graal/21.0.0.2 : sdk/org.graalvm.nativeimage/org/graalvm/nativeimage/c/struct/CBitfield.java

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 * person obtaining a copy of this software, associated documentation and/or
 * data (collectively the "Software"), free of charge and under any and all
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 * unmodified Software as contributed to or provided by such licensor, or (ii)
 * the Larger Works (as defined below), to deal in both
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 * (a) the Software, and
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 * (b) any piece of software and/or hardware listed in the lrgrwrks.txt file if
 * one is included with the Software each a "Larger Work" to which the Software
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 * Software and the Larger Work(s), and to sublicense the foregoing rights on
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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 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 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 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 FieldType must be must be a primitive integer type or a word type. 
 The optional parameter locationIdentity specifies the LocationIdentity to be used for the memory access. Two memory accesses with two different location identities are guaranteed to not alias. Note that 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/**
 * Denotes a method as a bitfield access of a {@link CStruct C struct}.
 * <p>
 * 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]);}
 * <p>
 * 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.
 * <p>
 * The receiver is the pointer to the struct that is accessed, i.e., the base address of the memory
 * access.
 * <p>
 * The {@code FieldType} must be must be a primitive integer type or a {@link WordBase word type}.
 * <p>
 * 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.
 * <p>
 * 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 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/**
     * 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 "";
}
/

graal/ 21.0.0.2/ sdk/org.graalvm.nativeimage/org/graalvm/nativeimage/c/struct/CBitfield.java
