diff -r 000000000000 -r eaf4e8387065 vm/src/main/java/org/apidesign/vm4brwsr/LocalsMapper.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/vm/src/main/java/org/apidesign/vm4brwsr/LocalsMapper.java	Wed Dec 12 11:04:02 2012 +0100
@@ -0,0 +1,141 @@
+/**
+ * Back 2 Browser Bytecode Translator
+ * Copyright (C) 2012 Jaroslav Tulach <jaroslav.tulach@apidesign.org>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. Look for COPYING file in the top folder.
+ * If not, see http://opensource.org/licenses/GPL-2.0.
+ */
+package org.apidesign.vm4brwsr;
+
+import java.io.IOException;
+import org.apidesign.javap.RuntimeConstants;
+import org.apidesign.javap.TypeArray;
+
+public final class LocalsMapper {
+    private final TypeArray argTypeRecords;
+    private final TypeArray localTypeRecords;
+
+    public LocalsMapper(final TypeArray stackMapArgs) {
+        final TypeArray initTypeRecords = new TypeArray();
+        updateRecords(initTypeRecords, stackMapArgs);
+
+        argTypeRecords = initTypeRecords;
+        localTypeRecords = new TypeArray(initTypeRecords);
+    }
+
+    public void outputArguments(final Appendable out) throws IOException {
+        final int argRecordCount = argTypeRecords.getSize();
+        if (argRecordCount > 0) {
+            Variable variable = getVariable(argTypeRecords, 0);
+            out.append(variable);
+
+            int i = variable.isCategory2() ? 2 : 1;
+            while (i < argRecordCount) {
+                variable = getVariable(argTypeRecords, i);
+                out.append(", ");
+                out.append(variable);
+                i += variable.isCategory2() ? 2 : 1;
+            }
+        }
+    }
+
+    public void syncWithFrameLocals(final TypeArray frameLocals) {
+        updateRecords(localTypeRecords, frameLocals);
+    }
+
+    public Variable setI(final int index) {
+        return setT(index, VarType.INTEGER);
+    }
+
+    public Variable setL(final int index) {
+        return setT(index, VarType.LONG);
+    }
+
+    public Variable setF(final int index) {
+        return setT(index, VarType.FLOAT);
+    }
+
+    public Variable setD(final int index) {
+        return setT(index, VarType.DOUBLE);
+    }
+
+    public Variable setA(final int index) {
+        return setT(index, VarType.REFERENCE);
+    }
+
+    public Variable setT(final int index, final int type) {
+        updateRecord(localTypeRecords, index, type);
+        return Variable.getLocalVariable(type, index);
+    }
+
+    public Variable getI(final int index) {
+        return getT(index, VarType.INTEGER);
+    }
+
+    public Variable getL(final int index) {
+        return getT(index, VarType.LONG);
+    }
+
+    public Variable getF(final int index) {
+        return getT(index, VarType.FLOAT);
+    }
+
+    public Variable getD(final int index) {
+        return getT(index, VarType.DOUBLE);
+    }
+
+    public Variable getA(final int index) {
+        return getT(index, VarType.REFERENCE);
+    }
+
+    public Variable getT(final int index, final int type) {
+        final int oldRecordValue = localTypeRecords.get(index);
+        if ((oldRecordValue & 0xff) != type) {
+            throw new IllegalStateException("Type mismatch");
+        }
+
+        return Variable.getLocalVariable(type, index);
+    }
+
+    private static void updateRecords(final TypeArray typeRecords,
+                                      final TypeArray stackMapTypes) {
+        final int srcSize = stackMapTypes.getSize();
+        for (int i = 0, dstIndex = 0; i < srcSize; ++i) {
+            final int smType = stackMapTypes.get(i);
+            if (smType == RuntimeConstants.ITEM_Bogus) {
+                ++dstIndex;
+                continue;
+            }
+            final int varType = VarType.fromStackMapType(smType);
+            updateRecord(typeRecords, dstIndex, varType);
+            dstIndex += VarType.isCategory2(varType) ? 2 : 1;
+        }
+    }
+
+    private static void updateRecord(final TypeArray typeRecords,
+                                     final int index, final int type) {
+        if (typeRecords.getSize() < (index + 1)) {
+            typeRecords.setSize(index + 1);
+        }
+
+        final int oldRecordValue = typeRecords.get(index);
+        final int usedTypesMask =
+                (oldRecordValue >> 8) | (1 << type);
+        typeRecords.set(index, (usedTypesMask << 8) | type);
+    }
+
+    private static Variable getVariable(final TypeArray typeRecords,
+                                        final int index) {
+        return Variable.getLocalVariable(typeRecords.get(index) & 0xff, index);
+    }
+}