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JNA API> 3.0.4 | ||||||||
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java.lang.Objectcom.sun.jna.Structure
com.sun.jna.Union
public abstract class Union
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 |
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Nested classes/interfaces inherited from class com.sun.jna.Structure |
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Structure.ByReference, Structure.ByValue, Structure.StructField |
Field Summary |
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Fields inherited from class com.sun.jna.Structure |
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ALIGN_DEFAULT, ALIGN_GNUC, ALIGN_MSVC, ALIGN_NONE, CALCULATE_SIZE, isPPC, isSPARC |
Constructor Summary | |
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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 | |
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(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 |
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allocateMemory, allocateMemory, calculateAlignedSize, clear, ensureAllocated, 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 |
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clone, finalize, getClass, notify, notifyAll, wait, wait, wait |
Constructor Detail |
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protected Union()
protected Union(int size)
protected Union(int size, int alignType)
Method Detail |
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public void setType(java.lang.Class type)
java.lang.IllegalArgumentException
- if the type does not correspond to
any declared union field.void writeField(Structure.StructField field)
writeField
in class Structure
java.lang.Object readField(Structure.StructField field)
readField
in class Structure
int calculateSize(boolean force)
calculateSize
in class Structure
protected int getNativeAlignment(java.lang.Class type, java.lang.Object value, boolean isFirstElement)
getNativeAlignment
in class Structure
Pointer getTypeInfo()
getTypeInfo
in class Structure
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