# CFStringCreateWithBytesNoCopy(_:_:_:_:_:_:) Creates a string from a buffer, containing characters in a specified encoding, that might serve as the backing store for the new string. ``` func CFStringCreateWithBytesNoCopy(_ alloc: CFAllocator!, _ bytes: UnsafePointer!, _ numBytes: CFIndex, _ encoding: CFStringEncoding, _ isExternalRepresentation: Bool, _ contentsDeallocator: CFAllocator!) -> CFString! ``` ## Parameters `alloc` The allocator to use to allocate memory for the new CFString object. Pass `NULL` or [`kCFAllocatorDefault`](/documentation/CoreFoundation/kCFAllocatorDefault) to use the current default allocator. `bytes` A buffer containing characters in the encoding specified by `encoding`. The buffer must *not* contain a length byte (as in Pascal buffers) or any terminating `NULL` character (as in C buffers). `numBytes` The number of bytes in `bytes`. `encoding` The character encoding of `bytes`. `isExternalRepresentation` `true` if the characters in the byte buffer are in an “external representation” format—that is, whether the buffer contains a BOM (byte order marker). This is usually the case for bytes that are read in from a text file or received over the network. Otherwise, pass `false`. `contentsDeallocator` The allocator to use to deallocate `bytes` when it is no longer needed. You can pass `NULL` or [`kCFAllocatorDefault`](/documentation/CoreFoundation/kCFAllocatorDefault) to request the default allocator for this purpose. If the buffer does not need to be deallocated, or if you want to assume responsibility for deallocating the buffer (and not have the string deallocate it), pass [`kCFAllocatorNull`](/documentation/CoreFoundation/kCFAllocatorNull). ## Return Value A new string whose contents are `bytes`. 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 This function takes an explicit length, and allows you to specify whether the data is an external format—that is, whether to pay attention to the BOM character (if any) and do byte swapping if necessary ### Special Considerations If an error occurs during the creation of the string, then `bytes` is not deallocated. In this case, the caller is responsible for freeing the buffer. This allows the caller to continue trying to create a string with the buffer, without having the buffer deallocated. --- 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)