org.graalvm.nativeimage.c.struct.CBitfield Maven / Gradle / Ivy
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* (a) the Software, and
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package org.graalvm.nativeimage.c.struct;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import org.graalvm.word.LocationIdentity;
import org.graalvm.word.WordBase;
/**
* Denotes a method as a bitfield access of a {@link CStruct C struct}.
*
* If the method has a non-void return type, it is a get-method of the field. Calls of the method
* are replaced with a memory read. The possible signatures are
* {@code FieldType getFieldName([LocationIdentity locationIdentity]);}
*
* If the method has the return type void, it is a set-method of the field. Calls of the method are
* replaced with memory accesses. The possible signatures are
* {@code void setFieldName(FieldType value, [LocationIdentity locationIdentity]);} Most
* architectures do not provide write instructions on the bit-level. Therefore, the memory write of
* the new value is preceded by a memory read of the old value. This makes bitfield writes
* non-atomic.
*
* The receiver is the pointer to the struct that is accessed, i.e., the base address of the memory
* access.
*
* The {@code FieldType} must be must be a primitive integer type or a {@link WordBase word type}.
*
* The optional parameter {@code locationIdentity} specifies the {@link LocationIdentity} to be used
* for the memory access. Two memory accesses with two different location identities are guaranteed
* to not alias. Note that {@link UniqueLocationIdentity} annotation, cannot be used on bitfields.
*
* Multiple accessor methods, with different signatures according to the rules of allowed
* signatures, are allowed for a single field.
*
* @since 19.0
*/
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.METHOD})
public @interface CBitfield {
/**
* Specifies the field name inside the {@link CStruct C struct}. If no name is provided, the
* method name is used as the field name. A possible "get" or "set" prefix of the method name is
* removed.
*
* @since 19.0
*/
String value() default "";
}