---
title: CFAllocatorPreferredSizeCallBack
framework: corefoundation
role: symbol
role_heading: Type Alias
path: corefoundation/cfallocatorpreferredsizecallback
---

# CFAllocatorPreferredSizeCallBack

A prototype for a function callback that gives the size of memory likely to be allocated, given a certain request.

## Declaration

```swift
typealias CFAllocatorPreferredSizeCallBack = (CFIndex, CFOptionFlags, UnsafeMutableRawPointer?) -> CFIndex
```

## Parameters

- `size`: The amount of memory requested.
- `hint`: A bitfield that is currently not used (always set to 0).
- `info`: An untyped pointer to program-defined data.

## Return Value

Return Value The actual size the allocator is likely to allocate given this request.

## Discussion

Discussion A prototype for a function callback that determines whether there is enough free memory to satisfy a request. In implementing this function, return the actual size the allocator is likely to allocate given a request for a block of memory of size size. The hint argument is a bitfield that you should currently not use.

## See Also

### Callbacks

- [CFAllocatorAllocateCallBack](corefoundation/cfallocatorallocatecallback.md)
- [CFAllocatorCopyDescriptionCallBack](corefoundation/cfallocatorcopydescriptioncallback.md)
- [CFAllocatorDeallocateCallBack](corefoundation/cfallocatordeallocatecallback.md)
- [CFAllocatorReallocateCallBack](corefoundation/cfallocatorreallocatecallback.md)
- [CFAllocatorReleaseCallBack](corefoundation/cfallocatorreleasecallback.md)
- [CFAllocatorRetainCallBack](corefoundation/cfallocatorretaincallback.md)