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

net/filter/sdch_policy_delegate.h

+// Copyright 2016 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_FILTER_SDCH_POLICY_DELEGATE_H_
+#define NET_FILTER_SDCH_POLICY_DELEGATE_H_
+
+#include <memory>
+
+#include "base/macros.h"
+#include "base/supports_user_data.h"
+#include "net/base/net_export.h"
+#include "net/base/sdch_manager.h"
+#include "net/filter/sdch_source_stream.h"
+#include "net/log/net_log.h"
+#include "url/gurl.h"
+
+namespace net {
+
+class SdchSourceStream;
+
+// This class ascribes to the SdchSourceStream::Delegate interface to implement
+// the SDCH error-handling and stats-gathering policy. The Context object
+// supplies details about the request needed for this object to make
+// error-handling decisions. See the SdchSourceStream::Delegate documentation
+// for more details.
+class NET_EXPORT_PRIVATE SdchPolicyDelegate
+    : public SdchSourceStream::Delegate {
+ public:
+  class Context {
+   public:
+    enum StatisticSelector {
+      SDCH_DECODE,
+      SDCH_PASSTHROUGH,
+      SDCH_EXPERIMENT_DECODE,
+      SDCH_EXPERIMENT_HOLDBACK,
+    };
+
+    virtual ~Context() {}
+    virtual bool GetMimeType(std::string* mime_type) const = 0;
+    virtual bool GetURL(GURL* url) const = 0;
+    virtual bool IsCachedContent() const = 0;
+    virtual SdchManager* GetSdchManager() const = 0;
+    virtual SdchManager::DictionarySet* SdchDictionariesAdvertised() const = 0;
+    // virtual int64_t GetByteReadCount() const = 0;
+    virtual int GetResponseCode() const = 0;
+    virtual const BoundNetLog& GetNetLog() const = 0;
+  };
+
+  SdchPolicyDelegate(std::unique_ptr<Context> context);
+
+  ~SdchPolicyDelegate() override;
+
+  // SdchSourceStream::Delegate implementation.
+  bool OnDictionaryError(SdchSourceStream* source) override;
+  bool OnDecodingError(SdchSourceStream* source) override;
+  bool OnGetDictionary(const std::string& server_id,
+                       const std::string** text) override;
+
+ private:
+  // Issues a meta-refresh if the context's MIME type supports it, and returns
+  // whether a refresh was issued. As a side-effect, blacklists the context's
+  // domain either temporarily or permanently.
+  bool IssueMetaRefreshIfPossible(SdchSourceStream* source);
+
+  // Logs an SDCH failure. This logs events in UMA and the net log in
+  // |context_|, but has no side-effects on this class or the stream.
+  void LogSdchProblem(SdchProblemCode problem);
+
+  bool dictionary_requested_;
+
+  std::unique_ptr<Context> context_;
+  // If the response was encoded with a dictionary different than those
+  // advertised (e.g. a cached response using an old dictionary), this
+  // variable preserves that dictionary from deletion during decoding.
+  std::unique_ptr<SdchManager::DictionarySet> unexpected_dictionary_set_;
+
+  DISALLOW_COPY_AND_ASSIGN(SdchPolicyDelegate);
+};
+
+}  // namespace net
+
+#endif  // NET_FILTER_SDCH_POLICY_DELEGATE_H_