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Truffle is a multi-language framework for executing dynamic languages
that achieves high performance when combined with Graal.
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package com.oracle.truffle.api.nodes;
import com.oracle.truffle.api.TruffleRuntime;
import com.oracle.truffle.api.frame.VirtualFrame;
/**
* A node that is repeatedly invoked as part of a Truffle loop control structure. Repeating nodes
* must extend {@link Node} or a subclass of {@link Node}.
*
* Repeating nodes are intended to be implemented by guest language implementations. For a full
* usage example please see {@link LoopNode}.
*
* Note: The result of {@link RepeatingNode#shouldContinue shouldContinue}(
* {@link RepeatingNode#executeRepeatingWithValue executeRepeatingWithValue}()) is
* automatically profiled by the loop node, so the {@link RepeatingNode repeating node} should not
* use a loop condition profile.
*
* @see LoopNode
* @see TruffleRuntime#createLoopNode(RepeatingNode)
* @since 0.8 or earlier
*/
public interface RepeatingNode extends NodeInterface {
/**
* A value indicating that the loop should be repeated.
*
* @since 19.3
*/
Object CONTINUE_LOOP_STATUS = new Object() {
@Override
public String toString() {
return "CONTINUE_LOOP_STATUS";
}
};
/**
* A value indicating that the loop should not be repeated. Any other value different than
* {@code CONTINUE_LOOP_STATUS} can also be used to indicate that the loop should not be
* repeated.
*
* @since 19.3
*/
Object BREAK_LOOP_STATUS = new Object() {
@Override
public String toString() {
return "BREAK_LOOP_STATUS";
}
};
/**
* Repeatedly invoked by a {@link LoopNode loop node} implementation until the method returns
* false or throws an exception.
*
* @param frame the current execution frame passed through the interpreter
* @return true if the method should be executed again to complete the loop and
* false if it must not.
* @since 0.8 or earlier
*/
boolean executeRepeating(VirtualFrame frame);
/**
* Repeatedly invoked by a {@link LoopNode loop node} implementation, but allows returning a
* language-specific loop exit status. Only languages that need to return custom loop statuses
* should override this method.
*
* @param frame the current execution frame passed through the interpreter
* @return a value v satisfying {@link RepeatingNode#shouldContinue
* shouldContinue(v)} == true if the method should be executed again to
* complete the loop and any other value if it must not.
* @since 19.3
*/
default Object executeRepeatingWithValue(VirtualFrame frame) {
if (executeRepeating(frame)) {
return CONTINUE_LOOP_STATUS;
} else {
return BREAK_LOOP_STATUS;
}
}
/**
* Returns a placeholder loop status used internally before the first iteration.
*
* @return a value satisfying
* {@link RepeatingNode#shouldContinue shouldContinue}({@link RepeatingNode#initialLoopStatus initialLoopStatus}(v)) == true
* @since 20.3
*/
default Object initialLoopStatus() {
return CONTINUE_LOOP_STATUS;
}
/**
* Predicate called on values returned by
* {@link RepeatingNode#executeRepeatingWithValue(VirtualFrame) executeRepeatingWithValue()}.
*
* @param returnValue a value returned by
* {@link RepeatingNode#executeRepeatingWithValue(VirtualFrame)
* executeRepeatingWithValue()}
* @return true if the loop should continue executing or false otherwise
* @since 20.3
*/
default boolean shouldContinue(Object returnValue) {
return returnValue == initialLoopStatus();
}
}