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+// Copyright (c) 2006-2008 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.
+
+// Provides global database of differential decompression dictionaries for the
+// SDCH filter (processes sdch enconded content).
+
+// Exactly one instance of SdchManager is built, and all references are made
+// into that collection.
+//
+// The SdchManager maintains a collection of memory resident dictionaries.  It
+// can find a dictionary (based on a server specification of a hash), store a
+// dictionary, and make judgements about what URLs can use, set, etc. a
+// dictionary.
+
+// These dictionaries are acquired over the net, and include a header
+// (containing metadata) as well as a VCDIFF dictionary (for use by a VCDIFF
+// module) to decompress data.
+
+#ifndef NET_BASE_SDCH_MANAGER_H_
+#define NET_BASE_SDCH_MANAGER_H_
+
+#include <map>
+#include <set>
+#include <string>
+
+#include "base/ref_counted.h"
+#include "base/time.h"
+#include "googleurl/src/gurl.h"
+
+
+//------------------------------------------------------------------------------
+// Create a public interface to help us load SDCH dictionaries.  
+// The SdchManager class allows registration to support this interface.
+// A browser may register a fetcher that is used by the dictionary managers to
+// get data from a specified URL.  This allows us to use very high level browser
+// functionality in this base (when the functionaity can be provided).
+class SdchFetcher {
+ public:
+  SdchFetcher() {}
+  virtual ~SdchFetcher() {}
+
+  // The Schedule() method is called when there is a need to get a dictionary
+  // from a server.  The callee is responsible for getting that dictionary_text,
+  // and then calling back to AddSdchDictionary() to the SdchManager instance.
+  virtual void Schedule(const GURL& dictionary_url) = 0;
+ private:
+  DISALLOW_COPY_AND_ASSIGN(SdchFetcher);
+};
+//------------------------------------------------------------------------------
+
+class SdchManager {
+ public:
+  // There is one instance of |Dictionary| for each memory-cached SDCH
+  // dictionary.
+  class Dictionary : public base::RefCounted<Dictionary> {
+   public:
+    // Sdch filters can get our text to use in decoding compressed data.
+    const std::string& text() const { return text_; }
+
+   private:
+    friend class SdchManager;  // Only manager can construct an instance.
+
+    // Construct a vc-diff usable dictionary from the dictionary_text starting
+    // at the given offset.  The supplied client_hash should be used to
+    // advertise the dictionary's availability relative to the suppplied URL.
+    Dictionary(const std::string& dictionary_text, size_t offset,
+               const std::string& client_hash, const GURL& url,
+               const std::string& domain, const std::string& path,
+               const Time& expiration, const std::set<int> ports);
+
+    const GURL& url() const { return url_; }
+    const std::string& client_hash() const { return client_hash_; }
+
+    // For a given URL, get the actual or default port.
+    static int GetPortIncludingDefault(const GURL& url);
+
+    // Security method to check if we can advertise this dictionary for use
+    // if the |target_url| returns SDCH compressed data.
+    bool CanAdvertise(const GURL& target_url);
+
+    // Security methods to check if we can establish a new dictionary with the
+    // given data, that arrived in response to get of dictionary_url.
+    static bool CanSet(const std::string& domain, const std::string& path,
+                       const std::set<int> ports, const GURL& dictionary_url);
+
+    // Security method to check if we can use a dictionary to decompress a
+    // target that arrived with a reference to this dictionary.
+    bool CanUse(const GURL referring_url);
+
+    // Compare paths to see if they "match" for dictionary use.
+    static bool PathMatch(const std::string& path,
+                          const std::string& restriction);
+
+    // Compare domains to see if the "match" for dictionary use.
+    static bool DomainMatch(const GURL& url, const std::string& restriction);
+
+    // Each dictionary payload consists of several headers, followed by the text
+    // of the dictionary.  The following are the known headers.
+    std::string domain_attribute_;
+    std::set<int> ports_;
+
+    // The actual text of the dictionary.
+    std::string text_;
+
+    // Part of the hash of text_ that the client uses to advertise the fact that
+    // it has a specific dictionary pre-cached.
+    std::string client_hash_;
+
+    // The GURL that arrived with the text_ in a URL request to specify where
+    // this dictionary may be used.
+    const GURL url_;
+
+    // Metadate "headers" in before dictionary text contained the following:
+    const std::string domain_;
+    const std::string path_;
+    const Time expiration_;  // Implied by max-age.
+    const std::set<int> ports;
+
+    DISALLOW_COPY_AND_ASSIGN(Dictionary);
+  };
+
+  SdchManager();
+  ~SdchManager();
+
+  // Provide access to the single instance of this class.
+  static SdchManager* Global();
+
+  // Register a fetcher that this class can use to obtain dictionaries.
+  void set_sdch_fetcher(SdchFetcher* fetcher) { fetcher_.reset(fetcher); }
+
+  // If called with an empty string, advertise and support sdch on all domains.
+  // If called with a specific string, advertise and support only the specified
+  // domain.
+  static void enable_sdch_support(const std::string& domain) {
+    // We presume that there is a SDCH manager instance.
+    global_->supported_domain_ = domain;
+    global_->sdch_enabled_ = true;
+  }
+  
+  const bool IsInSupportedDomain(const GURL& url) const;
+
+  // Schedule the URL fetching to load a dictionary. This will generally return
+  // long before the dictionary is actually loaded and added.
+  // After the implied task does completes, the dictionary will have been
+  // cached in memory.
+  void FetchDictionary(const GURL& referring_url, const GURL& dictionary_url);
+
+  // Add an SDCH dictionary to our list of availible dictionaries. This addition
+  // will fail (return false) if addition is illegal (data in the dictionary is
+  // not acceptable from the dictionary_url; dictionary already added, etc.).
+  bool AddSdchDictionary(const std::string& dictionary_text,
+                         const GURL& dictionary_url);
+
+  // Find the vcdiff dictionary (the body of the sdch dictionary that appears
+  // after the meta-data headers like Domain:...) with the given |server_hash|
+  // to use to decompreses data that arrived as SDCH encoded content.  Check to
+  // be sure the returned |dictionary| can be used for decoding content supplied
+  // in response to a request for |referring_url|.
+  // Caller is responsible for AddRef()ing the dictionary, and Release()ing it
+  // when done.
+  // Return null in |dictionary| if there is no matching legal dictionary.
+  void GetVcdiffDictionary(const std::string& server_hash, const GURL& referring_url,
+                           Dictionary** dictionary);
+
+  // Get list of available (pre-cached) dictionaries that we have already loaded
+  // into memory.  The list is a comma separated list of (client) hashes per
+  // the SDCH spec.
+  void GetAvailDictionaryList(const GURL& target_url, std::string* list);
+
+  // Construct the pair of hashes for client and server to identify an SDCH
+  // dictionary.  This is only made public to facilitate unit testing, but is
+  // otherwise private
+  static void GenerateHash(const std::string& dictionary_text,
+                           std::string* client_hash, std::string* server_hash);
+
+ private:
+  // A map of dictionaries info indexed by the hash that the server provides.
+  typedef std::map<std::string, Dictionary*> DictionaryMap;
+
+  // The one global instance of that holds all the data.
+  static SdchManager* global_;
+
+  // A simple implementatino of a RFC 3548 "URL safe" base64 encoder.
+  static void UrlSafeBase64Encode(const std::string& input,
+                                  std::string* output);
+  DictionaryMap dictionaries_;
+
+  // An instance that can fetch a dictionary given a URL.
+  scoped_ptr<SdchFetcher> fetcher_;
+
+  // Support SDCH compression, by advertising in headers.
+  bool sdch_enabled_;
+
+  // Empty string means all domains.  Non-empty means support only the given
+  // domain is supported.
+  std::string supported_domain_;
+
+  DISALLOW_COPY_AND_ASSIGN(SdchManager);
+};
+
+#endif  // NET_BASE_SDCH_MANAGER_H_