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# lookupItem(name:in:packer:replyHandler:)

Looks up an item within a directory and maps its disk space.

```
func lookupItem(name: FSFileName, in directory: FSItem, packer: FSExtentPacker, replyHandler reply: @escaping @Sendable (FSItem?, FSFileName?, (any Error)?) -> Void)
```

## Parameters

`name`

The name of the file to look up.

`directory`

The directory in which to look up the file.

`packer`

An extent packer you use to pack the file’s allocated disk space.

`reply`

A block or closure to indicate success or failure. If lookup succeeds, pass the found [`FSItem`](/documentation/FSKit/FSItem) and its [`FSFileName`](/documentation/FSKit/FSFileName), along with a `nil` error. If lookup fails, pass the relevant error as the third parameter; FSKit ignores any [`FSItem`](/documentation/FSKit/FSItem) or [`FSFileName`](/documentation/FSKit/FSFileName) in this case. For an `async` Swift implementation, there’s no reply handler; instead, return a tuple of the [`FSItem`](/documentation/FSKit/FSItem) and its [`FSFileName`](/documentation/FSKit/FSFileName) or throw an error.

## Discussion

This method allows the module to opportunistically supply extents, avoiding future calls to `blockmapFile(_:offset:length:flags:operationID:packer:)`.
Only perform this technique opportunistically.
In particular, don’t perform additional I/O to fetch extent data.

---

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