content: /*******************************************************************************
  * Copyright (c) 2012 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.lib;
  
  import org.luaj.vm2.LuaTable;
  import org.luaj.vm2.LuaValue;
  import org.luaj.vm2.Varargs;
  
  /**
   * Subclass of LibFunction that implements the Lua standard {@code bit32} library.
   * <p> 
   * Typically, this library is included as part of a call to either 
   * {@link JsePlatform#standardGlobals()} or {@link JmePlatform#standardGlobals()}
   * <pre> {@code
   * Globals globals = JsePlatform.standardGlobals();
   * System.out.println( globals.get("bit32").get("bnot").call( LuaValue.valueOf(2) ) );
   * } </pre>
   * <p>
   * To instantiate and use it directly, 
   * link it into your globals table via {@link LuaValue#load(LuaValue)} using code such as:
   * <pre> {@code
   * Globals globals = new Globals();
   * globals.load(new JseBaseLib());
   * globals.load(new PackageLib());
   * globals.load(new Bit32Lib());
   * System.out.println( globals.get("bit32").get("bnot").call( LuaValue.valueOf(2) ) );
   * } </pre>
   * <p>
   * This has been implemented to match as closely as possible the behavior in the corresponding library in C.
   * @see LibFunction
   * @see JsePlatform
   * @see JmePlatform
   * @see <a href="http://www.lua.org/manual/5.2/manual.html#6.7">Lua 5.2 Bitwise Operation Lib Reference</a>
   */
  public class Bit32Lib extends TwoArgFunction {
  
  	public Bit32Lib() {
  	}
  
  	public LuaValue call(LuaValue modname, LuaValue env) {
  		LuaTable t = new LuaTable();
  		bind(t, Bit32LibV.class, new String[] {
  			"band", "bnot", "bor", "btest", "bxor", "extract", "replace"
  		});
  		bind(t, Bit32Lib2.class, new String[] {
  			"arshift", "lrotate", "lshift", "rrotate", "rshift"
  		});
  		env.set("bit32", t);
  		env.get("package").get("loaded").set("bit32", t);
  		return t;
  	}
  
  	static final class Bit32LibV extends VarArgFunction {
  		public Varargs invoke(Varargs args) {
  			switch ( opcode ) {
  			case 0: return Bit32Lib.band( args );
  			case 1: return Bit32Lib.bnot( args );
  			case 2: return Bit32Lib.bor( args );
  			case 3: return Bit32Lib.btest( args );
  			case 4: return Bit32Lib.bxor( args );
  			case 5:
  				return Bit32Lib.extract( args.checkint(1), args.checkint(2), args.optint(3, 1) );
  			case 6:
  				return Bit32Lib.replace( args.checkint(1), args.checkint(2),
  						args.checkint(3), args.optint(4, 1) );
  			}
  			return NIL;
  		}
  	}
  
  	static final class Bit32Lib2 extends TwoArgFunction {
  
  		public LuaValue call(LuaValue arg1, LuaValue arg2) {
  			switch ( opcode ) {
  			case 0: return Bit32Lib.arshift(arg1.checkint(), arg2.checkint());
  			case 1: return Bit32Lib.lrotate(arg1.checkint(), arg2.checkint());
  			case 2: return Bit32Lib.lshift(arg1.checkint(), arg2.checkint());
  			case 3: return Bit32Lib.rrotate(arg1.checkint(), arg2.checkint());
  			case 4: return Bit32Lib.rshift(arg1.checkint(), arg2.checkint());
  			}
  			return NIL;
  		}
  		
  	}
  
  	static LuaValue arshift(int x, int disp) {
  		if (disp >= 0) {
  			return bitsToValue(x >> disp);
  		} else {
  			return bitsToValue(x << -disp);
  		}
  	}
  
  	static LuaValue rshift(int x, int disp) {
  		if (disp >= 32 || disp <= -32) {
  			return ZERO;
  		} else if (disp >= 0) {
  			return bitsToValue(x >>> disp);
  		} else {
  			return bitsToValue(x << -disp);
  		}
  	}
  
  	static LuaValue lshift(int x, int disp) {
  		if (disp >= 32 || disp <= -32) {
  			return ZERO;
  		} else if (disp >= 0) {
  			return bitsToValue(x << disp);
  		} else {
  			return bitsToValue(x >>> -disp);
  		}
  	}
  
  	static Varargs band( Varargs args ) {
  		int result = -1;
  		for ( int i = 1; i <= args.narg(); i++ ) {
  			result &= args.checkint(i);
  		}
  		return bitsToValue( result );
  	}
  
  	static Varargs bnot( Varargs args ) {
  		return bitsToValue( ~args.checkint(1) );
  	}
  
  	static Varargs bor( Varargs args ) {
  		int result = 0;
  		for ( int i = 1; i <= args.narg(); i++ ) {
  			result |= args.checkint(i);
  		}
  		return bitsToValue( result );
  	}
  
  	static Varargs btest( Varargs args ) {
  		int bits = -1;
  		for ( int i = 1; i <= args.narg(); i++ ) {
  			bits &= args.checkint(i);
  		}
  		return valueOf( bits != 0 );
  	}
  
  	static Varargs bxor( Varargs args ) {
  		int result = 0;
  		for ( int i = 1; i <= args.narg(); i++ ) {
  			result ^= args.checkint(i);
  		}
  		return bitsToValue( result );
  	}
  
  	static LuaValue lrotate(int x, int disp) {
  		if (disp < 0) {
  			return rrotate(x, -disp);
  		} else {
  			disp = disp & 31;
  			return bitsToValue((x << disp) | (x >>> (32 - disp)));
  		}
  	}
  
  	static LuaValue rrotate(int x, int disp) {
  		if (disp < 0) {
  			return lrotate(x, -disp);
  		} else {
  			disp = disp & 31;
  			return bitsToValue((x >>> disp) | (x << (32 - disp)));
  		}
  	}
  
  	static LuaValue extract(int n, int field, int width) {
  		if (field < 0) {
  			argerror(2, "field cannot be negative");
  		}
  		if (width < 0) {
  			argerror(3, "width must be postive");
  		}
  		if (field + width > 32) {
  			error("trying to access non-existent bits");
  		}
  		return bitsToValue((n >>> field) & (-1 >>> (32 - width)));
  	}
  
  	static LuaValue replace(int n, int v, int field, int width) {
  		if (field < 0) {
  			argerror(3, "field cannot be negative");
  		}
  		if (width < 0) {
  			argerror(4, "width must be postive");
  		}
  		if (field + width > 32) {
  			error("trying to access non-existent bits");
  		}
  		int mask = (-1 >>> (32 - width)) << field;
  		n = (n & ~mask) | ((v << field) & mask);
  		return bitsToValue(n);
  	}
  
  	private static LuaValue bitsToValue( int x ) {
  		return ( x < 0 ) ? valueOf((double) ((long) x & 0xFFFFFFFFL)) : valueOf(x); 
  	}
  }
  