content/browser/webui/url_data_source_impl.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "content/browser/webui/url_data_source_impl.h"
   6
   7 #include "base/bind.h"
   8 #include "base/memory/ref_counted_memory.h"
   9 #include "base/strings/string_util.h"
  10 #include "content/browser/webui/url_data_manager_backend.h"
  11 #include "content/public/browser/browser_thread.h"
  12 #include "content/public/browser/url_data_source.h"
  13
  14 namespace content {
  15
  16 URLDataSourceImpl::URLDataSourceImpl(const std::string& source_name,
  17                                      URLDataSource* source)
  18     : source_name_(source_name),
  19       backend_(NULL),
  20       source_(source) {
  21 }
  22
  23 URLDataSourceImpl::~URLDataSourceImpl() {
  24 }
  25
  26 void URLDataSourceImpl::SendResponse(
  27     int request_id,
  28     base::RefCountedMemory* bytes) {
  29   // Take a ref-pointer on entry so byte->Release() will always get called.
  30   scoped_refptr<base::RefCountedMemory> bytes_ptr(bytes);
  31   if (URLDataManager::IsScheduledForDeletion(this)) {
  32     // We're scheduled for deletion. Servicing the request would result in
  33     // this->AddRef being invoked, even though the ref count is 0 and 'this' is
  34     // about to be deleted. If the AddRef were allowed through, when 'this' is
  35     // released it would be deleted again.
  36     //
  37     // This scenario occurs with DataSources that make history requests. Such
  38     // DataSources do a history query in |StartDataRequest| and the request is
  39     // live until the object is deleted (history requests don't up the ref
  40     // count). This means it's entirely possible for the DataSource to invoke
  41     // |SendResponse| between the time when there are no more refs and the time
  42     // when the object is deleted.
  43     return;
  44   }
  45   BrowserThread::PostTask(
  46       BrowserThread::IO, FROM_HERE,
  47       base::Bind(&URLDataSourceImpl::SendResponseOnIOThread, this, request_id,
  48                  bytes_ptr));
  49 }
  50
  51 void URLDataSourceImpl::SendResponseOnIOThread(
  52     int request_id,
  53     scoped_refptr<base::RefCountedMemory> bytes) {
  54   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
  55   if (backend_)
  56     backend_->DataAvailable(request_id, bytes.get());
  57 }
  58
  59 }  // namespace content