Add a nullable string16 class to base. It combines a string16 + a null param...

ipc/ipc_message_utils.h

 // Copyright (c) 2006-2009 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef IPC_IPC_MESSAGE_UTILS_H_
 #define IPC_IPC_MESSAGE_UTILS_H_
 
 #include <string>
 #include <vector>
 #include <map>
 
 #include "base/file_path.h"
 #include "base/format_macros.h"
+#include "base/nullable_string16.h"
 #include "base/string16.h"
 #include "base/string_util.h"
 #include "base/time.h"
 #include "base/tuple.h"
 #include "base/values.h"
 #if defined(OS_POSIX)
 #include "ipc/file_descriptor_set_posix.h"
 #endif
 #include "ipc/ipc_channel_handle.h"
 #include "ipc/ipc_sync_message.h"
@@ skipping 514 matching lines @@
   }
   static void Log(const param_type& p, std::wstring* l) {
     l->append(L"(");
     LogParam(p.first, l);
     l->append(L", ");
     LogParam(p.second, l);
     l->append(L")");
   }
 };
 
+template <>
+struct ParamTraits<NullableString16> {
+  typedef NullableString16 param_type;
+  static void Write(Message* m, const param_type& p) {
+    WriteParam(m, p.string());
+    WriteParam(m, p.is_null());
+  }
+  static bool Read(const Message* m, void** iter, param_type* r) {
+    string16 string;
+    if (!ReadParam(m, iter, &string))
+      return false;
+    bool is_null;
+    if (!ReadParam(m, iter, &is_null))
+      return false;
+    *r = NullableString16(string, is_null);
+    return true;
+  }
+  static void Log(const param_type& p, std::wstring* l) {
+    l->append(L"(");
+    LogParam(p.string(), l);
+    l->append(L", ");
+    LogParam(p.is_null(), l);
+    l->append(L")");
+  }
+};
+
 // If WCHAR_T_IS_UTF16 is defined, then string16 is a std::wstring so we don't
 // need this trait.
 #if !defined(WCHAR_T_IS_UTF16)
 template <>
 struct ParamTraits<string16> {
   typedef string16 param_type;
   static void Write(Message* m, const param_type& p) {
     m->WriteString16(p);
   }
   static bool Read(const Message* m, void** iter, param_type* r) {
@@ skipping 675 matching lines @@
     ReplyParam p(a, b, c, d, e);
     WriteParam(reply, p);
   }
 };
 
 //-----------------------------------------------------------------------------
 
 }  // namespace IPC
 
 #endif  // IPC_IPC_MESSAGE_UTILS_H_