Re: URL decoding function in C++/C?

From:
 James Kanze <james.kanze@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Mon, 11 Jun 2007 02:41:26 -0700
Message-ID:
<1181554886.046249.214580@k79g2000hse.googlegroups.com>
On Jun 11, 8:21 am, "Robbie Hatley" <bogus.addr...@no.spam> wrote:

Herman Schultz wrote:

Can you please tell me if there is a library function
in C++/C to do URL decoding?
i.e. change from:
http%3A%2F%2F
to:
http://


There is no *standard* library facility to do that.

There's almost certainly libraries out there that have
that facility, though. Google for "C++ URL library" or
similar searches.

However, it may be simpler to just to write your own.


You're kidding, of course.

Here's a big hint: Unix file names may only contain certain
characters, not others;


It has nothing to do with Unix; the only characters which cannot
occur in a Unix filename are '/' and '\0'.

    [...]

Grab each "%XY" using std::string.find() and std::string.substr().
Feed each "%XY" substring into a function that returns the
character with that encoding. Then replace the "%XY" in the string
with the character Z which you just generated, by using
std::string.replace().


And this is simpler than just calling a single function in a
third party library.

Here's a program I just wrote, for the fun of it, which solves
your problem (tested, working code). (CAVEAT: This assumes that
any '%' character will be followed by a valid two-digit hexidecimal
number. If not, it will blow up. You'll have to add your own
error-checking.)


Which will likely increase the size of the code by two or three.

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