Refactor FileIO to the new design

ppapi/shared_impl/file_io_state_manager.h

Index: ppapi/shared_impl/file_io_state_manager.h
diff --git a/ppapi/shared_impl/file_io_state_manager.h b/ppapi/shared_impl/file_io_state_manager.h
new file mode 100644
index 0000000000000000000000000000000000000000..1c4fa1a9cdad83755377184c911b8e1f0bb109b4
--- /dev/null
+++ b/ppapi/shared_impl/file_io_state_manager.h
@@ -0,0 +1,68 @@
+// 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_SHARED_IMPL_FILE_IO_STATE_MANAGER_H_
+#define PPAPI_SHARED_IMPL_FILE_IO_STATE_MANAGER_H_
+
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+#include "ppapi/c/pp_stdint.h"
+#include "ppapi/shared_impl/ppapi_shared_export.h"
+
+namespace ppapi {
+
+// FileIOStateManager is a helper class that maintains the state of operations.
+// For example, some operations are mutually exclusive, meaning that an
+// operation could be rejected because of the current pending operation. Also,
+// most of the operations only work when the file has been opened.
+class PPAPI_SHARED_EXPORT FileIOStateManager {
+ public:
+  FileIOStateManager();
+  ~FileIOStateManager();
+
+  enum OperationType {
+    // There is no pending operation right now.
+    OPERATION_NONE,
+
+    // If there are pending reads, any other kind of async operation is not
+    // allowed.
+    OPERATION_READ,
+
+    // If there are pending writes, any other kind of async operation is not
+    // allowed.
+    OPERATION_WRITE,
+
+    // If there is a pending operation that is neither read nor write, no
+    // further async operation is allowed.
+    OPERATION_EXCLUSIVE
+  };
+
+  OperationType get_pending_operation() const { return pending_op_; }
+
+  void SetOpenSucceed();
+
+  // Called at the beginning of each operation. It is responsible to make sure
+  // that state is correct. For example, some operations are only valid after
+  // the file is opened, or operations might need to run exclusively.
+  //
+  // It returns |PP_OK| on success, or |PP_ERROR_...| for various reasons.
+  int32_t CheckOperationState(OperationType new_op, bool should_be_open);
+
+  // Marks the state of current operations as started or finished.
+  void SetPendingOperation(OperationType op);
+  void SetOperationFinished();
+
+ private:
+  int num_pending_ops_;
+  OperationType pending_op_;
+
+  // Set to true when the file has been successfully opened.
+  bool file_open_;
+
+  DISALLOW_COPY_AND_ASSIGN(FileIOStateManager);
+};
+
+}  // namespace ppapi
+
+#endif  // PPAPI_SHARED_IMPL_FILE_IO_STATE_MANAGER_H_