net/url_request/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 delegate URLRequest::Delegate methods
   6 // to the net/ embedder for correct implementation of authentication.
   7 // Specifically, this class needs the embedder to provide functionality
   8 // corresponding to
   9 // URLRequest::Delegate::{OnAuthRequired,OnCertificateRequested}.
  10
  11 #ifndef NET_URL_REQUEST_SDCH_DICTIONARY_FETCHER_H_
  12 #define NET_URL_REQUEST_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 is used by embedder SDCH policy object to fetch
  31 // dictionaries. It queues requests for dictionaries and dispatches
  32 // them serially, implementing the URLRequest::Delegate interface to
  33 // handle callbacks (but see above TODO). It tracks all requests, only
  34 // attempting to fetch each dictionary once.
  35 class NET_EXPORT SdchDictionaryFetcher : public URLRequest::Delegate,
  36                                          public base::NonThreadSafe {
  37  public:
  38   typedef base::Callback<void(const std::string& dictionary_text,
  39                               const GURL& dictionary_url,
  40                               const BoundNetLog& net_log)>
  41       OnDictionaryFetchedCallback;
  42
  43   // The consumer must guarantee that |*context| outlives this object.
  44   // |callback| will be called on successful dictionary fetch
  45   // requested through Schedule().  |callback| will not be called
  46   // after object destruction.
  47   SdchDictionaryFetcher(URLRequestContext* context,
  48                         const OnDictionaryFetchedCallback& callback);
  49   ~SdchDictionaryFetcher() override;
  50
  51   // Request a new dictionary fetch.
  52   void Schedule(const GURL& dictionary_url);
  53
  54   // Cancel any in-progress requests.
  55   void Cancel();
  56
  57   // Implementation of URLRequest::Delegate methods.
  58   void OnResponseStarted(URLRequest* request) override;
  59   void OnReadCompleted(URLRequest* request, int bytes_read) override;
  60
  61  private:
  62   enum State {
  63     STATE_NONE,
  64     STATE_IDLE,
  65     STATE_REQUEST_STARTED,
  66     STATE_REQUEST_READING,
  67     STATE_REQUEST_COMPLETE,
  68   };
  69
  70   // State machine implementation.
  71   int DoLoop(int rv);
  72   int DoDispatchRequest(int rv);
  73   int DoRequestStarted(int rv);
  74   int DoRead(int rv);
  75   int DoCompleteRequest(int rv);
  76
  77   State next_state_;
  78   bool in_loop_;
  79
  80   // A queue of URLs that are being used to download dictionaries.
  81   std::queue<GURL> fetch_queue_;
  82
  83   // The request and buffer used for getting the current dictionary
  84   // Both are null when a fetch is not in progress.
  85   scoped_ptr<URLRequest> current_request_;
  86   scoped_refptr<IOBuffer> buffer_;
  87
  88   // The currently accumulating dictionary.
  89   std::string dictionary_;
  90
  91   // Althought the SDCH spec does not preclude a server from using a single URL
  92   // to load several distinct dictionaries (by telling a client to load a
  93   // dictionary from an URL several times), current implementations seem to have
  94   // that 1-1 relationship (i.e., each URL points at a single dictionary, and
  95   // the dictionary content does not change over time, and hence is not worth
  96   // trying to load more than once). In addition, some dictionaries prove
  97   // unloadable only after downloading them (because they are too large?  ...or
  98   // malformed?). As a protective element, Chromium will *only* load a
  99   // dictionary at most once from a given URL (so that it doesn't waste
 100   // bandwidth trying repeatedly).
 101   // The following set lists all the dictionary URLs that we've tried to load,
 102   // so that we won't try to load from an URL more than once.
 103   // TODO(jar): Try to augment the SDCH proposal to include this restiction.
 104   std::set<GURL> attempted_load_;
 105
 106   // Store the URLRequestContext associated with the owning SdchManager for
 107   // use while fetching.
 108   URLRequestContext* const context_;
 109
 110   const OnDictionaryFetchedCallback dictionary_fetched_callback_;
 111
 112   base::WeakPtrFactory<SdchDictionaryFetcher> weak_factory_;
 113
 114   DISALLOW_COPY_AND_ASSIGN(SdchDictionaryFetcher);
 115 };
 116
 117 }  // namespace net
 118
 119 #endif  // NET_URL_REQUEST_SDCH_DICTIONARY_FETCHER_H_