// Copyright (c) 2010 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// URL filename encoder goals:
//
// 1. Allow URLs with arbitrary path-segment length, generating filenames
// with a maximum of 128 characters.
// 2. Provide a somewhat human readable filenames, for easy debugging flow.
// 3. Provide reverse-mapping from filenames back to URLs.
// 4. Be able to distinguish http://x from http://x/ from http://x/index.html.
// Those can all be different URLs.
// 5. Be able to represent http://a/b/c and http://a/b/c/d, a pattern seen
// with Facebook Connect.
//
// We need an escape-character for representing characters that are legal
// in URL paths, but not in filenames, such as '?'.
//
// We can pick any legal character as an escape, as long as we escape it too.
// But as we have a goal of having filenames that humans can correlate with
// URLs, we should pick one that doesn't show up frequently in URLs. Candidates
// are ~`!@#$%^&()-=_+{}[],. but we would prefer to avoid characters that are
// shell escapes or that various build tools use.
//
// .#&%-=_+ occur frequently in URLs.
// <>:"/\|?* are illegal in Windows
// See http://msdn.microsoft.com/en-us/library/aa365247(VS.85).aspx
// ~`!$^&(){}[]'; are special to Unix shells
// In addition, build tools do not like ^@#%
//
// Josh took a quick look at the frequency of some special characters in
// Sadeesh's slurped directory from Fall 09 and found the following occurances:
//
// ^ 3 build tool doesn't like ^ in testdata filenames
// @ 10 build tool doesn't like @ in testdata filenames
// . 1676 too frequent in URLs
// , 76 THE WINNER
// # 0 build tool doesn't like it
// & 487 Prefer to avoid shell escapes
// % 374 g4 doesn't like it
// = 579 very frequent in URLs -- leave unmodified
// - 464 very frequent in URLs -- leave unmodified
// _ 798 very frequent in URLs -- leave unmodified
//
//
// The escaping algorithm is:
// 1) Escape all unfriendly symbols as ,XX where XX is the hex code.
// 2) Add a ',' at the end (We do not allow ',' at end of any directory name,
// so this assures that e.g. /a and /a/b can coexist in the filesystem).
// 3) Go through the path segment by segment (where a segment is one directory
// or leaf in the path) and
// 3a) If the segment is empty, escape the second slash. i.e. if it was
// www.foo.com//a then we escape the second / like www.foo.com/,2Fa,
// 3a) If it is "." or ".." prepend with ',' (so that we have a non-
// empty and non-reserved filename).
// 3b) If it is over 128 characters, break it up into smaller segments by
// inserting ,-/ (Windows limits paths to 128 chars, other OSes also
// have limits that would restrict us)
//
// For example:
// URL File
// / /,
// /index.html /index.html,
// /. /.,
// /a/b /a/b,
// /a/b/ /a/b/,
// /a/b/c /a/b/c, Note: no prefix problem
// /u?foo=bar /u,3Ffoo=bar,
// // /,2F,
// /./ /,./,
// /../ /,../,
// /, /,2C,
// /,./ /,2C./,
// /very...longname/ /very...long,-/name If very...long is about 126 long.
// NOTE: we avoid using some classes here (like FilePath and GURL) because we
// share this code with other projects externally.
#ifndef NET_TOOLS_DUMP_CACHE_URL_TO_FILENAME_ENCODER_H_
#define NET_TOOLS_DUMP_CACHE_URL_TO_FILENAME_ENCODER_H_
#include <string>
#include "base/strings/string_util.h"
#include "net/tools/dump_cache/url_utilities.h"
namespace net {
// Helper class for converting a URL into a filename.
class UrlToFilenameEncoder {
public:
// Given a |url| and a |base_path|, returns a filename which represents this
// |url|. |url| may include URL escaping such as %21 for !
// |legacy_escape| indicates that this function should use the old-style
// of encoding.
// TODO(mbelshe): delete the legacy_escape code.
static std::string Encode(const std::string& url, std::string base_path,
bool legacy_escape) {
std::string filename;
if (!legacy_escape) {
std::string url_no_scheme = UrlUtilities::GetUrlHostPath(url);
EncodeSegment(base_path, url_no_scheme, '/', &filename);
#ifdef WIN32
ReplaceAll(&filename, "/", "\\");
#endif
} else {
std::string clean_url(url);
if (clean_url.length() && clean_url[clean_url.length()-1] == '/')
clean_url.append("index.html");
std::string host = UrlUtilities::GetUrlHost(clean_url);
filename.append(base_path);
filename.append(host);
#ifdef WIN32
filename.append("\\");
#else
filename.append("/");
#endif
std::string url_filename = UrlUtilities::GetUrlPath(clean_url);
// Strip the leading '/'.
if (url_filename[0] == '/')
url_filename = url_filename.substr(1);
// Replace '/' with '\'.
ConvertToSlashes(&url_filename);
// Strip double back-slashes ("\\\\").
StripDoubleSlashes(&url_filename);
// Save path as filesystem-safe characters.
url_filename = LegacyEscape(url_filename);
filename.append(url_filename);
#ifndef WIN32
// Last step - convert to native slashes.
const std::string slash("/");
const std::string backslash("\\");
ReplaceAll(&filename, backslash, slash);
#endif
}
return filename;
}
// Rewrite HTML in a form that the SPDY in-memory server
// can read.
// |filename_prefix| is prepended without escaping.
// |escaped_ending| is the URL to be encoded into a filename. It may have URL
// escaped characters (like %21 for !).
// |dir_separator| is "/" on Unix, "\" on Windows.
// |encoded_filename| is the resultant filename.
static void EncodeSegment(
const std::string& filename_prefix,
const std::string& escaped_ending,
char dir_separator,
std::string* encoded_filename);
// Decodes a filename that was encoded with EncodeSegment,
// yielding back the original URL.
static bool Decode(const std::string& encoded_filename,
char dir_separator,
std::string* decoded_url);
static const char kEscapeChar;
static const char kTruncationChar;
static const size_t kMaximumSubdirectoryLength;
friend class UrlToFilenameEncoderTest;
private:
// Appends a segment of the path, special-casing "." and "..", and
// ensuring that the segment does not exceed the path length. If it does,
// it chops the end off the segment, writes the segment with a separator of
// ",-/", and then rewrites segment to contain just the truncated piece so
// it can be used in the next iteration.
// |segment| is a read/write parameter containing segment to write
// Note: this should not be called with empty segment.
static void AppendSegment(std::string* segment, std::string* dest);
// Allow reading of old slurped files.
static std::string LegacyEscape(const std::string& path);
// Replace all instances of |from| within |str| as |to|.
static void ReplaceAll(std::string* str, const std::string& from,
const std::string& to) {
std::string::size_type pos(0);
while ((pos = str->find(from, pos)) != std::string::npos) {
str->replace(pos, from.size(), to);
pos += from.size();
}
}
// Replace all instances of "/" with "\" in |path|.
static void ConvertToSlashes(std::string* path) {
const std::string slash("/");
const std::string backslash("\\");
ReplaceAll(path, slash, backslash);
}
// Replace all instances of "\\" with "%5C%5C" in |path|.
static void StripDoubleSlashes(std::string* path) {
const std::string doubleslash("\\\\");
const std::string escaped_doubleslash("%5C%5C");
ReplaceAll(path, doubleslash, escaped_doubleslash);
}
};
} // namespace net
#endif // NET_TOOLS_DUMP_CACHE_URL_TO_FILENAME_ENCODER_H_