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# CMBlockBufferCustomBlockSource

A structure to support custom memory allocation and deallocation for a block used in a block buffer.

```
struct CMBlockBufferCustomBlockSource
```

## Overview

This structure allows a client to provide a custom facility for obtaining the memory block to be used in a `CMBlockBuffer`. You use this structure with functions that accept a memory block allocator.

## Topics

### Initializers

[`init()`](/documentation/CoreMedia/CMBlockBufferCustomBlockSource/init())

[`init(version:AllocateBlock:FreeBlock:refCon:)`](/documentation/CoreMedia/CMBlockBufferCustomBlockSource/init(version:AllocateBlock:FreeBlock:refCon:))

### Properties

[`AllocateBlock`](/documentation/CoreMedia/CMBlockBufferCustomBlockSource/AllocateBlock)

The function to allocate memory.

[`FreeBlock`](/documentation/CoreMedia/CMBlockBufferCustomBlockSource/FreeBlock)

A function to call once when the `CMBlockBuffer` is disposed.

[`refCon`](/documentation/CoreMedia/CMBlockBufferCustomBlockSource/refCon)

Contextual information passed to both the allocate and free function calls.

[`version`](/documentation/CoreMedia/CMBlockBufferCustomBlockSource/version)


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