What Is Storage?

[アーティクル]
09/29/2011

Storage refers to memory locations used for reading and writing data.

Storage Locations
Title Storage
User Storage

Storage Locations

When programming with the XNA Framework, you read files from two general locations:

Title storage is where the game executable and support files (shaders, meshes, textures, and so on) are located.
User storage is the space a player provides for game data (such as saves) that is either locked to a particular profile or available to all players.

Title Storage

Title storage refers to the read-only storage in the default game storage location, including the game executable and all other files packaged with the game. Data in title storage may be accessed through one of two ways:

Content Pipeline

Typically, game assets (such as textures, shaders, media, and custom data) are accessed through the Content Pipeline.

The assets managed through these facilities are not accessed directly as files, but instead are loaded and unloaded through ContentManager by reference to the names they were given at build-time.

Your XNA Game Studio game should use the Content Pipeline, as it offers the most flexible and efficient facilities to manage these assets, and assures speedy operation of your game.

File Stream Access

As noted, your game should use the Content Pipeline to manage its game assets. There may be exceptional cases in which you'll want to manage your own game data—for example, if you have a preexisting content manager that you want to use with XNA Game Studio, or if you otherwise want stream level access to arbitrary game data files.

You can add arbitrary data files to title storage at build time, and they'll be available to your game during runtime through TitleContainer, which provides stream level access to any files in this location.

The following sections describe how to add files to, and read files from, title storage through file stream access:

User Storage

User storage refers to the read-write storage supported by the game platform for saving information from the game at runtime. The data can be associated with a particular player's profile, or available to all players.

Note

On Windows Phone, writable user storage is handled by Silverlight, not by XNA Game Studio. For more information about saving game data on Windows Phone, see Writing Data (Windows Phone).

Access User Storage

Accessing user storage is performed in two steps:

To access user storage

Retrieve a StorageDevice object to access the user storage device.

The BeginShowSelector method launches a dialog box that prompts the user to choose a storage device (for example, a memory unit or disk). This method works asynchronously, notifying the caller with an IAsyncResult or a callback method when the user has chosen a device.

When the operation is complete, the StorageDevice object for the user selected device is retrieved through the EndShowSelector method.

For an example, see Getting a StorageDevice Asynchronously.
Access the user storage device to read or write.

The StorageContainer instance provided by BeginOpenContainer provides access to the selected device. Use System.IO objects, such as the File object, to open, copy, rename, or delete files.

Note

Open the StorageContainer before reading file data. Not doing so will result in an InvalidOperationException exception.

For an example, see Saving Data to a Save Game File.

Implementation on Xbox 360

Changes to the files within a StorageContainer on Xbox 360 do not take effect until the StorageContainer is disposed. For this reason, only one StorageContainer can be open on the same device for the same profile.

Before opening a StorageContainer on a device, ensure all previous StorageContainer objects opened for that profile have been disposed. To dispose a StorageContainer, call Dispose.

Implementation on Windows

User storage is in the My Documents folder of the user who is currently logged in, in the SavedGames folder. A subfolder is created for each game according to the titleName passed to the BeginOpenContainer method. When no PlayerIndex is specified, content is saved in the AllPlayers folder. When a PlayerIndex is specified, the content is saved in the Player1, Player2, Player3, or Player4 folder, depending on which PlayerIndex was passed to BeginShowSelector.

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