net/base/sdch_dictionary_fetcher.h

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 // TODO(rdsmith): This class needs to be moved out to the net/ embedder and
   6 // hooked into whatever mechanisms the embedder uses for authentication.
   7 // Specifically, this class needs methods overriding
   8 // URLRequest::Delegate::{OnAuthRequired,OnCertificateRequested} and can't
   9 // implement them at the net/ layer.
  10
  11 #ifndef NET_BASE_SDCH_DICTIONARY_FETCHER_H_
  12 #define NET_BASE_SDCH_DICTIONARY_FETCHER_H_
  13
  14 #include <queue>
  15 #include <set>
  16 #include <string>
  17
  18 #include "base/memory/scoped_ptr.h"
  19 #include "base/memory/weak_ptr.h"
  20 #include "base/threading/non_thread_safe.h"
  21 #include "net/base/sdch_manager.h"
  22 #include "net/url_request/url_fetcher_delegate.h"
  23 #include "net/url_request/url_request.h"
  24
  25 namespace net {
  26
  27 class URLRequest;
  28 class URLRequestThrottlerEntryInterface;
  29
  30 // This class implements the SdchFetcher interface. It queues requests
  31 // for dictionaries and dispatches them serially, implementing
  32 // the URLRequest::Delegate interface to handle callbacks (but see above
  33 // TODO). It tracks all requests, only attempting to fetch each dictionary
  34 // once.
  35 class NET_EXPORT SdchDictionaryFetcher
  36     : public SdchFetcher,
  37       public URLRequest::Delegate,
  38       public base::NonThreadSafe {
  39  public:
  40   // The consumer must guarantee that |*consumer| and |*context| outlive
  41   // this object.
  42   SdchDictionaryFetcher(SdchFetcher::Delegate* consumer,
  43                         URLRequestContext* context);
  44   virtual ~SdchDictionaryFetcher();
  45
  46   // Implementation of SdchFetcher methods.
  47   virtual void Schedule(const GURL& dictionary_url) OVERRIDE;
  48   virtual void Cancel() OVERRIDE;
  49
  50   // Implementation of URLRequest::Delegate methods.
  51   virtual void OnResponseStarted(URLRequest* request) OVERRIDE;
  52   virtual void OnReadCompleted(URLRequest* request, int bytes_read) OVERRIDE;
  53
  54  private:
  55   enum State {
  56     STATE_NONE,
  57     STATE_IDLE,
  58     STATE_REQUEST_STARTED,
  59     STATE_REQUEST_READING,
  60     STATE_REQUEST_COMPLETE,
  61   };
  62
  63   // State machine implementation.
  64   int DoLoop(int rv);
  65   int DoDispatchRequest(int rv);
  66   int DoRequestStarted(int rv);
  67   int DoRead(int rv);
  68   int DoCompleteRequest(int rv);
  69
  70   State next_state_;
  71   bool in_loop_;
  72
  73   SdchFetcher::Delegate* const consumer_;
  74
  75   // A queue of URLs that are being used to download dictionaries.
  76   std::queue<GURL> fetch_queue_;
  77
  78   // The request and buffer used for getting the current dictionary
  79   // Both are null when a fetch is not in progress.
  80   scoped_ptr<URLRequest> current_request_;
  81   scoped_refptr<IOBuffer> buffer_;
  82
  83   // The currently accumulating dictionary.
  84   std::string dictionary_;
  85
  86   // Althought the SDCH spec does not preclude a server from using a single URL
  87   // to load several distinct dictionaries (by telling a client to load a
  88   // dictionary from an URL several times), current implementations seem to have
  89   // that 1-1 relationship (i.e., each URL points at a single dictionary, and
  90   // the dictionary content does not change over time, and hence is not worth
  91   // trying to load more than once). In addition, some dictionaries prove
  92   // unloadable only after downloading them (because they are too large?  ...or
  93   // malformed?). As a protective element, Chromium will *only* load a
  94   // dictionary at most once from a given URL (so that it doesn't waste
  95   // bandwidth trying repeatedly).
  96   // The following set lists all the dictionary URLs that we've tried to load,
  97   // so that we won't try to load from an URL more than once.
  98   // TODO(jar): Try to augment the SDCH proposal to include this restiction.
  99   std::set<GURL> attempted_load_;
 100
 101   // Store the URLRequestContext associated with the owning SdchManager for
 102   // use while fetching.
 103   URLRequestContext* context_;
 104
 105   base::WeakPtrFactory<SdchDictionaryFetcher> weak_factory_;
 106
 107   DISALLOW_COPY_AND_ASSIGN(SdchDictionaryFetcher);
 108 };
 109
 110 }  // namespace net
 111
 112 #endif  // NET_BASE_SDCH_DICTIONARY_FETCHER_H_