com.sun.jna

Class Union

java.lang.Object

com.sun.jna.Structure

com.sun.jna.Union

public abstract class Union
extends Structure

Represents a native union. When writing to native memory, the field corresponding to the type passed to setType(java.lang.Class) will be written to native memory. Upon reading from native memory, Structure, String, or WString fields will not be initialized unless they are the current field as identified by a call to setType(java.lang.Class). The current field is always unset by default to avoid accidentally attempting to read a field that is not valid. In the case of a String, for instance, an invalid pointer may result in a memory fault when attempting to initialize the String.

Nested Class Summary

Nested classes/interfaces inherited from class com.sun.jna.Structure

Structure.ByReference, Structure.ByValue, Structure.StructField

Field Summary

Fields inherited from class com.sun.jna.Structure

ALIGN_DEFAULT, ALIGN_GNUC, ALIGN_MSVC, ALIGN_NONE, CALCULATE_SIZE, isPPC, isSPARC

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	Union() Create a Union whose size and alignment will be calculated automatically.
protected	Union(int size) Create a Union of the given size, using default alignment.
protected	Union(int size, int alignType) Create a Union of the given size and alignment type.

Method Summary

Methods

Modifier and Type	Method and Description
(package private) int	calculateSize(boolean force) Adjust the size to be the size of the largest element, and ensure all fields begin at offset zero.
protected int	getNativeAlignment(java.lang.Class type, java.lang.Object value, boolean isFirstElement) All fields are considered the "first" element.
(package private) Pointer	getTypeInfo() Return type information for the largest field.
(package private) java.lang.Object	readField(Structure.StructField field) Avoid reading pointer-based fields and structures unless explicitly selected.
void	setType(java.lang.Class type) Indicates which field will be used to write to native memory.
(package private) void	writeField(Structure.StructField field) Only the currently selected field will be written.

Methods inherited from class com.sun.jna.Structure

allocateMemory, allocateMemory, calculateAlignedSize, clear, equals, fields, getField, getPointer, getStructAlignment, getTypeInfo, hashCode, newInstance, read, readField, setAlignType, setTypeMapper, size, toArray, toArray, toString, updateStructureByReference, useMemory, useMemory, write, writeField

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

Union

protected Union()

Create a Union whose size and alignment will be calculated automatically.

Union

protected Union(int size)

Create a Union of the given size, using default alignment.

Union

protected Union(int size,
     int alignType)

Create a Union of the given size and alignment type.

Method Detail

setType

public void setType(java.lang.Class type)

Indicates which field will be used to write to native memory.

Throws:

java.lang.IllegalArgumentException - if the type does not correspond to any declared union field.

writeField

void writeField(Structure.StructField field)

Only the currently selected field will be written.

Overrides:

writeField in class Structure

readField

java.lang.Object readField(Structure.StructField field)

Avoid reading pointer-based fields and structures unless explicitly selected. Structures may contain pointer-based fields which can crash the VM if not properly initialized.

Overrides:

readField in class Structure

calculateSize

int calculateSize(boolean force)

Adjust the size to be the size of the largest element, and ensure all fields begin at offset zero.

Overrides:

calculateSize in class Structure

getNativeAlignment

protected int getNativeAlignment(java.lang.Class type,
                     java.lang.Object value,
                     boolean isFirstElement)

All fields are considered the "first" element.

Overrides:

getNativeAlignment in class Structure

getTypeInfo

Pointer getTypeInfo()

Return type information for the largest field.

Overrides:

getTypeInfo in class Structure