Restructure SDCH layering to allow more separation (observer/1->[0,n]

net/base/sdch_dictionary_fetcher.h

-// Copyright 2014 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.
-
-// TODO(rdsmith): This class needs to be moved out to the net/ embedder and
-// hooked into whatever mechanisms the embedder uses for authentication.
-// Specifically, this class needs methods overriding
-// URLRequest::Delegate::{OnAuthRequired,OnCertificateRequested} and can't
-// implement them at the net/ layer.
-
-#ifndef NET_BASE_SDCH_DICTIONARY_FETCHER_H_
-#define NET_BASE_SDCH_DICTIONARY_FETCHER_H_
-
-#include <queue>
-#include <set>
-#include <string>
-
-#include "base/memory/scoped_ptr.h"
-#include "base/memory/weak_ptr.h"
-#include "base/threading/non_thread_safe.h"
-#include "net/base/sdch_manager.h"
-#include "net/url_request/url_fetcher_delegate.h"
-#include "net/url_request/url_request.h"
-
-namespace net {
-
-class URLRequest;
-class URLRequestThrottlerEntryInterface;
-
-// This class implements the SdchFetcher interface. It queues requests
-// for dictionaries and dispatches them serially, implementing
-// the URLRequest::Delegate interface to handle callbacks (but see above
-// TODO). It tracks all requests, only attempting to fetch each dictionary
-// once.
-class NET_EXPORT SdchDictionaryFetcher
-    : public SdchFetcher,
-      public URLRequest::Delegate,
-      public base::NonThreadSafe {
- public:
-  // The consumer must guarantee that |*consumer| and |*context| outlive
-  // this object.
-  SdchDictionaryFetcher(SdchFetcher::Delegate* consumer,
-                        URLRequestContext* context);
-  virtual ~SdchDictionaryFetcher();
-
-  // Implementation of SdchFetcher methods.
-  virtual void Schedule(const GURL& dictionary_url) OVERRIDE;
-  virtual void Cancel() OVERRIDE;
-
-  // Implementation of URLRequest::Delegate methods.
-  virtual void OnResponseStarted(URLRequest* request) OVERRIDE;
-  virtual void OnReadCompleted(URLRequest* request, int bytes_read) OVERRIDE;
-
- private:
-  enum State {
-    STATE_NONE,
-    STATE_IDLE,
-    STATE_REQUEST_STARTED,
-    STATE_REQUEST_READING,
-    STATE_REQUEST_COMPLETE,
-  };
-
-  // State machine implementation.
-  int DoLoop(int rv);
-  int DoDispatchRequest(int rv);
-  int DoRequestStarted(int rv);
-  int DoRead(int rv);
-  int DoCompleteRequest(int rv);
-
-  State next_state_;
-  bool in_loop_;
-
-  SdchFetcher::Delegate* const consumer_;
-
-  // A queue of URLs that are being used to download dictionaries.
-  std::queue<GURL> fetch_queue_;
-
-  // The request and buffer used for getting the current dictionary
-  // Both are null when a fetch is not in progress.
-  scoped_ptr<URLRequest> current_request_;
-  scoped_refptr<IOBuffer> buffer_;
-
-  // The currently accumulating dictionary.
-  std::string dictionary_;
-
-  // Althought the SDCH spec does not preclude a server from using a single URL
-  // to load several distinct dictionaries (by telling a client to load a
-  // dictionary from an URL several times), current implementations seem to have
-  // that 1-1 relationship (i.e., each URL points at a single dictionary, and
-  // the dictionary content does not change over time, and hence is not worth
-  // trying to load more than once). In addition, some dictionaries prove
-  // unloadable only after downloading them (because they are too large?  ...or
-  // malformed?). As a protective element, Chromium will *only* load a
-  // dictionary at most once from a given URL (so that it doesn't waste
-  // bandwidth trying repeatedly).
-  // The following set lists all the dictionary URLs that we've tried to load,
-  // so that we won't try to load from an URL more than once.
-  // TODO(jar): Try to augment the SDCH proposal to include this restiction.
-  std::set<GURL> attempted_load_;
-
-  // Store the URLRequestContext associated with the owning SdchManager for
-  // use while fetching.
-  URLRequestContext* context_;
-
-  base::WeakPtrFactory<SdchDictionaryFetcher> weak_factory_;
-
-  DISALLOW_COPY_AND_ASSIGN(SdchDictionaryFetcher);
-};
-
-}  // namespace net
-
-#endif  // NET_BASE_SDCH_DICTIONARY_FETCHER_H_