fixed a crash bug in rendering the root name.

added a test case to catch this bug.


git-svn-id: svn://bind10.isc.org/svn/bind10/branches/parkinglot@630 e5f2f494-b856-4b98-b285-d166d9295462

src/lib/dns/cpp/messagerenderer.cc

@@ -219,7 +219,8 @@ MessageRenderer::writeName(const Name& name, bool compress)
     name.toWire(impl_->nbuffer_);
 
     unsigned int i;
-    std::set<NameCompressNode>::const_iterator n;
+    std::set<NameCompressNode>::const_iterator notfound = impl_->nodeset_.end();
+    std::set<NameCompressNode>::const_iterator n = notfound;
 
     // Find the longest ancestor name in the rendered set that matches the
     // given name.
@@ -231,7 +232,7 @@ MessageRenderer::writeName(const Name& name, bool compress)
         n = impl_->nodeset_.find(NameCompressNode(impl_->nbuffer_, i,
                                                   impl_->nbuffer_.getLength() -
                                                   i));
-        if (n != impl_->nodeset_.end()) {
+        if (n != notfound) {
             break;
         }
     }
@@ -241,7 +242,7 @@ MessageRenderer::writeName(const Name& name, bool compress)
     // Write uncompress part...
     impl_->buffer_.writeData(impl_->nbuffer_.getData(),
                              compress ? i : impl_->nbuffer_.getLength());
-    if (compress && n != impl_->nodeset_.end()) {
+    if (compress && n != notfound) {
         // ...and compression pointer if available.
         uint16_t pointer = (*n).pos_;
         pointer |= Name::COMPRESS_POINTER_MARK16;

src/lib/dns/cpp/messagerenderer_unittest.cc

@@ -113,4 +113,24 @@ TEST_F(MessageRendererTest, writeNameCaseCompress)
     EXPECT_PRED_FORMAT4(UnitTestUtil::matchWireData, buffer.getData(),
                         buffer.getLength(), &data[0], data.size());
 }
+
+TEST_F(MessageRendererTest, writeRootName)
+{
+    // root name is special: it never causes compression or can (reasonably)
+    // be a compression pointer.  So it makes sense to check this case
+    // explicitly.
+    Name example_name = Name("www.example.com");
+
+    OutputBuffer expected(0);
+    expected.writeUint8(0);     // root name
+    example_name.toWire(expected);
+
+    renderer.writeName(Name("."));
+    renderer.writeName(example_name);
+    EXPECT_PRED_FORMAT4(UnitTestUtil::matchWireData,
+                        static_cast<const uint8_t*>(buffer.getData()),
+                        buffer.getLength(),
+                        static_cast<const uint8_t*>(expected.getData()),
+                        expected.getLength());
+}
 }