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# FSExtentPacker

A type that directs the kernel to map space on disk to a specific file managed by this file system.

```
class FSExtentPacker
```

## Overview

*Extents* provide the kernel the logical-to-physical mapping of a given file.
An extent describes a physical offset on disk, and a length and a logical offset within the file.
Rather than working with extents directly, you use this type’s methods to provide or “pack” extent information, which FSKit then passes to the kernel.

## Topics

### Packing extents

[`packExtent(resource:type:logicalOffset:physicalOffset:length:)`](/documentation/FSKit/FSExtentPacker/packExtent(resource:type:logicalOffset:physicalOffset:length:))

Packs a single extent to send to the kernel.

[`FSExtentType`](/documentation/FSKit/FSExtentType)

An enumeration of types of extents.


---

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