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package org.graalvm.nativeimage.c.function;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

import org.graalvm.nativeimage.c.CContext;
import org.graalvm.nativeimage.c.constant.CEnum;
import org.graalvm.word.WordBase;

Denotes a native method that calls directly from Java to C, without following the JNI protocol. This means that there are no artificial additional parameters such as the JNI environment passed, and no marshaling or processing of arguments (such as creating handles for objects) is performed. If the method is non-static, the receiver will be ignored. 
 Parameter types and return types must not be Java reference types, only primitive Java types, word types and CEnum types are allowed. The representation of passed primitive values matches exactly how they are specified in the Java language, for example, int as a 32-bit signed integer or char as a 16-bit unsigned integer. boolean is specified as a single byte that corresponds to true if non-zero, and to false if zero. If a Word value is passed that points to a Java object, no guarantees are taken regarding its integrity as a pointer. 
 The class containing the annotated method must be annotated with CContext. 
Since:
19.0/**
 * Denotes a {@code native} method that calls directly from Java to C, without following the JNI
 * protocol. This means that there are no artificial additional parameters such as the JNI
 * environment passed, and no marshaling or processing of arguments (such as creating handles for
 * objects) is performed. If the method is non-static, the receiver will be ignored.
 * <p>
 * Parameter types and return types must not be Java reference types, only
 * {@linkplain Class#isPrimitive() primitive} Java types, {@linkplain WordBase word types} and
 * {@link CEnum} types are allowed. The representation of passed primitive values matches exactly
 * how they are specified in the Java language, for example, {@code int} as a 32-bit signed integer
 * or {@code char} as a 16-bit unsigned integer. {@code boolean} is specified as a single byte that
 * corresponds to {@code true} if non-zero, and to {@code false} if zero. If a Word value is passed
 * that points to a Java object, no guarantees are taken regarding its integrity as a pointer.
 * <p>
 * The class containing the annotated method must be annotated with {@link CContext}.
 *
 * @since 19.0
 */
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface CFunction {

    
Describes the thread state transition performed when the C function is invoked.
Since:
19.0/**
     * Describes the thread state transition performed when the C function is invoked.
     *
     * @since 19.0
     */
    enum Transition {
        
The thread state is transitioned from Java to C, and the Java parts of the stack are made
walkable. The C code can block and call back to Java.
Since:
19.0/**
         * The thread state is transitioned from Java to C, and the Java parts of the stack are made
         * walkable. The C code can block and call back to Java.
         *
         * @since 19.0
         */
        TO_NATIVE,
        
No prologue and epilogue is emitted. The C code must not block and must not call back to
Java. Also, long running C code delays safepoints (and therefore garbage collection) of
other threads until the call returns.
Since:
19.0/**
         * No prologue and epilogue is emitted. The C code must not block and must not call back to
         * Java. Also, long running C code delays safepoints (and therefore garbage collection) of
         * other threads until the call returns.
         *
         * @since 19.0
         */
        NO_TRANSITION,
    }

    
The symbol name to use to link this method. If no value is specified, the name of the method
(without name mangling or a class name prefix) is used.
Since:
19.0/**
     * The symbol name to use to link this method. If no value is specified, the name of the method
     * (without name mangling or a class name prefix) is used.
     *
     * @since 19.0
     */
    String value() default "";

    
The Java-to-C thread transition code used when calling the function.
Since:
19.0/**
     * The Java-to-C thread transition code used when calling the function.
     *
     * @since 19.0
     */
    Transition transition() default Transition.TO_NATIVE;
}