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      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
     60