---
name: "VistaIOOffset"
section: "3"
platform: "linux"
package: "libvistaio-dev"
version: "1.2.19-3+b2"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/VistaIOOffset"
---

# VistaIOOffset(3)

determine the byte offset of a structure field

## NAME

VistaIOOffset, VistaIOOffsetOf - determine the byte offset of a structure field

## SYNTAX

```
#include <vistaio.h>
```

**size\_t VistaIOOffset (***pointer\_type***,** *field\_name***)**

**Type** *pointer\_type***;** **Field** *field\_name***;**

**size\_t VistaIOOffsetOf (***struct\_type***,** *field\_name***)**

**Type** *struct\_type***;** **Field** *field\_name***;**

## ARGUMENTS

- *field\_name*

  **Specifies the name of a structure field for which to calculate the byte** **offset.**

- *pointer\_type*

  **Specifies a type that is declared as a pointer to a structure.**

- *struct\_type*

  **Specifies a type that is declared as a structure.**

## DESCRIPTION

**The VistaIOOffset and VistaIOOffsetOf macros return the byte offset of the** *field\_name* **field within its structure.**

## SEE ALSO

## NOTES

**These are equivalent to the X Toolkit macros XtOffset(3Xt) and** **XtOffsetOf(3Xt). ANSI C defines an offsetof macro, which is to** **be preferred over any of these.**