Reconcile C & Java typechecking on table.concat() and string .. concat operator

src/core/org/luaj/lib/TableLib.java

@@ -98,26 +98,17 @@ public class TableLib extends LFunction {
 			int n = vm.gettop();
 			LTable table = vm.totable(2);
 			LString sep = (n>=3? vm.tolstring(3): null);
-			int i = vm.tointeger(4);
-			int j = vm.tointeger(5);
-			int len = table.luaLength();
-			if ( i == 0 ) 
-				i = 1;
-			if ( j == 0 ) 
-				j = len;
+			int i = (n>=4? vm.tointeger(4): 1);
+			int j = (n>=5? vm.tointeger(5): table.luaLength());
 			ByteArrayOutputStream baos = new ByteArrayOutputStream();
-			try {
-				for ( int k=i; k<=j; k++ ) {
-					LValue v = table.get(k);
-						v.luaAsString().write(baos);
-						if ( k<j && sep!=null )
-							sep.write( baos );
-				}
-				vm.resettop();
-				vm.pushlstring( baos.toByteArray() );
-			} catch (IOException e) {
-				vm.error(e.getMessage());
+			for ( int k=i; k<=j; k++ ) {
+				LValue v = table.get(k);
+				v.luaConcatTo(baos);
+				if ( k<j && sep!=null )
+					sep.luaConcatTo( baos );
 			}
+			vm.resettop();
+			vm.pushlstring( baos.toByteArray() );
 			break;
 		}
 		

src/core/org/luaj/vm/LNumber.java

@@ -21,6 +21,8 @@
 ******************************************************************************/
 package org.luaj.vm;
 
+import java.io.ByteArrayOutputStream;
+
 
 abstract
 public class LNumber extends LValue {
@@ -83,4 +85,9 @@ public class LNumber extends LValue {
 		return this;
 	}
 
+	/** Write as a string */
+	public void luaConcatTo(ByteArrayOutputStream baos) {
+		luaAsString().luaConcatTo( baos );
+	}
+
 }

src/core/org/luaj/vm/LString.java

@@ -22,6 +22,7 @@
 package org.luaj.vm;
 
 import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.io.OutputStream;
 
@@ -262,23 +263,6 @@ public class LString extends LValue {
 		return new LString( s );
 	}
 	
-	public static LString concat( final LString[] strings ) {
-		int length = 0;
-		for ( int i = 0; i < strings.length; ++i ) {
-			length += strings[i].length();
-		}
-		byte[] bytes = new byte[length];
-		
-		for ( int i = 0, offset = 0; i < strings.length; ++i ) {
-			LString s = strings[i];
-			final int len = s.length();
-			System.arraycopy( s.m_bytes, s.m_offset, bytes, offset, len );
-			offset += len;
-		}
-		
-		return new LString( bytes );
-	}
-	
 	/**
 	 * Write the specified substring of this string to the given output stream.
 	 */
@@ -437,5 +421,8 @@ public class LString extends LValue {
 		return m_bytes[m_offset + index] & 0x0FF;
 	}
 
+	public void luaConcatTo(ByteArrayOutputStream baos) {
+		baos.write( m_bytes, m_offset, m_length );
+	}
 
 }

src/core/org/luaj/vm/LValue.java

@@ -21,6 +21,8 @@
 ******************************************************************************/
 package org.luaj.vm;
 
+import java.io.ByteArrayOutputStream;
+
 
 abstract
 public class LValue {
@@ -322,4 +324,9 @@ public class LValue {
 	public LValue toStrongReference() {
 		return this;
 	}
+
+	/** Concatenate this value to a ByteArrayOutputStream */
+	public void luaConcatTo(ByteArrayOutputStream baos) {
+		throw new LuaErrorException( "attempt to concat ? (a "+luaGetTypeName()+" value)");
+	}
 }

src/core/org/luaj/vm/LuaState.java

@@ -639,13 +639,11 @@ public class LuaState extends Lua {
                 b = LuaState.GETARG_B(i);
                 c = LuaState.GETARG_C(i);
                 int numValues = c - b + 1;
-                LString[] strings = new LString[numValues];
-                
+                ByteArrayOutputStream baos = new ByteArrayOutputStream();
                 for (int j = b, l = 0; j <= c; j++, l++) {
-                    LString s = this.stack[base + j].luaAsString();
-                    strings[l] = s;
+                    this.stack[base + j].luaConcatTo( baos );
                 }
-                this.stack[base + a] = LString.concat( strings );
+                this.stack[base + a] = new LString( baos.toByteArray() );
                 continue;
             }
             case LuaState.OP_JMP: {

src/test/res/errors.lua

@@ -60,6 +60,33 @@ print( 'a(-a)  ', a(function() return -a end) )
 print( 'a(-s)  ', a(function() return -s end) )
 print( 'a(-true)', a(function() local b = true; return -b end) )
 
+-- string concatenation
+local function concatsuite(comparefunc) 
+	print( '"a".."b"', comparefunc("a","b") )
+	print( '"a"..nil', comparefunc("a",nil) )
+	print( 'nil.."b"', comparefunc(nil,"b") )
+	print( '"a"..{}', comparefunc("a",{}) )
+	print( '{}.."b"', comparefunc({},"b") )
+	print( '"a"..2', comparefunc("a",2) )
+	print( '2.."b"', comparefunc(2,"b") )
+	print( '"a"..print', comparefunc("a",print) )
+	print( 'print.."b"', comparefunc(print,"b") )
+	print( '"a"..true', comparefunc("a",true) )
+	print( 'true.."b"', comparefunc(true,"b") )
+	print( 'nil..true', comparefunc(nil,true) )
+	print( '"a"..3.5', comparefunc("a",3.5) )
+	print( '3.5.."b"', comparefunc(3.5,"b") )
+end
+local function strconcat(a,b)
+	return pcall( function() return a..b end ) 
+end
+local function tblconcat(a,b) 
+	local t={a,b}
+	return pcall( function() return table.concat(t,'-') end )
+end
+-- concatsuite(strconcat)
+concatsuite(tblconcat)
+
 -- pairs
 print( 'a(pairs(nil))', a(function() return id(pairs(nil,{})) end) )
 print( 'a(pairs(a))  ', a(function() return id(pairs(a,{})) end) )