Move MimeTypeResourceHandler before ThrottlingResourceHandler

content/browser/loader/mime_sniffing_resource_handler.h

+// Copyright (c) 2012 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.
+
+#ifndef CONTENT_BROWSER_LOADER_MIME_SNIFFING_RESOURCE_HANDLER_H_
+#define CONTENT_BROWSER_LOADER_MIME_SNIFFING_RESOURCE_HANDLER_H_
+
+#include <string>
+#include <vector>
+
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"
+#include "content/browser/loader/layered_resource_handler.h"
+#include "content/common/content_export.h"
+#include "content/public/browser/resource_controller.h"
+
+namespace net {
+class URLRequest;
+}
+
+namespace content {
+class InterceptingResourceHandler;
+class PluginService;
+class ResourceDispatcherHostImpl;
+struct WebPluginInfo;
+
+// ResourceHandler that, if necessary, buffers a response body without passing
+// it to the next ResourceHandler until it can perform mime sniffing on it.
+//
+// Uses the buffer provided by the original event handler for buffering, and
+// continues to reuses it until it can determine the MIME type
+// subsequent reads until it's done buffering.  As a result, the buffer
+// returned by the next ResourceHandler must have a capacity of at least
+// net::kMaxBytesToSniff * 2.
+//
+// Before a request is sent, this ResourceHandler will also set an appropriate
+// Accept header on the request based on its ResourceType, if one isn't already
+// present.
+class CONTENT_EXPORT MimeSniffingResourceHandler
+    : public LayeredResourceHandler,
+      public ResourceController {
+ public:
+  MimeSniffingResourceHandler(std::unique_ptr<ResourceHandler> next_handler,
+                              ResourceDispatcherHostImpl* host,
+                              PluginService* plugin_service,
+                              InterceptingResourceHandler* intercepting_handler,
+                              net::URLRequest* request);
+  ~MimeSniffingResourceHandler() override;
+
+ private:
+  friend class MimeSniffingResourceHandlerTest;
+  enum State {
+    // Starting state of the MimeSniffingResourceHandler. In this state, it is
+    // acting as a blind pass-through ResourceHandler until the response is
+    // received.
+    STATE_STARTING,
+
+    // In this state, the MimeSniffingResourceHandler is buffering the response
+    // data in read_buffer_, waiting to sniff the mime type and make a choice
+    // about request interception.
+    STATE_BUFFERING,
+
+    // In this state, the MimeSniffingResourceHandler has identified the mime
+    // type and made a decision on whether the request should be intercepted or
+    // not. It is nows attempting to replay the response to downstream
+    // handlers.
+    STATE_INTERCEPTION_CHECK_DONE,
+
+    // In this state, the MimeSniffingResourceHandler is replaying the buffered
+    // OnResponseStarted event to the downstream ResourceHandlers.
+    STATE_REPLAYING_RESPONSE_RECEIVED,
+
+    // In this state, the MimeSniffingResourceHandler is just a blind
+    // pass-through
+    // ResourceHandler.
+    STATE_STREAMING,
+  };
+
+  // ResourceHandler implementation:
+  void SetController(ResourceController* controller) override;
+  bool OnWillStart(const GURL&, bool* defer) override;
+  bool OnResponseStarted(ResourceResponse* response, bool* defer) override;
+  bool OnWillRead(scoped_refptr<net::IOBuffer>* buf,
+                  int* buf_size,
+                  int min_size) override;
+  bool OnReadCompleted(int bytes_read, bool* defer) override;
+  void OnResponseCompleted(const net::URLRequestStatus& status,
+                           const std::string& security_info,
+                           bool* defer) override;
+
+  // ResourceController implementation:
+  void Resume() override;
+  void Cancel() override;
+  void CancelAndIgnore() override;
+  void CancelWithError(int error_code) override;
+
+  // --------------------------------------------------------------------------
+  // The following methods replay the buffered data to the downstream
+  // ResourceHandlers. They return false if the request should be cancelled,
+  // true otherwise. Each of them will set |defer| to true if the request will
+  // proceed to the next stage asynchronously.
+
+  // Used to advance through the states of the state machine.
+  void AdvanceState();
+  bool ProcessState(bool* defer);
+
+  // Intercepts the request as a stream/download if needed.
+  bool MaybeIntercept(bool* defer);
+
+  // Replays OnResponseStarted on the downstream handlers.
+  bool ReplayResponseReceived(bool* defer);
+
+  // Replays OnReadCompleted on the downstreams handlers.
+  bool ReplayReadCompleted(bool* defer);
+
+  // --------------------------------------------------------------------------
+
+  // Whether the response body should be sniffed in order to determine the MIME
+  // type of the response.
+  bool ShouldSniffContent();
+
+  // Checks whether this request should be intercepted as a stream or a
+  // download. If this is the case, sets up the new ResourceHandler that will be
+  // used for interception. Returns false if teh request should be cancelled,
+  // true otherwise. |defer| is set to true if the interception check needs to
+  // finish asynchronously.
+  bool MaybeStartInterception(bool* defer);
+
+  // Determines whether a plugin will handle the current request. Returns false
+  // if there is an error and the request should be cancelled and true
+  // otherwise. |defer| is set to true if plugin data is stale and needs to be
+  // refreshed before the request can be handled (in this case the function
+  // still returns true). If the request is directed to a plugin,
+  // |handled_by_plugin| is set to true.
+  bool CheckForPluginHandler(bool* defer, bool* handled_by_plugin);
+
+  // Whether this request is allowed to be intercepted as a download or a
+  // stream.
+  bool CanBeIntercepted();
+
+  // Whether the response we received is not provisional.
+  bool CheckResponseIsNotProvisional();
+
+  bool MustDownload();
+
+  // Called on the IO thread once the list of plugins has been loaded.
+  void OnPluginsLoaded(const std::vector<WebPluginInfo>& plugins);
+
+  State state_;
+
+  ResourceDispatcherHostImpl* host_;
+#if defined(ENABLE_PLUGINS)
+  PluginService* plugin_service_;
+#endif
+
+  bool must_download_;
+  bool must_download_is_set_;
+
+  // Used to buffer the reponse received until replay.
+  scoped_refptr<ResourceResponse> response_;
+  scoped_refptr<net::IOBuffer> read_buffer_;
+  int read_buffer_size_;
+  int bytes_read_;
+
+  // The InterceptingResourceHandler that will perform ResourceHandler swap if
+  // needed.
+  InterceptingResourceHandler* intercepting_handler_;
+
+  base::WeakPtrFactory<MimeSniffingResourceHandler> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(MimeSniffingResourceHandler);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_LOADER_MIME_SNIFFING_RESOURCE_HANDLER_H_