com.sun.jna

Class Union

java.lang.Object

com.sun.jna.Structure

com.sun.jna.Union

Direct Known Subclasses:

NTSecApi.LSA_FOREST_TRUST_RECORD.UNION, OaIdl.BINDPTR, OaIdl.CURRENCY, OaIdl.DECIMAL._DECIMAL1, OaIdl.DECIMAL._DECIMAL2, OaIdl.ELEMDESC._ELEMDESC, OaIdl.TYPEDESC._TYPEDESC, OaIdl.VARDESC._VARDESC, Variant.VARIANT, Variant.VARIANT._VARIANT.__VARIANT, WinBase.SYSTEM_INFO.UNION, WinNT.LARGE_INTEGER.UNION, WinNT.SYSTEM_LOGICAL_PROCESSOR_INFORMATION.AnonymousUnionPayload, WinRas.RASTUNNELENDPOINT.UNION, WinUser.INPUT.INPUT_UNION, X11.XClientMessageEvent.Data, X11.XEvent

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.FFIType, Structure.StructField, Structure.StructureSet

Field Summary

Fields inherited from class com.sun.jna.Structure

ALIGN_DEFAULT, ALIGN_GNUC, ALIGN_MSVC, ALIGN_NONE, CALCULATE_SIZE, fieldOrder, layoutInfo

Constructor Summary

Constructors

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

Method Summary

Modifier and Type	Method and Description
protected List	getFieldOrder() Unions do not need a field order, so automatically provide a value to satisfy checking in the Structure superclass.
protected int	getNativeAlignment(Class type, Object value, boolean isFirstElement) All fields are considered the "first" element.
Object	getTypedValue(Class type) Reads the Structure field of the given type from memory, sets it as the active type and returns it.
Object	readField(String fieldName) Force a read of the given field from native memory.
protected Object	readField(Structure.StructField field) Avoid reading pointer-based fields and structures unless explicitly selected.
void	setType(Class type) Indicates by type which field will be used to write to native memory.
void	setType(String fieldName) Indicates which field will be used to write to native memory.
Object	setTypedValue(Object object) Set the active type and its value.
void	writeField(String fieldName) Write the given field value to native memory.
void	writeField(String fieldName, Object value) Write the given field value to the field and native memory.
protected void	writeField(Structure.StructField field) Only the currently selected field will be written.

Methods inherited from class com.sun.jna.Structure

allocateMemory, allocateMemory, autoAllocate, autoRead, autoRead, autoWrite, autoWrite, busy, cacheTypeInfo, calculateSize, calculateSize, clear, conditionalAutoRead, dataEquals, dataEquals, ensureAllocated, equals, fieldOffset, fields, getAutoRead, getAutoWrite, getFieldList, getFields, getFieldTypeInfo, getFieldValue, getNativeSize, getNativeSize, getPointer, getStringEncoding, getStructAlignment, getTypeInfo, getTypeInfo, getTypeMapper, hashCode, newInstance, newInstance, read, reading, setAlignType, setAutoRead, setAutoSynch, setAutoWrite, setFieldOrder, setFieldValue, setStringEncoding, size, size, size, sortFields, toArray, toArray, toString, toString, typeInfoField, updateStructureByReference, useMemory, useMemory, useMemory, validate, write

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(Pointer p)

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

Union

protected Union(Pointer p,
                int alignType)

Create a Union of the given size and alignment type.

Union

protected Union(TypeMapper mapper)

Create a Union of the given size and alignment type.

Union

protected Union(Pointer p,
                int alignType,
                TypeMapper mapper)

Create a Union of the given size and alignment type.

Method Detail

getFieldOrder

protected List getFieldOrder()

Unions do not need a field order, so automatically provide a value to satisfy checking in the Structure superclass.

Specified by:

getFieldOrder in class Structure

Returns:

ordered list of field names

setType

public void setType(Class type)

Indicates by type which field will be used to write to native memory. If there are multiple fields of the same type, use setType(String) instead with the field name.

Parameters:

type - desired active type for the union

Throws:

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

setType

public void setType(String fieldName)

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

Parameters:

fieldName - desired field to use for the active union type

Throws:

IllegalArgumentException - if the name does not correspond to any declared union field.

readField

public Object readField(String fieldName)

Force a read of the given field from native memory.

Overrides:

readField in class Structure

Parameters:

fieldName - field to be read

Returns:

the new field value, after updating

Throws:

IllegalArgumentException - if no field exists with the given name

writeField

public void writeField(String fieldName)

Write the given field value to native memory. The given field will become the active one.

Overrides:

writeField in class Structure

Parameters:

fieldName - which field to synch

Throws:

IllegalArgumentException - if no field exists with the given name

writeField

public void writeField(String fieldName,
                       Object value)

Write the given field value to the field and native memory. The given field will become the active one.

Overrides:

writeField in class Structure

Parameters:

fieldName - field to write

value - value to write

Throws:

IllegalArgumentException - if no field exists with the given name

getTypedValue

public Object getTypedValue(Class type)

Reads the Structure field of the given type from memory, sets it as the active type and returns it. Convenience method for

 Union u;
 Class type;
 u.setType(type);
 u.read();
 value = u.field;
 

Parameters:

type - class type of the Structure field to read

Returns:

the Structure field with the given type

setTypedValue

public Object setTypedValue(Object object)

Set the active type and its value. Convenience method for

 Union u;
 Class type;
 u.setType(type);
 u.field = value;
 

Parameters:

object - instance of a class which is part of the union

Returns:

this Union object

writeField

protected void writeField(Structure.StructField field)

Only the currently selected field will be written.

Overrides:

writeField in class Structure

Parameters:

field - internal field representation to synch to native memory

readField

protected 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

Parameters:

field - field to be read

Returns:

value of the requested field

getNativeAlignment

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

All fields are considered the "first" element.

Overrides:

getNativeAlignment in class Structure

Parameters:

type - field type

value - field value, if available

isFirstElement - is this field the first element in the struct?

Returns:

the native byte alignment