# CGDataProviderGetBytesCallback A callback function that copies from a provider data stream into a Core Graphics buffer. ``` typealias CGDataProviderGetBytesCallback = (UnsafeMutableRawPointer?, UnsafeMutableRawPointer, Int) -> Int ``` ## Parameters `info` A generic pointer to private data shared among your callback functions. This is the same pointer you supplied to [`init(version:getBytes:skipForward:rewind:releaseInfo:)`](/documentation/CoreGraphics/CGDataProviderSequentialCallbacks/init(version:getBytes:skipForward:rewind:releaseInfo:)). `buffer` The Core Graphics buffer into which you copy the specified number of bytes. `count` The number of bytes to copy. ## Return Value The number of bytes copied. If no more data can be written to the buffer, you should return `0`. ## Discussion When Core Graphics is ready to receive data from the provider data stream, your function is called. It should copy the specified number of bytes into `buffer`. For information on how to associate your callback function with a data provider, see [`CGDataProvider`](/documentation/CoreGraphics/CGDataProvider) and [`CGDataProviderSequentialCallbacks`](/documentation/CoreGraphics/CGDataProviderSequentialCallbacks). --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)