JNA API 3.2.4

com.sun.jna

Class Union

  • Direct Known Subclasses:
    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.
    • 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

      • 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.
      • readField

        public java.lang.Object readField(java.lang.String name)
        Force a read of the given field from native memory.
        Overrides:
        readField in class Structure
        Returns:
        the new field value, after updating
        Throws:
        java.lang.IllegalArgumentException - if no field exists with the given name
      • writeField

        public void writeField(java.lang.String name)
        Write the given field value to native memory. The given field will become the active one.
        Overrides:
        writeField in class Structure
        Throws:
        java.lang.IllegalArgumentException - if no field exists with the given name
      • writeField

        public void writeField(java.lang.String name,
                      java.lang.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
        Throws:
        java.lang.IllegalArgumentException - if no field exists with the given name
      • getTypedValue

        public java.lang.Object getTypedValue(java.lang.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 java.lang.Object setTypedValue(java.lang.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
      • 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()
        Avoid calculating type information until we know our biggest field. Return type information for the largest field to ensure all available bits are used.
        Overrides:
        getTypeInfo in class Structure
JNA API 3.2.4

Copyright © 2007-2009 Timothy Wall. All Rights Reserved.