[ON HOLD] Implement pull-based design for content decoding

net/url_request/url_request_job.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 NET_URL_REQUEST_URL_REQUEST_JOB_H_
 #define NET_URL_REQUEST_URL_REQUEST_JOB_H_
 
 #include <stdint.h>
 
 #include <memory>
 #include <string>
 #include <vector>
 
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "base/message_loop/message_loop.h"
 #include "base/power_monitor/power_observer.h"
 #include "net/base/host_port_pair.h"
 #include "net/base/load_states.h"
 #include "net/base/net_error_details.h"
 #include "net/base/net_export.h"
 #include "net/base/request_priority.h"
 #include "net/base/upload_progress.h"
 #include "net/cookies/canonical_cookie.h"
+#include "net/filter/stream_source.h"
 #include "net/socket/connection_attempts.h"
 #include "net/url_request/redirect_info.h"
 #include "net/url_request/url_request.h"
 #include "url/gurl.h"
 
 namespace net {
 
 class AuthChallengeInfo;
 class AuthCredentials;
 class CookieOptions;
 class Filter;
 class HttpRequestHeaders;
 class HttpResponseInfo;
 class IOBuffer;
 struct LoadTimingInfo;
 class NetworkDelegate;
 class SSLCertRequestInfo;
 class SSLInfo;
 class SSLPrivateKey;
 class UploadDataStream;
 class URLRequestStatus;
 class X509Certificate;
 
 class NET_EXPORT URLRequestJob : public base::PowerObserver {
  public:
+  typedef base::Callback<void(net::Error, size_t)> ReadRawCompleteCallback;
   explicit URLRequestJob(URLRequest* request,
                          NetworkDelegate* network_delegate);
   ~URLRequestJob() override;
 
   // Returns the request that owns this job.
   URLRequest* request() const {
     return request_;
   }
 
   // Sets the upload data, most requests have no upload data, so this is a NOP.
@@ skipping 82 matching lines @@
   // Returns the cookie values included in the response, if applicable.
   // Returns true if applicable.
   // NOTE: This removes the cookies from the job, so it will only return
   //       useful results once per job.
   virtual bool GetResponseCookies(std::vector<std::string>* cookies);
 
   // Populates the network error details of the most recent origin that the
   // network stack makes the request to.
   virtual void PopulateNetErrorDetails(NetErrorDetails* details) const;
 
-  // Called to setup a stream filter for this request. An example of filter is
-  // content encoding/decoding.
-  // Subclasses should return the appropriate Filter, or NULL for no Filter.
-  // This class takes ownership of the returned Filter.
-  //
-  // The default implementation returns NULL.
-  virtual Filter* SetupFilter() const;
+  // Called to set up a StreamSource chain for this request.
+  // Subclasses should return the appropriate first StreamSource of the chain,
+  // or nullptr if no StreamSource should be used. This class takes ownership of
+  // the returned StreamSource.
+  virtual std::unique_ptr<StreamSource> SetupSource();
 
   // Called to determine if this response is a redirect.  Only makes sense
   // for some types of requests.  This method returns true if the response
   // is a redirect, and fills in the location param with the URL of the
   // redirect.  The HTTP status code (e.g., 302) is filled into
   // |*http_status_code| to signify the type of redirect.
   //
   // The caller is responsible for following the redirect by setting up an
   // appropriate replacement Job. Note that the redirected location may be
   // invalid, the caller should be sure it can handle this.
@@ skipping 76 matching lines @@
   // has failed or the response headers have been received.
   virtual void GetConnectionAttempts(ConnectionAttempts* out) const;
 
   // Given |policy|, |referrer|, and |redirect_destination|, returns the
   // referrer URL mandated by |request|'s referrer policy.
   static GURL ComputeReferrerForRedirect(URLRequest::ReferrerPolicy policy,
                                          const std::string& referrer,
                                          const GURL& redirect_destination);
 
  protected:
+  // Callback for asynchronous reads from |source_|. See the documentation for
+  // |Read| above for the contract of this method.
+  void SourceReadComplete(Error error, size_t bytes_read);
+
   // Notifies the job that a certificate is requested.
   void NotifyCertificateRequested(SSLCertRequestInfo* cert_request_info);
 
   // Notifies the job about an SSL certificate error.
   void NotifySSLCertificateError(const SSLInfo& ssl_info, bool fatal);
 
   // Delegates to URLRequest::Delegate.
   bool CanGetCookies(const CookieList& cookie_list) const;
 
   // Delegates to URLRequest::Delegate.
@@ skipping 40 matching lines @@
 
   // Called to tell the job that a filter has successfully reached the end of
   // the stream.
   virtual void DoneReading();
 
   // Called to tell the job that the body won't be read because it's a redirect.
   // This is needed so that redirect headers can be cached even though their
   // bodies are never read.
   virtual void DoneReadingRedirectResponse();
 
-  // Reads filtered data from the request. Returns OK if immediately successful,
-  // ERR_IO_PENDING if the request couldn't complete synchronously, and some
-  // other error code if the request failed synchronously. Note that this
-  // function can issue new asynchronous requests if needed, in which case it
-  // returns ERR_IO_PENDING. If this method completes synchronously,
-  // |*bytes_read| is the number of bytes output by the filter chain if this
-  // method returns OK, or zero if this method returns an error.
-  Error ReadFilteredData(int* bytes_read);
-
-  // Whether the response is being filtered in this job.
-  // Only valid after NotifyHeadersComplete() has been called.
-  bool HasFilter() { return filter_ != NULL; }
-
-  // At or near destruction time, a derived class may request that the filters
-  // be destroyed so that statistics can be gathered while the derived class is
-  // still present to assist in calculations.  This is used by URLRequestHttpJob
-  // to get SDCH to emit stats.
-  void DestroyFilters();
-
   // Provides derived classes with access to the request's network delegate.
   NetworkDelegate* network_delegate() { return network_delegate_; }
 
   // The status of the job.
   const URLRequestStatus GetStatus();
 
   // Set the proxy server that was used, if any.
   void SetProxyServer(const HostPortPair& proxy_server);
 
   // The number of bytes read before passing to the filter. This value reflects
   // bytes read even when there is no filter.
-  int64_t prefilter_bytes_read() const { return prefilter_bytes_read_; }
+  int64_t prefilter_bytes_read() const;
 
   // The number of bytes read after passing through the filter. This value
   // reflects bytes read even when there is no filter.
-  int64_t postfilter_bytes_read() const { return postfilter_bytes_read_; }
+  int64_t postfilter_bytes_read() const;
 
   // Turns an integer result code into an Error and a count of bytes read.
   // The semantics are:
   //   |result| >= 0: |*error| == OK, |*count| == |result|
   //   |result| < 0: |*error| = |result|, |*count| == 0
   static void ConvertResultToError(int result, Error* error, int* count);
 
   // Completion callback for raw reads. See |ReadRawData| for details.
   // |bytes_read| is either >= 0 to indicate a successful read and count of
   // bytes read, or < 0 to indicate an error.
   void ReadRawDataComplete(int bytes_read);
 
   // The request that initiated this job. This value will never be nullptr.
   URLRequest* request_;
 
  private:
+  class URLRequestJobStreamSource;

[Randy Smith (Not in Mondays), 2016/04/26 21:54:02]

I don't see this class referred to in the header file; is there any need to
declare it here?

[xunjieli, 2016/07/20 21:00:48]

The declaration here is needed because this class needs to access the private
method (ReadRawDataHelper) of the enclosing class. 

   // Set the status of the associated URLRequest.
   // TODO(mmenke): Make the URLRequest manage its own status.
   void SetStatus(const URLRequestStatus& status);
 
-  // When data filtering is enabled, this function is used to read data
-  // for the filter. Returns a net error code to indicate if raw data was
-  // successfully read,  an error happened, or the IO is pending.
-  Error ReadRawDataForFilter(int* bytes_read);
-
-  // Informs the filter chain that data has been read into its buffer.
-  void PushInputToFilter(int bytes_read);
-
   // Invokes ReadRawData and records bytes read if the read completes
   // synchronously.
-  Error ReadRawDataHelper(IOBuffer* buf, int buf_size, int* bytes_read);
+  Error ReadRawDataHelper(IOBuffer* buf,
+                          int buf_size,
+                          int* bytes_read,
+                          const StreamSource::OnReadCompleteCallback& callback);
 
   // Called in response to a redirect that was not canceled to follow the
   // redirect. The current job will be replaced with a new job loading the
   // given redirect destination.
   void FollowRedirect(const RedirectInfo& redirect_info);
 
   // Called after every raw read. If |bytes_read| is > 0, this indicates
   // a successful read of |bytes_read| unfiltered bytes. If |bytes_read|
   // is 0, this indicates that there is no additional data to read. |error|
   // specifies whether an error occurred and no bytes were read.
   void GatherRawReadStats(Error error, int bytes_read);
 
   // Updates the profiling info and notifies observers that an additional
   // |bytes_read| unfiltered bytes have been read for this job.
   void RecordBytesRead(int bytes_read);
 
-  // Called to query whether there is data available in the filter to be read
-  // out.
-  bool FilterHasData();
-
   // NotifyDone marks that request is done. It is really a glorified
   // set_status, but also does internal state checking and job tracking. It
   // should be called once per request, when the job is finished doing all IO.
   void NotifyDone(const URLRequestStatus& status);
 
   // Some work performed by NotifyDone must be completed asynchronously so
   // as to avoid re-entering URLRequest::Delegate. This method performs that
   // work.
   void CompleteNotifyDone();
 
   // Subclasses may implement this method to record packet arrival times.
   // The default implementation does nothing.  Only invoked when bytes have been
   // read since the last invocation.
   virtual void UpdatePacketReadTimes();
 
   // Computes a new RedirectInfo based on receiving a redirect response of
   // |location| and |http_status_code|.
   RedirectInfo ComputeRedirectInfo(const GURL& location, int http_status_code);
 
   // Notify the network delegate that more bytes have been received or sent over
   // the network, if bytes have been received or sent since the previous
   // notification.
   void MaybeNotifyNetworkBytes();
 
   // Indicates that the job is done producing data, either it has completed
   // all the data or an error has been encountered. Set exclusively by
   // NotifyDone so that it is kept in sync with the request.
   bool done_;
 
-  int64_t prefilter_bytes_read_;
-  int64_t postfilter_bytes_read_;
-
-  // The data stream filter which is enabled on demand.
-  std::unique_ptr<Filter> filter_;
+  // The first StreamSource of the StreamSource chain used.
+  std::unique_ptr<StreamSource> source_;
 
   // If the filter filled its output buffer, then there is a change that it
   // still has internal data to emit, and this flag is set.
   bool filter_needs_more_output_space_;
 
-  // When we filter data, we receive data into the filter buffers.  After
-  // processing the filtered data, we return the data in the caller's buffer.
-  // While the async IO is in progress, we save the user buffer here, and
-  // when the IO completes, we fill this in.
-  scoped_refptr<IOBuffer> filtered_read_buffer_;
-  int filtered_read_buffer_len_;
-
   // We keep a pointer to the read buffer while asynchronous reads are
   // in progress, so we are able to pass those bytes to job observers.
   scoped_refptr<IOBuffer> raw_read_buffer_;
 
   // Used by HandleResponseIfNecessary to track whether we've sent the
   // OnResponseStarted callback and potentially redirect callbacks as well.
   bool has_handled_response_;
 
   // Expected content size
   int64_t expected_content_size_;
 
   // Set when a redirect is deferred.
   RedirectInfo deferred_redirect_info_;
 
   // The network delegate to use with this request, if any.
   NetworkDelegate* network_delegate_;
 
   // The value from GetTotalReceivedBytes() the last time
   // MaybeNotifyNetworkBytes() was called. Used to calculate how bytes have been
   // newly received since the last notification.
   int64_t last_notified_total_received_bytes_;
 
   // The value from GetTotalSentBytes() the last time MaybeNotifyNetworkBytes()
   // was called. Used to calculate how bytes have been newly sent since the last
   // notification.
   int64_t last_notified_total_sent_bytes_;
 
+  ReadRawCompleteCallback read_raw_callback_;
+
+  // Raw network bytes read from job subclass.
+  size_t raw_bytes_read_;
+
+  size_t postfilter_bytes_read_;
+
   base::WeakPtrFactory<URLRequestJob> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(URLRequestJob);
 };
 
 }  // namespace net
 
 #endif  // NET_URL_REQUEST_URL_REQUEST_JOB_H_