# CFReadStreamCreateWithBytesNoCopy(_:_:_:_:) Creates a readable stream for a block of memory. ``` func CFReadStreamCreateWithBytesNoCopy(_ alloc: CFAllocator!, _ bytes: UnsafePointer!, _ length: CFIndex, _ bytesDeallocator: CFAllocator!) -> CFReadStream! ``` ## Parameters `alloc` The allocator to use to allocate memory for the new object. Pass `NULL` or kCFAllocatorDefault to use the current default allocator. `bytes` The memory buffer to read. This memory must exist for the lifetime of the new stream. `length` The size of `bytes`. `bytesDeallocator` The allocator to use to deallocate `bytes` when the stream is deallocated. Pass kCFAllocatorNull to prevent the stream from deallocating `bytes`. ## Return Value The new read stream, or `NULL` on failure. Ownership follows the [The Create Rule](https://developer.apple.com/library/archive/documentation/CoreFoundation/Conceptual/CFMemoryMgmt/Concepts/Ownership.html#//apple_ref/doc/uid/20001148-103029). ## Discussion You must open the stream, using [`CFReadStreamOpen(_:)`](/documentation/CoreFoundation/CFReadStreamOpen(_:)), before reading from it. --- 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)