Merge pull request #231 from jboss-javassist/test/switch-case

Supporting switch-case statements with string constants.
jboss-javassist · Dec 11, 2018 · ba22607 · ba22607
2 parents 1a3d637 + c9ab465
commit ba22607
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Showing 4 changed files with 86 additions and 2 deletions.
diff --git a/Readme.html b/Readme.html
@@ -281,6 +281,11 @@ <h2>Hints</h2>
 
 <h2>Changes</h2>
 
+<p>-version 3.25
+<ul>
+    <li>GitHub Issue #72.
+</ul>
+
 <p>-version 3.24.1 on December 9, 2018
 <ul>
     <li>GitHub Issue #228, #229</li>

diff --git a/javassist.jar b/javassist.jar
diff --git a/src/main/javassist/compiler/CodeGen.java b/src/main/javassist/compiler/CodeGen.java
@@ -542,7 +542,23 @@ private void atForStmnt(Stmnt st) throws CompileError {
     }
 
     private void atSwitchStmnt(Stmnt st) throws CompileError {
+        boolean isString = false;
+        if (typeChecker != null) {
+            doTypeCheck(st.head());
+            isString = typeChecker.exprType == TypeChecker.CLASS
+                       && typeChecker.arrayDim == 0
+                       && TypeChecker.jvmJavaLangString.equals(typeChecker.className);
+        }
+
         compileExpr(st.head());
+        int tmpVar = -1;
+        if (isString) {
+            tmpVar = getMaxLocals();
+            incMaxLocals(1);
+            bytecode.addAstore(tmpVar);
+            bytecode.addAload(tmpVar);
+            bytecode.addInvokevirtual(TypeChecker.jvmJavaLangString, "hashCode", "()I");
+        }
 
         List<Integer>  prevBreakList = breakList;
         breakList = new ArrayList<Integer>();
@@ -565,6 +581,7 @@ private void atSwitchStmnt(Stmnt st) throws CompileError {
         bytecode.addGap(npairs * 8);
 
         long[] pairs = new long[npairs];
+        ArrayList<Integer> gotoDefaults = new ArrayList<Integer>();
         int ipairs = 0;
         int defaultPc = -1;
         for (ASTList list = body; list != null; list = list.tail()) {
@@ -575,9 +592,18 @@ private void atSwitchStmnt(Stmnt st) throws CompileError {
             else if (op != CASE)
                 fatal();
             else {
+                int curPos = bytecode.currentPc();
+                long caseLabel;
+                if (isString) {
+                    // computeStringLabel() also adds bytecode as its side-effects.
+                    caseLabel = (long)computeStringLabel(label.head(), tmpVar, gotoDefaults);
+                }
+                else
+                    caseLabel = (long)computeLabel(label.head());
+
                 pairs[ipairs++]
-                    = ((long)computeLabel(label.head()) << 32) + 
-                      ((long)(bytecode.currentPc() - opcodePc) & 0xffffffff);
+                    = (caseLabel << 32) + 
+                      ((long)(curPos - opcodePc) & 0xffffffff);
             }
 
             hasReturned = false;
@@ -600,6 +626,8 @@ else if (op != CASE)
             defaultPc = endPc;
 
         bytecode.write32bit(opcodePc2, defaultPc - opcodePc);
+        for (int addr: gotoDefaults)
+            bytecode.write16bit(addr, defaultPc - addr + 1);
 
         patchGoto(breakList, endPc);
         breakList = prevBreakList;
@@ -613,6 +641,26 @@ private int computeLabel(ASTree expr) throws CompileError {
         throw new CompileError("bad case label");
     }
 
+    private int computeStringLabel(ASTree expr, int tmpVar, List<Integer> gotoDefaults)
+        throws CompileError
+    {
+        doTypeCheck(expr);
+        expr = TypeChecker.stripPlusExpr(expr);
+        if (expr instanceof StringL) {
+            String label = ((StringL)expr).get();
+            bytecode.addAload(tmpVar);
+            bytecode.addLdc(label);
+            bytecode.addInvokevirtual(TypeChecker.jvmJavaLangString, "equals",
+                                      "(Ljava/lang/Object;)Z");
+            bytecode.addOpcode(IFEQ);
+            Integer pc = Integer.valueOf(bytecode.currentPc());
+            bytecode.addIndex(0);
+            gotoDefaults.add(pc);
+            return (int)label.hashCode();
+        }
+        throw new CompileError("bad case label");
+    }
+
     private void atBreakStmnt(Stmnt st, boolean notCont)
         throws CompileError
     {

diff --git a/src/test/javassist/JvstTest5.java b/src/test/javassist/JvstTest5.java
@@ -453,4 +453,35 @@ public void testNestHostAttributeCopy() throws Exception {
         cc.getClassFile().compact();
         cc.toClass(test5.DefineClassCapability.class);
     }
+
+    public void testSwitchCaseWithStringConstant() throws Exception {
+        CtClass cc = sloader.get("test5.SwitchCase");
+        cc.addMethod(CtNewMethod.make(
+                "public int run() {" +
+                "    String s = \"foobar\";\n" +
+                "    switch (s) {\n" +
+                "    case STR1: return 1;\n" +
+                "    case \"foobar\": return 2;\n" +
+                "    default: return 3; }\n" +
+                "}\n", cc));
+        cc.writeFile();
+        Object obj = make(cc.getName());
+        assertEquals(2, invoke(obj, "run"));   
+    }
+
+    public void testSwitchCaseWithStringConstant2() throws Exception {
+        CtClass cc = sloader.makeClass("test5.SwitchCase2");
+        cc.addMethod(CtNewMethod.make(
+                "public int run() {" +
+                "    String s = \"foo\";\n" +
+                "    switch (s) {\n" +
+                "    case test5.SwitchCase.STR1: return 1;\n" +
+                "    case \"foobar\": return 2;\n" +
+                "    }\n" +
+                "    return 3;\n" +
+                "}\n", cc));
+        cc.writeFile();
+        Object obj = make(cc.getName());
+        assertEquals(1, invoke(obj, "run"));   
+    }
 }