---
title: copyPhysicalExtent
framework: kernel
role: pseudoSymbol
path: kernel/iostorage/1810820-copyphysicalextent
---

# copyPhysicalExtent

## Declaration

```occ
virtual IOStorage * copyPhysicalExtent(
 IOService *client, 
 UInt64 *byteStart, 
 UInt64 *byteCount); 
```

## Parameters

- `client`: Client requesting the operation.
- `byteStart`: Starting byte offset for the operation. Returns a physical byte offset, relative to the physical storage object, on success.
- `byteCount`: Size of the operation. Returns the actual number of bytes which can be transferred, relative to the physical storage object, on success.

## Return Value

Return Value A reference to the physical storage object, which should be released by the caller, or a null on error.

## Overview

Overview Convert the specified byte offset into a physical byte offset, relative to a physical storage object. This call should only be made within the context of lockPhysicalExtents().

## See Also

### Miscellaneous

- [complete](kernel/iostorage/1810767-complete.md)
- [handleClose](kernel/iostorage/1810866-handleclose.md)
- [handleIsOpen](kernel/iostorage/1810905-handleisopen.md)
- [handleOpen](kernel/iostorage/1810948-handleopen.md)
- [lockPhysicalExtents](kernel/iostorage/1810985-lockphysicalextents.md)
- [open](kernel/iostorage/1811013-open.md)
- [read()](kernel/iostorage/1811038-read.md)
- [read()](kernel/iostorage/1811068-read.md)
- [synchronizeCache](kernel/iostorage/1811091-synchronizecache.md)
- [unlockPhysicalExtents](kernel/iostorage/1811117-unlockphysicalextents.md)
- [unmap](kernel/iostorage/1811145-unmap.md)
- [write()](kernel/iostorage/1811168-write.md)
- [write()](kernel/iostorage/1811185-write.md)