chrome/browser/media_galleries/fileapi/safe_media_metadata_parser.h

// Copyright 2014 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 CHROME_BROWSER_MEDIA_GALLERIES_FILEAPI_SAFE_MEDIA_METADATA_PARSER_H_
#define CHROME_BROWSER_MEDIA_GALLERIES_FILEAPI_SAFE_MEDIA_METADATA_PARSER_H_

#include <stdint.h>

#include <memory>
#include <string>
#include <vector>

#include "base/callback.h"
#include "base/compiler_specific.h"
#include "base/macros.h"
#include "base/memory/weak_ptr.h"
#include "chrome/common/extensions/api/media_galleries.h"
#include "chrome/common/extensions/media_parser.mojom.h"
#include "chrome/common/media_galleries/metadata_types.h"
#include "content/public/browser/utility_process_host.h"
#include "content/public/browser/utility_process_host_client.h"

namespace IPC {
class Message;
}

class Profile;

namespace metadata {

// Parses the media metadata of a Blob safely in a utility process. This class
// expects the MIME type of the Blob to be already determined. It spawns a
// utility process to do further MIME-type specific metadata extraction.
// All public methods and callbacks of this class run on the UI thread.
class SafeMediaMetadataParser : public content::UtilityProcessHostClient {
 public:
  // |metadata_dictionary| is owned by the callback.
  typedef base::Callback<void(
      bool parse_success,
      std::unique_ptr<base::DictionaryValue> metadata_dictionary,
      std::unique_ptr<std::vector<AttachedImage>> attached_images)>
      DoneCallback;

  SafeMediaMetadataParser(Profile* profile,
                          const std::string& blob_uuid,
                          int64_t blob_size,
                          const std::string& mime_type,
                          bool get_attached_images);

  // Should be called on the UI thread. |callback| also runs on the UI thread.
  void Start(const DoneCallback& callback);

 private:
  enum ParserState {
    INITIAL_STATE,
    STARTED_PARSING_STATE,
    FINISHED_PARSING_STATE,
  };

  // Private because content::UtilityProcessHostClient is ref-counted.
  ~SafeMediaMetadataParser() override;

  // Launches the utility process.  Must run on the IO thread.
  void StartWorkOnIOThread(const DoneCallback& callback);

  // Mojo callback if the utility process or metadata parse requests fail.
  // Runs on the IO thread.
  void ParseMediaMetadataFailed();

  // Mojo callback from utility process when it finishes parsing metadata.
  // Runs on the IO thread.
  void ParseMediaMetadataDone(
      bool parse_success,
      std::unique_ptr<base::DictionaryValue> metadata_dictionary,
      const std::vector<AttachedImage>& attached_images);

  // Sequence of functions that bounces from the IO thread to the UI thread to
  // read the blob data, then sends the data back to the utility process.
  void OnUtilityProcessRequestBlobBytes(int64_t request_id,
                                        int64_t byte_start,
                                        int64_t length);
  void StartBlobReaderOnUIThread(int64_t request_id,
                                 int64_t byte_start,
                                 int64_t length);
  void OnBlobReaderDoneOnUIThread(int64_t request_id,
                                  std::unique_ptr<std::string> data,
                                  int64_t /* blob_total_size */);
  void FinishRequestBlobBytes(int64_t request_id,
                              std::unique_ptr<std::string> data);

  // UtilityProcessHostClient implementation.
  // Runs on the IO thread.
  bool OnMessageReceived(const IPC::Message& message) override;

  // All member variables are only accessed on the IO thread.
  Profile* const profile_;
  const std::string blob_uuid_;
  const int64_t blob_size_;
  const std::string mime_type_;
  bool get_attached_images_;

  DoneCallback callback_;

  base::WeakPtr<content::UtilityProcessHost> utility_process_host_;

  extensions::mojom::MediaParserPtr interface_;

  // Verifies the messages from the utility process came at the right time.
  // Initialized on the UI thread, but only accessed on the IO thread.
  ParserState parser_state_;

  DISALLOW_COPY_AND_ASSIGN(SafeMediaMetadataParser);
};

}  // namespace metadata

#endif  // CHROME_BROWSER_MEDIA_GALLERIES_FILEAPI_SAFE_MEDIA_METADATA_PARSER_H_