---
title: "CMBufferQueueCallForEachBuffer(_:callback:refcon:)"
framework: coremedia
role: symbol
role_heading: Function
path: "coremedia/cmbufferqueuecallforeachbuffer(_:callback:refcon:)"
---

# CMBufferQueueCallForEachBuffer(_:callback:refcon:)

Calls a function for every buffer in a queue.

## Declaration

```swift
func CMBufferQueueCallForEachBuffer(_ queue: CMBufferQueue, callback: (CMBuffer, UnsafeMutableRawPointer?) -> OSStatus, refcon: UnsafeMutableRawPointer?) -> OSStatus
```

## Parameters

- `queue`: CMBufferQueue that may contain multiple buffers.
- `callback`: Function to be called for each buffer. The callback may modify buffer attachments but should not modify sort-affecting properties (eg, timestamps). The callback should not make other calls to the buffer queue.
- `refcon`: Reference constant supplied to the callback function.

## Return Value

Return Value A result code. See Sample Buffer Error Codes.

## Discussion

Discussion If the callback function returns an error, iteration will stop immediately and the error will be returned.

## See Also

### Managing a Queue

- [CMBufferQueueEnqueue(_:buffer:)](coremedia/cmbufferqueueenqueue(_:buffer:).md)
- [CMBufferQueueDequeue(_:)](coremedia/cmbufferqueuedequeue(_:).md)
- [CMBufferQueueDequeueIfDataReady(_:)](coremedia/cmbufferqueuedequeueifdataready(_:).md)
- [CMBufferQueueMarkEndOfData(_:)](coremedia/cmbufferqueuemarkendofdata(_:).md)
- [CMBufferQueueReset(_:)](coremedia/cmbufferqueuereset(_:).md)
- [CMBufferQueueResetWithCallback(_:callback:refcon:)](coremedia/cmbufferqueueresetwithcallback(_:callback:refcon:).md)
- [CMBufferQueueRemoveTrigger(_:triggerToken:)](coremedia/cmbufferqueueremovetrigger(_:triggertoken:).md)