Add a GetSignature() method to dbus::MessageReader.

dbus/message.cc

Index: dbus/message.cc
diff --git a/dbus/message.cc b/dbus/message.cc
index c9219b7e52bd3be8f70d9500c92a02df1472d856..9db0a52d8ecad4430ef3dcf4aa99609e9b28545e 100644
--- a/dbus/message.cc
+++ b/dbus/message.cc
@@ -42,6 +42,12 @@ void AppendUint32Header(const std::string& header_name,
   }
 }
 
+struct DBusFreeDeleter {
+  inline void operator()(void* ptr) const {
+    dbus_free(ptr);
+  }
+};
+
 }  // namespace
 
 namespace dbus {
@@ -262,7 +268,7 @@ std::string Message::ToString() {
   AppendStringHeader("member", GetMember(), &headers);
   AppendStringHeader("error_name", GetErrorName(), &headers);
   AppendStringHeader("sender", GetSender(), &headers);
-  AppendStringHeader("signature", GetSignature(), &headers);
+  AppendStringHeader("signature", GetDataSignature(), &headers);
   AppendUint32Header("serial", GetSerial(), &headers);
   AppendUint32Header("reply_serial", GetReplySerial(), &headers);
 
@@ -333,7 +339,7 @@ std::string Message::GetSender() {
   return sender ? sender : "";
 }
 
-std::string Message::GetSignature() {
+std::string Message::GetDataSignature() {
   const char* signature = dbus_message_get_signature(raw_message_);
   return signature ? signature : "";
 }
@@ -935,6 +941,12 @@ Message::DataType MessageReader::GetDataType() {
   return static_cast<Message::DataType>(dbus_type);
 }
 
+std::string MessageReader::GetDataSignature() {
+  scoped_ptr<char, DBusFreeDeleter> signature(
+      dbus_message_iter_get_signature(&raw_message_iter_));

[satorux1, 2014/08/25 05:33:27]

I understand the intention, but I guess calling dbus_free() is simpler. In fact,
it's not obvious if "scoped_ptr<char" is correct or "scoped_ptr<char*" is
correct here.

string signature;
char* raw_signature = dbus_message_iter_get_signature(...);
if (raw_signature) {
   signature = raw_signature;
   dbus_free(raw_signature);
}
return signature;

[Ben Chan, 2014/08/25 05:43:07]

Done.

+  return signature ? signature.get() : "";
+}
+
 bool MessageReader::CheckDataType(int dbus_type) {
   const int actual_type = dbus_message_iter_get_arg_type(&raw_message_iter_);
   if (actual_type != dbus_type) {