file_io_resource.h

// 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.

#ifndef PPAPI_PROXY_FILE_IO_RESOURCE_H_
#define PPAPI_PROXY_FILE_IO_RESOURCE_H_

#include <stdint.h>

#include <memory>
#include <string>

#include "base/files/file.h"
#include "base/macros.h"
#include "base/memory/ref_counted.h"
#include "ppapi/c/private/pp_file_handle.h"
#include "ppapi/proxy/connection.h"
#include "ppapi/proxy/plugin_resource.h"
#include "ppapi/proxy/ppapi_proxy_export.h"
#include "ppapi/shared_impl/file_io_state_manager.h"
#include "ppapi/shared_impl/resource.h"
#include "ppapi/shared_impl/scoped_pp_resource.h"
#include "ppapi/thunk/ppb_file_io_api.h"

namespace ppapi {

class TrackedCallback;

namespace proxy {

class PPAPI_PROXY_EXPORT FileIOResource
    : public PluginResource,
      public thunk::PPB_FileIO_API {
 public:
  FileIOResource(Connection connection, PP_Instance instance);
  ~FileIOResource() override;

  // Resource overrides.
  thunk::PPB_FileIO_API* AsPPB_FileIO_API() override;

  // PPB_FileIO_API implementation.
  int32_t Open(PP_Resource file_ref,
               int32_t open_flags,
               scoped_refptr<TrackedCallback> callback) override;
  int32_t Query(PP_FileInfo* info,
                scoped_refptr<TrackedCallback> callback) override;
  int32_t Touch(PP_Time last_access_time,
                PP_Time last_modified_time,
                scoped_refptr<TrackedCallback> callback) override;
  int32_t Read(int64_t offset,
               char* buffer,
               int32_t bytes_to_read,
               scoped_refptr<TrackedCallback> callback) override;
  int32_t ReadToArray(int64_t offset,
                      int32_t max_read_length,
                      PP_ArrayOutput* array_output,
                      scoped_refptr<TrackedCallback> callback) override;
  int32_t Write(int64_t offset,
                const char* buffer,
                int32_t bytes_to_write,
                scoped_refptr<TrackedCallback> callback) override;
  int32_t SetLength(int64_t length,
                    scoped_refptr<TrackedCallback> callback) override;
  int64_t GetMaxWrittenOffset() const override;
  int64_t GetAppendModeWriteAmount() const override;
  void SetMaxWrittenOffset(int64_t max_written_offset) override;
  void SetAppendModeWriteAmount(int64_t append_mode_write_amount) override;
  int32_t Flush(scoped_refptr<TrackedCallback> callback) override;
  void Close() override;
  int32_t RequestOSFileHandle(PP_FileHandle* handle,
                              scoped_refptr<TrackedCallback> callback) override;

  // FileHolder is used to guarantee that file operations will have a valid FD
  // to operate on, even if they're in a different thread.
  // If instead we just passed the raw FD, the FD could be closed before the
  // file operation has a chance to run. It could interact with an invalid FD,
  // or worse, the FD value could be reused if another file is opened quickly
  // (POSIX is required to provide the lowest available value when opening a
  // file). This could result in strange problems such as writing data to the
  // wrong file.
  //
  // Operations that run on a background thread should hold one of these to
  // ensure they have a valid file descriptor. The file handle is only closed
  // when the last reference to the FileHolder is removed, so we are guaranteed
  // to operate on the correct file descriptor. It *is* still possible that the
  // FileIOResource will be destroyed and "Abort" callbacks just before the
  // operation does its task (e.g., Reading). In that case, we might for example
  // Read from a file even though the FileIO has been destroyed and the plugin's
  // callback got a PP_ERROR_ABORTED result. In the case of a write, we could
  // write some data to the file despite the plugin receiving a
  // PP_ERROR_ABORTED instead of a successful result.
  class FileHolder : public base::RefCountedThreadSafe<FileHolder> {
   public:
    explicit FileHolder(PP_FileHandle file_handle);
    base::File* file() {
      return &file_;
    }
    static bool IsValid(
        const scoped_refptr<FileIOResource::FileHolder>& handle);
   private:
    friend class base::RefCountedThreadSafe<FileHolder>;
    ~FileHolder();
    base::File file_;
  };

  scoped_refptr<FileHolder> file_holder() {
    return file_holder_;
  }

 private:
  // Class to perform file query operations across multiple threads.
  class QueryOp : public base::RefCountedThreadSafe<QueryOp> {
   public:
    explicit QueryOp(scoped_refptr<FileHolder> file_holder);

    // Queries the file. Called on the file thread (non-blocking) or the plugin
    // thread (blocking). This should not be called when we hold the proxy lock.
    int32_t DoWork();

    const base::File::Info& file_info() const { return file_info_; }

   private:
    friend class base::RefCountedThreadSafe<QueryOp>;
    ~QueryOp();

    scoped_refptr<FileHolder> file_holder_;
    base::File::Info file_info_;
  };

  // Class to perform file read operations across multiple threads.
  class ReadOp : public base::RefCountedThreadSafe<ReadOp> {
   public:
    ReadOp(scoped_refptr<FileHolder> file_holder,
           int64_t offset,
           int32_t bytes_to_read);

    // Reads the file. Called on the file thread (non-blocking) or the plugin
    // thread (blocking). This should not be called when we hold the proxy lock.
    int32_t DoWork();

    char* buffer() const { return buffer_.get(); }

   private:
    friend class base::RefCountedThreadSafe<ReadOp>;
    ~ReadOp();

    scoped_refptr<FileHolder> file_holder_;
    int64_t offset_;
    int32_t bytes_to_read_;
    std::unique_ptr<char[]> buffer_;
  };

  // Class to perform file write operations across multiple threads.
  class WriteOp : public base::RefCountedThreadSafe<WriteOp> {
   public:
    WriteOp(scoped_refptr<FileHolder> file_holder,
            int64_t offset,
            std::unique_ptr<char[]> buffer,
            int32_t bytes_to_write,
            bool append);

    // Writes the file. Called on the file thread (non-blocking) or the plugin
    // thread (blocking). This should not be called when we hold the proxy lock.
    int32_t DoWork();

   private:
    friend class base::RefCountedThreadSafe<WriteOp>;
    ~WriteOp();

    scoped_refptr<FileHolder> file_holder_;
    int64_t offset_;
    std::unique_ptr<char[]> buffer_;
    int32_t bytes_to_write_;
    bool append_;
  };

  void OnRequestWriteQuotaComplete(int64_t offset,
                                   std::unique_ptr<char[]> buffer,
                                   int32_t bytes_to_write,
                                   scoped_refptr<TrackedCallback> callback,
                                   int64_t granted);
  void OnRequestSetLengthQuotaComplete(int64_t length,
                                       scoped_refptr<TrackedCallback> callback,
                                       int64_t granted);

  int32_t ReadValidated(int64_t offset,
                        int32_t bytes_to_read,
                        const PP_ArrayOutput& array_output,
                        scoped_refptr<TrackedCallback> callback);
  int32_t WriteValidated(int64_t offset,
                         const char* buffer,
                         int32_t bytes_to_write,
                         scoped_refptr<TrackedCallback> callback);
  void SetLengthValidated(int64_t length,
                          scoped_refptr<TrackedCallback> callback);

  // Completion tasks for file operations that are done in the plugin.
  int32_t OnQueryComplete(scoped_refptr<QueryOp> query_op,
                          PP_FileInfo* info,
                          int32_t result);
  int32_t OnReadComplete(scoped_refptr<ReadOp> read_op,
                         PP_ArrayOutput array_output,
                         int32_t result);
  int32_t OnWriteComplete(int32_t result);

  // Reply message handlers for operations that are done in the host.
  void OnPluginMsgGeneralComplete(scoped_refptr<TrackedCallback> callback,
                                  const ResourceMessageReplyParams& params);
  void OnPluginMsgOpenFileComplete(scoped_refptr<TrackedCallback> callback,
                                   const ResourceMessageReplyParams& params,
                                   PP_Resource quota_file_system,
                                   int64_t max_written_offset);
  void OnPluginMsgRequestOSFileHandleComplete(
      scoped_refptr<TrackedCallback> callback,
      PP_FileHandle* output_handle,
      const ResourceMessageReplyParams& params);

  scoped_refptr<FileHolder> file_holder_;
  PP_FileSystemType file_system_type_;
  scoped_refptr<Resource> file_system_resource_;
  FileIOStateManager state_manager_;

  scoped_refptr<Resource> file_ref_;

  int32_t open_flags_;
  int64_t max_written_offset_;
  int64_t append_mode_write_amount_;
  bool check_quota_;
  bool called_close_;

  DISALLOW_COPY_AND_ASSIGN(FileIOResource);
};

}  // namespace proxy
}  // namespace ppapi

#endif  // PPAPI_PROXY_FILE_IO_RESOURCE_H_