OFFSETOF

• Source: https://www.freebasic.net/wiki/wikka.php?wakka=KeyPgOffsetof
• Last revised: 2016-03-13

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Returns the offset of a field within a type.

Syntax

` #define Offsetof(typename, fieldname) cint( @cast( typename ptr, 0 )->fieldname )

`

Usage

` result = Offsetof( typename, fieldname )

`

Parameters

typename

Name of the type as defined using the Type...End Type statements.

fieldname

Name of the field as defined within the type (or within the base types for a derived type).

Description

For a non-derived type, Offsetof will return the location fieldname as offset in bytes from the beginning of typename.

For a derived type, Offsetof will return the location fieldname as offset in bytes from the beginning of its highest base type.

Note: if a member of the base type is overridden by a new member, the offset of the old member cannot be accessed from the derived type.

Examples

start GeSHi

Type MyType
  x As Single
  y As Single
  Union
    b As Byte
    i As Integer
  End Union
End Type

Print "OffsetOf x = "; OffsetOf(MyType, x)
Print "OffsetOf y = "; OffsetOf(MyType, y)
Print "OffsetOf b = "; OffsetOf(MyType, b)
Print "OffsetOf i = "; OffsetOf(MyType, i)

end GeSHi

Output

OffsetOf x =  0
OffsetOf y =  4
OffsetOf b =  8
OffsetOf i =  8

Dialect Differences

• Not available in the -lang qb dialect unless referenced with the alias __Offsetof.

Differences from QB

• New to FreeBASIC

See also

• Type...End Type
• Sizeof

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