Improve __concat metatag

src/core/org/luaj/vm2/Buffer.java

@@ -104,6 +104,18 @@ public final class Buffer {
 		return this;
 	}
 
+	public Buffer concatTo(LuaValue lhs) {
+		return setvalue(lhs.concat(value()));
+	}
+
+	public Buffer concatTo(LuaString lhs) {
+		return value!=null? setvalue(lhs.concat(value)): prepend(lhs);
+	}
+
+	public Buffer concatTo(LuaNumber lhs) {
+		return value!=null? setvalue(lhs.concat(value)): prepend(lhs.strvalue());
+	}
+
 	public Buffer prepend(LuaString s) {
 		int n = s.m_length;
 		makeroom( n, 0 );

src/core/org/luaj/vm2/LuaNumber.java

@@ -63,7 +63,7 @@ public class LuaNumber extends LuaValue {
 	}
 
 	public LuaValue concat(LuaValue rhs)      { return rhs.concatTo(this); }
-	public Buffer   concat(Buffer rhs)        { return concat(rhs.value()).buffer(); }
+	public Buffer   concat(Buffer rhs)        { return rhs.concatTo(this); }
 	public LuaValue concatTo(LuaNumber lhs)   { return strvalue().concatTo(lhs.strvalue()); }
 	public LuaValue concatTo(LuaString lhs)   { return strvalue().concatTo(lhs); }
 

src/core/org/luaj/vm2/LuaString.java

@@ -156,7 +156,7 @@ public class LuaString extends LuaValue {
 
 	// concatenation
 	public LuaValue concat(LuaValue rhs)      { return rhs.concatTo(this); }
-	public Buffer   concat(Buffer rhs)        { return rhs.prepend(this); }
+	public Buffer   concat(Buffer rhs)        { return rhs.concatTo(this); }
 	public LuaValue concatTo(LuaNumber lhs)   { return concatTo(lhs.strvalue()); }
 	public LuaValue concatTo(LuaString lhs)   { 
 		byte[] b = new byte[lhs.m_length+this.m_length];

src/core/org/luaj/vm2/LuaValue.java

@@ -350,7 +350,7 @@ public class LuaValue extends Varargs {
 	public LuaValue concatTo(LuaNumber lhs)   { return lhs.concatmt(this); }
 	public LuaValue concatTo(LuaString lhs)   { return lhs.concatmt(this); }
 	public Buffer   buffer()                  { return new Buffer(this); }
-	public Buffer   concat(Buffer rhs)        { return rhs.setvalue(concat(rhs.value())); }
+	public Buffer   concat(Buffer rhs)        { return rhs.concatTo(this); }
 	public LuaValue concatmt(LuaValue rhs) {
 		LuaValue h=metatag(CONCAT);
 		if ( h.isnil() && (h=rhs.metatag(CONCAT)).isnil())

src/jse/org/luaj/vm2/lua2java/JavaCodeGen.java

@@ -583,14 +583,19 @@ public class JavaCodeGen {
 			case Lua.OP_NEQ: out(evalLuaValue(exp.lhs)+".neq("+evalLuaValue(exp.rhs)+")"); return;
 			case Lua.OP_CONCAT: 
 				if ( isConcatExp(exp.rhs) ) {
-					out( "new Buffer().append("+evalLuaValue(exp.lhs)+")" );
+					out( evalLuaValue(exp.lhs) );
 					Exp e = exp.rhs;
-					for ( ; isConcatExp(e); e=((BinopExp)e).rhs ) 
+					String close = "";
-						out( ".append("+evalLuaValue(((BinopExp)e).lhs)+")" );
+					for ( ; isConcatExp(e); e=((BinopExp)e).rhs ) { 
-					out( ".append("+evalLuaValue(e)+")" );
+						out( ".concat("+evalLuaValue(((BinopExp)e).lhs) );
-					out( ".tostring()" );
+						close += ')';
-				} else
+					}
+					out( ".concat("+evalLuaValue(e)+".buffer())" );
+					out( close );
+					out( ".value()" );
+				} else {
 					out(evalLuaValue(exp.lhs)+".concat("+evalLuaValue(exp.rhs)+")");
+				}
 				return;
 			default: throw new IllegalStateException("unknown bin op:"+exp.op);
 			}

src/jse/org/luaj/vm2/luajc/JavaBuilder.java

@@ -109,7 +109,6 @@ public class JavaBuilder {
 	private static final Type[] ARG_TYPES_STRING = { Type.STRING };
 	private static final Type[] ARG_TYPES_CHARARRAY = { TYPE_CHARARRAY };
 	private static final Type[] ARG_TYPES_VARARGS_INT =  { TYPE_VARARGS, Type.INT };	
-	private static final Type[] ARG_TYPES_LUASTRING = { TYPE_LUASTRING };
 	private static final Type[] ARG_TYPES_INT_LUAVALUE = { Type.INT, TYPE_LUAVALUE };
 	private static final Type[] ARG_TYPES_INT_VARARGS = { Type.INT, TYPE_VARARGS };
 	private static final Type[] ARG_TYPES_LUAVALUE_VARARGS = { TYPE_LUAVALUE, TYPE_VARARGS };
@@ -121,6 +120,7 @@ public class JavaBuilder {
 	private static final Type[] ARG_TYPES_LUAVALUE_LUAVALUE = { TYPE_LUAVALUE, TYPE_LUAVALUE };
 	private static final Type[] ARG_TYPES_INT_INT = { Type.INT, Type.INT };
 	private static final Type[] ARG_TYPES_LUAVALUE = { TYPE_LUAVALUE };
+	private static final Type[] ARG_TYPES_BUFFER = { TYPE_BUFFER };
 
 	// names, arg types for main prototype classes
 	private static final String[]     SUPER_NAME_N   = { STR_FUNC0, STR_FUNC1, STR_FUNC2, STR_FUNC3, STR_FUNCV, };
@@ -773,14 +773,19 @@ public class JavaBuilder {
 		append(factory.createInvoke(STR_LUAVALUE, "rawsetlist", Type.VOID, ARG_TYPES_INT_VARARGS, Constants.INVOKEVIRTUAL));
 	}
 
-	public void newBuffer() {
+	public void concatvalue() {
-		append(factory.createNew(TYPE_BUFFER));
+        append(factory.createInvoke(STR_LUAVALUE, "concat", TYPE_LUAVALUE, ARG_TYPES_LUAVALUE, Constants.INVOKEVIRTUAL));
-		append(InstructionConstants.DUP);
-		append(factory.createInvoke(STR_BUFFER, "<init>", Type.VOID, Type.NO_ARGS, Constants.INVOKESPECIAL));
 	}
 	
-	public void appendBuffer() {
+	public void concatbuffer() {
-        append(factory.createInvoke(STR_LUAVALUE, "checkstring", TYPE_LUASTRING, Type.NO_ARGS, Constants.INVOKEVIRTUAL));
+        append(factory.createInvoke(STR_LUAVALUE, "concat", TYPE_BUFFER, ARG_TYPES_BUFFER, Constants.INVOKEVIRTUAL));
-        append(factory.createInvoke(STR_BUFFER, "append", TYPE_BUFFER, ARG_TYPES_LUASTRING, Constants.INVOKEVIRTUAL));
+	}
+
+	public void tobuffer() {
+        append(factory.createInvoke(STR_LUAVALUE, "buffer", TYPE_BUFFER, Type.NO_ARGS, Constants.INVOKEVIRTUAL));
+	}
+
+	public void tovalue() {
+        append(factory.createInvoke(STR_BUFFER, "value", TYPE_LUAVALUE, Type.NO_ARGS, Constants.INVOKEVIRTUAL));
 	}
 }

src/jse/org/luaj/vm2/luajc/JavaGen.java

@@ -21,6 +21,7 @@
 ******************************************************************************/
 package org.luaj.vm2.luajc;
 
+import org.luaj.vm2.Buffer;
 import org.luaj.vm2.Lua;
 import org.luaj.vm2.Prototype;
 
@@ -180,12 +181,16 @@ public class JavaGen {
 					break;
 					
 				case Lua.OP_CONCAT: /*	A B C	R(A):= R(B).. ... ..R(C)			*/
-					builder.newBuffer();
+					for ( int k=b; k<=c; k++ )
-					while ( b<=c ) {
+						builder.loadLocal(pc, k);					
-						builder.loadLocal(pc, b++);
+					if ( c > b+1 ) {
-						builder.appendBuffer();
+						builder.tobuffer();
+						for ( int k=c; --k>=b; )
+							builder.concatbuffer();
+						builder.tovalue();
+					} else {
+						builder.concatvalue();
 					}
-					builder.tostring();
 					builder.storeLocal(pc, a);
 					break;