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package org.luaj.vm2;
import org.luaj.vm2.Varargs.ArrayPartVarargs;
import org.luaj.vm2.Varargs.PairVarargs;
/**
* Subclass of {@link Varargs} that represents a lua tail call
* in a Java library function execution environment.
*
* Since Java doesn't have direct support for tail calls,
* any lua function whose {@link Prototype} contains the
* {@link Lua#OP_TAILCALL} bytecode needs a mechanism
* for tail calls when converting lua-bytecode to java-bytecode.
*
* The tail call holds the next function and arguments,
* and the client a call to {@link #eval()} executes the function
* repeatedly until the tail calls are completed.
*
* Normally, users of luaj need not concern themselves with the
* details of this mechanism, as it is built into the core
* execution framework.
* @see Prototype
* @see LuaJC
*/
public class TailcallVarargs extends Varargs {
private LuaValue func;
private Varargs args;
private Varargs result;
public TailcallVarargs(LuaValue f, Varargs args) {
this.func = f;
this.args = args;
}
public TailcallVarargs(LuaValue object, LuaValue methodname, Varargs args) {
this.func = object.get(methodname);
this.args = LuaValue.varargsOf(object, args);
}
public boolean isTailcall() {
return true;
}
public Varargs eval() {
while ( result == null ) {
Varargs r = func.onInvoke(args);
if (r.isTailcall()) {
TailcallVarargs t = (TailcallVarargs) r;
func = t.func;
args = t.args;
}
else {
result = r;
func = null;
args = null;
}
}
return result;
}
public LuaValue arg( int i ) {
if ( result == null )
eval();
return result.arg(i);
}
public LuaValue arg1() {
if (result == null)
eval();
return result.arg1();
}
public int narg() {
if (result == null)
eval();
return result.narg();
}
public Varargs subargs(int start) {
if (result == null)
eval();
return result.subargs(start);
}
}