# CMBlockBufferAccessDataBytes(_:atOffset:length:temporaryBlock:returnedPointerOut:) Accesses potentially noncontiguous data in a block buffer. ``` func CMBlockBufferAccessDataBytes(_ theBuffer: CMBlockBuffer, atOffset offset: Int, length: Int, temporaryBlock: UnsafeMutableRawPointer, returnedPointerOut: UnsafeMutablePointer?>) -> OSStatus ``` ## Parameters `theBuffer` `CMBlockBuffer` to operate on. Must not be `NULL`. `offset` Offset within the `CMBlockBuffer's` offset range. `length` Desired number of bytes to access at offset. `temporaryBlock` A piece of memory, assumed to be at least `length` bytes in size. Must not be `NULL` `returnedPointerOut` Receives `NULL` if the desired amount of data could not be accessed at the given offset. Receives non-`NULL` if it could. The value returned is either a direct pointer into the `CMBlockBuffer` or to the `temporaryBlock`. Must not be `NULL`. ## Return Value Returns `kCMBlockBufferNoErr` if the desired amount of data could be accessed at the given offset. ## Discussion This routine is use for accessing contiguous and noncontiguous data. If the data is contiguous, the routine will return a pointer to the given `CMBlockBuffer`. If the data is not contiguous, the routine will copy the data into a temporary block and a pointer to this block will be returned. --- 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)