org.luaj.vm2.TailcallVarargs Maven / Gradle / Ivy
Show all versions of luaj-jse Show documentation
/*******************************************************************************
* Copyright (c) 2010-2011 Luaj.org. All rights reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
******************************************************************************/
package org.luaj.vm2;
/**
* 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 org.luaj.vm2.luajc.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);
}
}