DuplicateContentResourceHandler to monitor resources and track how many times th…

content/browser/renderer_host/duplicate_resource_handler.cc

+// 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.
+
+#include "content/browser/renderer_host/duplicate_resource_handler.h"
+
+#include <string>
+
+#include "base/logging.h"
+#include "base/metrics/histogram.h"
+#include "content/browser/renderer_host/resource_request_info_impl.h"
+#include "net/base/io_buffer.h"
+#include "third_party/smhasher/src/MurmurHash3.h"
+
+
+namespace content {
+
+namespace{
+ 
+std::set<uint32>* GetSetOfHashes() {
+  static std::set<uint32> seen_resources;
+  return &seen_resources;
+}
+
+}  // namespace
+
+DuplicateResourceHandler::DuplicateResourceHandler(
+    scoped_ptr<ResourceHandler> next_handler,
+    net::URLRequest* request)
+    : LayeredResourceHandler(next_handler.Pass()),
+      bytes_read_(0),
+      bytes_hit_(0),
+      bytes_miss_(0),
+      read_buffer_size_(0),  // keep track of bytes in read buffer
+      read_buffer_(new net::IOBuffer(kReadBufSize)),
+      request_(request) {
+}
+
+DuplicateResourceHandler::~DuplicateResourceHandler() {
+}
+
+/*bool DuplicateResourceHandler::OnWillStart(int request_id, 
+                                           const GURL& url, 
+                                           bool* defer) {
+  return true;
+}*/
+
+bool DuplicateResourceHandler::OnWillRead(int request_id, net::IOBuffer** buf, 
+                                          int* buf_size, int min_size) {
+  DCHECK_EQ(-1, min_size);
+
+  *buf = read_buffer_.get(); 
+  *buf_size = kReadBufSize;
+  return true;

[gavinp, 2012/07/13 21:16:04]

I'm pretty sure you always want to pass through.

+
+}
+
+bool DuplicateResourceHandler::OnReadCompleted(int request_id, int bytes_read,
+                                              bool* defer) {
+  /*if (!next_handler_->OnReadCompleted(request_id, bytes_read, defer))
+    return false;*/
+  
+  //DVLOG(4) << "read_buffer_ is " << read_buffer_.get();
+  //DVLOG(4) << "read_buffer_->data() is " << read_buffer_->data();
+
+  // find hash of resource
+  uint32 buf_hash;
+  MurmurHash3_x86_32(read_buffer_->data(), bytes_read, 0x0, &buf_hash);
+  
+
+  const bool did_we_find_it = GetSetOfHashes()->find(buf_hash) != GetSetOfHashes()->end();
+  UMA_HISTOGRAM_BOOLEAN("Duplicate.HitRate", did_we_find_it);  
+  
+  // if element is in hash
+  if (did_we_find_it) {
+    bytes_hit_ += bytes_read;
+
+  } else {
+    bytes_miss_ += bytes_read;
+    GetSetOfHashes()->insert(buf_hash);
+  }
+
+  bytes_read_ += bytes_read;
+  return true;
+}
+
+bool DuplicateResourceHandler::OnResponseCompleted(
+    int request_id,
+    const net::URLRequestStatus& status,
+    const std::string& security_info) {
+  
+  read_buffer_ = NULL;
+  return next_handler_->OnResponseCompleted(request_id, status, security_info);
+}
+
+}  //namespace content