URL decoding

URL decoding is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

This task (the reverse of URL encoding) is to provide a function or mechanism to convert a url-encoded string into its original unencoded form.

Example

The encoded string "http%3A%2F%2Ffoo%20bar%2F" should be reverted to the unencoded form "http://foo bar/".

J

J does not have a native urldecode (until version 7 when jhs includes a jurldecode).

Here is an implementation:

<lang j>require'strings convert' urldecode=: rplc&(;"_1&a."2(,:tolower)'%',.hfd i.#a.)</lang>

Example use:

<lang j> urldecode 'http%3A%2F%2Ffoo%20bar%2F' http://foo bar/</lang>

Note that a minor efficiency improvement is possible, by eliminating duplicated escape codes: <lang j>urldecode=: rplc&(~.,/;"_1&a."2(,:tolower)'%',.hfd i.#a.)</lang>

PureBasic

<lang PureBasic>URL$ = URLDecoder("http%3A%2F%2Ffoo%20bar%2F")

Debug URL$  ; http://foo bar/</lang>

Retro

This is provided by the casket library (used for web app development).

<lang Retro>create buffer 32000 allot

{{

 create bit 5 allot
 : extract  ( $c-$a ) drop @+ bit ! @+ bit 1+ ! bit ;
 : render   ( $c-$n )
   dup '+ = [ drop 32 ] ifTrue
   dup 13 = [ drop 32 ] ifTrue
   dup 10 = [ drop 32 ] ifTrue
   dup '% = [ extract hex toNumber decimal ] ifTrue ;
 : <decode> (  $-$  ) repeat @+ 0; render ^buffer'add again ;

---reveal---

 : decode   (  $-   ) buffer ^buffer'set <decode> drop ;

}}

"http%3A%2F%2Ffoo%20bar%2F" decode buffer puts</lang>