---
title: SegmentFunction
framework: kernel
role: pseudoSymbol
path: kernel/iodmacommand/segmentfunction
---

# SegmentFunction

A C function that translates a 64-bit segment and outputs a single desired segment to the specified array.

## Declaration

```occ
typedef bool ( *SegmentFunction)(
   IODMACommand *target,
   Segment64 segment,
   void *segments,
   UInt32 segmentIndex);
```

## Parameters

- `segment`: The 64Bit I/O bus address and length.
- `segments`: Base of the output vector of DMA address length pairs.
- `segmentIndex`: Index to output 'segment' in the 'segments' array.

## Return Value

Return Value Returns true if segment encoding succeeded. false may be returned if the current segment does not fit in an output segment, i.e. a 38bit address wont fit into a 32 encoding.

## Overview

Overview There are a group of pre-implemented SegmentFunctions that may be usefull to the developer below.