---
title: "CFReadStreamCreateWithBytesNoCopy(_:_:_:_:)"
framework: corefoundation
role: symbol
role_heading: Function
path: "corefoundation/cfreadstreamcreatewithbytesnocopy(_:_:_:_:)"
---

# CFReadStreamCreateWithBytesNoCopy(_:_:_:_:)

Creates a readable stream for a block of memory.

## Declaration

```swift
func CFReadStreamCreateWithBytesNoCopy(_ alloc: CFAllocator!, _ bytes: UnsafePointer<UInt8>!, _ 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

Return Value The new read stream, or NULL on failure. Ownership follows the The Create Rule.

## Discussion

Discussion You must open the stream, using CFReadStreamOpen(_:), before reading from it.

## See Also

### Creating a Read Stream

- [CFReadStreamCreateWithFile(_:_:)](corefoundation/cfreadstreamcreatewithfile(_:_:).md)