
>> how to unescape such a representation.  E.g. Is %C3%BC a hexencoded
>> multibyte char or a succession of two singlebyte chars?

>It's a hexencoded multibyte char.

>JavaScript implementations seem to turn non-ascii singlebyte chars
>into multibyte chars first, then encode the result.

>This means if a page is iso-8859-1 encoded (singlebyte `ü'),
>JavaScript will recode the `ü'.  It's funny, but that's what I found
>when writing org-protocol.el


>`org-protocol-unhex-string' and `org-protocol-unhex-compound' decode
>such a representation.

>The trick is in the utf-8 encoding itself.  If a byte starts with a 1,
>another byte will follow.  The number of leading `1's denotes the amount
>of bytes used for one character.   On a GNU/Linux system try

>  sh$  man utf-8

Thanks!  I finally get a grip on one of my personal nightmares.  The
attached patch is the first step in this direction: It modifies the
algorithm of `org-link-escape', now iterating over the input string
with `mapconcat' and escaping all characters in the escape table or
are between 127 and 255.

I'll try to figure out the escaping/unescaping of multibyte characters
next.

Sent as a patch because of it's possible side-effects: The new
algorithm ignores the cdr of the escape table cons -- Thus things will
break if they use this function for anything else then percent
escaping.

Best,
  -- David
-- 
OpenPGP... 0x99ADB83B5A4478E6
Jabber.... dmjena@jabber.org
Email..... dmaus@ictsoc.de

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From 8209cb831d0d387d03b10416235d2910a74f80f7 Mon Sep 17 00:00:00 2001
From: David Maus <dmaus@ictsoc.de>
Date: Thu, 23 Sep 2010 20:30:13 +0200
Subject: [PATCH] New algorithm for percent escaping

* org.el (org-link-escape): New algorithm for percent escaping.

Interate over TEXT and replace chars that are in TABLE or are
non-ASCII single byte characters.  Multibyte characters are left
untouched.
---
 lisp/org.el |   16 +++++-----------
 1 files changed, 5 insertions(+), 11 deletions(-)

diff --git a/lisp/org.el b/lisp/org.el
index d7aa3d2..2c3f1b7 100644
--- a/lisp/org.el
+++ b/lisp/org.el
@@ -8491,17 +8491,11 @@ This is the list that is used before handing over to the browser.")
   (if (and org-url-encoding-use-url-hexify (not table))
       (url-hexify-string text)
     (setq table (or table org-link-escape-chars))
-    (when text
-      (let ((re (mapconcat (lambda (x) (regexp-quote
-					(char-to-string (car x))))
-			   table "\\|")))
-	(while (string-match re text)
-	  (setq text
-		(replace-match
-		 (cdr (assoc (string-to-char (match-string 0 text))
-			     table))
-	       t t text)))
-	text))))
+    (mapconcat (lambda (c)
+		 (if (or (assoc c table)
+			 (and (> c 126) (< c 255)))
+		     (format "%%%X" c)
+		   (char-to-string c))) text "")))
 
 (defun org-link-unescape (text &optional table)
   "Reverse the action of `org-link-escape'."
-- 
1.7.1


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