text: // 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/webui/url_data_source_impl.h"
  
  #include "base/bind.h"
  #include "base/memory/ref_counted_memory.h"
  #include "base/string_util.h"
  #include "content/browser/webui/url_data_manager_backend.h"
  #include "content/public/browser/browser_thread.h"
  #include "content/public/browser/url_data_source.h"
  
  namespace content {
  
  URLDataSourceImpl::URLDataSourceImpl(const std::string& source_name,
                                       URLDataSource* source)
      : source_name_(source_name),
        backend_(NULL),
        source_(source) {
  }
  
  URLDataSourceImpl::~URLDataSourceImpl() {
  }
  
  void URLDataSourceImpl::SendResponse(
      int request_id,
      base::RefCountedMemory* bytes) {
    // Take a ref-pointer on entry so byte->Release() will always get called.
    scoped_refptr<base::RefCountedMemory> bytes_ptr(bytes);
    if (URLDataManager::IsScheduledForDeletion(this)) {
      // We're scheduled for deletion. Servicing the request would result in
      // this->AddRef being invoked, even though the ref count is 0 and 'this' is
      // about to be deleted. If the AddRef were allowed through, when 'this' is
      // released it would be deleted again.
      //
      // This scenario occurs with DataSources that make history requests. Such
      // DataSources do a history query in |StartDataRequest| and the request is
      // live until the object is deleted (history requests don't up the ref
      // count). This means it's entirely possible for the DataSource to invoke
      // |SendResponse| between the time when there are no more refs and the time
      // when the object is deleted.
      return;
    }
    BrowserThread::PostTask(
        BrowserThread::IO, FROM_HERE,
        base::Bind(&URLDataSourceImpl::SendResponseOnIOThread, this, request_id,
                   bytes_ptr));
  }
  
  void URLDataSourceImpl::SendResponseOnIOThread(
      int request_id,
      scoped_refptr<base::RefCountedMemory> bytes) {
    DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
    if (backend_)
      backend_->DataAvailable(request_id, bytes);
  }
  
  }  // namespace content
  