src/net/instaweb/util/public/url_escaper.h

/**
 * Copyright 2010 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

// Author: jmarantz@google.com (Joshua Marantz)

#ifndef NET_INSTAWEB_UTIL_PUBLIC_URL_ESCAPER_H_
#define NET_INSTAWEB_UTIL_PUBLIC_URL_ESCAPER_H_

#include "net/instaweb/util/public/url_segment_encoder.h"
#include <string>
#include "net/instaweb/util/public/string_util.h"

namespace net_instaweb {

/*
common url format

  http://www.foo.bar/z1234/b_c.d?e=f&g=h

this suggests we should have short encodings for  a-zA-Z0-9.:/?&

We would like the above URL to be reasonably legible if possible.
However it's also nice if it's short.

One annoyance is that we are using '.' to delimit the 4 fields of an
instaweb-generated URL.  That can probably be changed to use ^, which
is a legal URL but is rarely used in URLs.  This would enable us to
leave . alone.  But that's probably a moderately painful change
involving a fair amount of regolding.

In the meantime we can replace . with ^ in this encoder so the they
don't change size.  So the transform table is:

a-zA-Z0-9_=+-&? unchanged
%               %%
/               %_
\               %-
http://         %h
.com            %c
.css            %s
.edu            %e
.gif            %g
.html           %t
.jpeg           %k
.jpg            %j
.js             %l
.net            %n
.png            %p
www.            %w
.               ^
^               %^

everything else  %XX  where xx are hex digits using capital latters


The intent of this class to to help encode arbitrary URLs (really, any
stream of 8-byte characters, but optimized for URLs) so that it can be
used in one 'segment' of a new URL.  This means we will not output
. or / but will instead escape those.
*/

class UrlEscaper : public UrlSegmentEncoder {
 public:
  virtual ~UrlEscaper();
  virtual void EncodeToUrlSegment(
      const StringPiece& in, std::string* url_segment);
  virtual bool DecodeFromUrlSegment(
      const StringPiece& url_segment, std::string* out);
};

}  // namespace net_instaweb

#endif  // NET_INSTAWEB_UTIL_PUBLIC_URL_ESCAPER_H_