Add a variadic version of ParamTraits, to allow for >5 IPC parameters.

ipc/ipc_message_utils.h

 // Copyright (c) 2012 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 <limits.h>
 #include <stddef.h>
 #include <stdint.h>
@@ skipping 706 matching lines @@
   static void Write(base::Pickle* m, const param_type& p) {}
   static bool Read(const base::Pickle* m,
                    base::PickleIterator* iter,
                    param_type* r) {
     return true;
   }
   static void Log(const param_type& p, std::string* l) {
   }
 };
 
-template <class A>
-struct ParamTraits<std::tuple<A>> {
-  typedef std::tuple<A> param_type;
+template <typename T, int I, int COUNT>

[Ken Rockot(use gerrit already), 2017/06/20 16:35:53]

super nitty nit: The style guide seems to be silent on this issue, but I would
prefer that this code use normal naming conventions (i.e., typenames are
CamelCase, variable names are snake_case) for the template arg names. So
something like:

  template <typename T, int index, int count>

instead of the LOUDCASE used here.

+struct TupleParamTraitsHelper {
+  using Next = TupleParamTraitsHelper<T, I + 1, COUNT>;
+
+  static void GetSize(base::PickleSizer* sizer, const T& p) {
+    GetParamSize(sizer, std::get<I>(p));
+    Next::GetSize(sizer, p);
+  }
+
+  static void Write(base::Pickle* m, const T& p) {
+    WriteParam(m, std::get<I>(p));
+    Next::Write(m, p);
+  }
+
+  static bool Read(const base::Pickle* m, base::PickleIterator* iter, T* r) {
+    return ReadParam(m, iter, &std::get<I>(*r)) && Next::Read(m, iter, r);
+  }
+
+  static void Log(const T& p, std::string* l) {
+    LogParam(std::get<I>(p), l);
+    if (I < COUNT - 1)
+      l->append(", ");
+    Next::Log(p, l);
+  }
+};
+
+template <typename T, int I>
+struct TupleParamTraitsHelper<T, I, I> {
+  static void GetSize(base::PickleSizer* sizer, const T& p) {}
+  static void Write(base::Pickle* m, const T& p) {}
+  static bool Read(const base::Pickle* m, base::PickleIterator* iter, T* r) {
+    return true;
+  }
+  static void Log(const T& p, std::string* l) {}
+};
+
+template <class... Args>

[Ken Rockot(use gerrit already), 2017/06/20 16:35:53]

nit: for consistency with most new code please consider writing typename...
instead of class...

+struct ParamTraits<std::tuple<Args...>> {
+  using param_type = std::tuple<Args...>;
+  using Helper =
+      TupleParamTraitsHelper<param_type, 0, std::tuple_size<param_type>::value>;
+
   static void GetSize(base::PickleSizer* sizer, const param_type& p) {
-    GetParamSize(sizer, std::get<0>(p));
+    Helper::GetSize(sizer, p);
   }
+
   static void Write(base::Pickle* m, const param_type& p) {
-    WriteParam(m, std::get<0>(p));
+    Helper::Write(m, p);
   }
+
   static bool Read(const base::Pickle* m,
                    base::PickleIterator* iter,
                    param_type* r) {
-    return ReadParam(m, iter, &std::get<0>(*r));
+    return Helper::Read(m, iter, r);
   }
-  static void Log(const param_type& p, std::string* l) {
-    LogParam(std::get<0>(p), l);
-  }
-};
 
-template <class A, class B>
-struct ParamTraits<std::tuple<A, B>> {
-  typedef std::tuple<A, B> param_type;
-  static void GetSize(base::PickleSizer* sizer, const param_type& p) {
-    GetParamSize(sizer, std::get<0>(p));
-    GetParamSize(sizer, std::get<1>(p));
-  }
-  static void Write(base::Pickle* m, const param_type& p) {
-    WriteParam(m, std::get<0>(p));
-    WriteParam(m, std::get<1>(p));
-  }
-  static bool Read(const base::Pickle* m,
-                   base::PickleIterator* iter,
-                   param_type* r) {
-    return (ReadParam(m, iter, &std::get<0>(*r)) &&
-            ReadParam(m, iter, &std::get<1>(*r)));
-  }
-  static void Log(const param_type& p, std::string* l) {
-    LogParam(std::get<0>(p), l);
-    l->append(", ");
-    LogParam(std::get<1>(p), l);
-  }
-};
-
-template <class A, class B, class C>
-struct ParamTraits<std::tuple<A, B, C>> {
-  typedef std::tuple<A, B, C> param_type;
-  static void GetSize(base::PickleSizer* sizer, const param_type& p) {
-    GetParamSize(sizer, std::get<0>(p));
-    GetParamSize(sizer, std::get<1>(p));
-    GetParamSize(sizer, std::get<2>(p));
-  }
-  static void Write(base::Pickle* m, const param_type& p) {
-    WriteParam(m, std::get<0>(p));
-    WriteParam(m, std::get<1>(p));
-    WriteParam(m, std::get<2>(p));
-  }
-  static bool Read(const base::Pickle* m,
-                   base::PickleIterator* iter,
-                   param_type* r) {
-    return (ReadParam(m, iter, &std::get<0>(*r)) &&
-            ReadParam(m, iter, &std::get<1>(*r)) &&
-            ReadParam(m, iter, &std::get<2>(*r)));
-  }
-  static void Log(const param_type& p, std::string* l) {
-    LogParam(std::get<0>(p), l);
-    l->append(", ");
-    LogParam(std::get<1>(p), l);
-    l->append(", ");
-    LogParam(std::get<2>(p), l);
-  }
-};
-
-template <class A, class B, class C, class D>
-struct ParamTraits<std::tuple<A, B, C, D>> {
-  typedef std::tuple<A, B, C, D> param_type;
-  static void GetSize(base::PickleSizer* sizer, const param_type& p) {
-    GetParamSize(sizer, std::get<0>(p));
-    GetParamSize(sizer, std::get<1>(p));
-    GetParamSize(sizer, std::get<2>(p));
-    GetParamSize(sizer, std::get<3>(p));
-  }
-  static void Write(base::Pickle* m, const param_type& p) {
-    WriteParam(m, std::get<0>(p));
-    WriteParam(m, std::get<1>(p));
-    WriteParam(m, std::get<2>(p));
-    WriteParam(m, std::get<3>(p));
-  }
-  static bool Read(const base::Pickle* m,
-                   base::PickleIterator* iter,
-                   param_type* r) {
-    return (ReadParam(m, iter, &std::get<0>(*r)) &&
-            ReadParam(m, iter, &std::get<1>(*r)) &&
-            ReadParam(m, iter, &std::get<2>(*r)) &&
-            ReadParam(m, iter, &std::get<3>(*r)));
-  }
-  static void Log(const param_type& p, std::string* l) {
-    LogParam(std::get<0>(p), l);
-    l->append(", ");
-    LogParam(std::get<1>(p), l);
-    l->append(", ");
-    LogParam(std::get<2>(p), l);
-    l->append(", ");
-    LogParam(std::get<3>(p), l);
-  }
-};
-
-template <class A, class B, class C, class D, class E>
-struct ParamTraits<std::tuple<A, B, C, D, E>> {
-  typedef std::tuple<A, B, C, D, E> param_type;
-  static void GetSize(base::PickleSizer* sizer, const param_type& p) {
-    GetParamSize(sizer, std::get<0>(p));
-    GetParamSize(sizer, std::get<1>(p));
-    GetParamSize(sizer, std::get<2>(p));
-    GetParamSize(sizer, std::get<3>(p));
-    GetParamSize(sizer, std::get<4>(p));
-  }
-  static void Write(base::Pickle* m, const param_type& p) {
-    WriteParam(m, std::get<0>(p));
-    WriteParam(m, std::get<1>(p));
-    WriteParam(m, std::get<2>(p));
-    WriteParam(m, std::get<3>(p));
-    WriteParam(m, std::get<4>(p));
-  }
-  static bool Read(const base::Pickle* m,
-                   base::PickleIterator* iter,
-                   param_type* r) {
-    return (ReadParam(m, iter, &std::get<0>(*r)) &&
-            ReadParam(m, iter, &std::get<1>(*r)) &&
-            ReadParam(m, iter, &std::get<2>(*r)) &&
-            ReadParam(m, iter, &std::get<3>(*r)) &&
-            ReadParam(m, iter, &std::get<4>(*r)));
-  }
-  static void Log(const param_type& p, std::string* l) {
-    LogParam(std::get<0>(p), l);
-    l->append(", ");
-    LogParam(std::get<1>(p), l);
-    l->append(", ");
-    LogParam(std::get<2>(p), l);
-    l->append(", ");
-    LogParam(std::get<3>(p), l);
-    l->append(", ");
-    LogParam(std::get<4>(p), l);
-  }
+  static void Log(const param_type& p, std::string* l) { Helper::Log(p, l); }
 };
 
 template <class P, size_t stack_capacity>
 struct ParamTraits<base::StackVector<P, stack_capacity> > {
   typedef base::StackVector<P, stack_capacity> param_type;
   static void GetSize(base::PickleSizer* sizer, const param_type& p) {
     GetParamSize(sizer, static_cast<int>(p->size()));
     for (size_t i = 0; i < p->size(); i++)
       GetParamSize(sizer, p[i]);
   }
@@ skipping 316 matching lines @@
 template <class ReplyParamType>
 inline void LogReplyParamsToMessage(const ReplyParamType& reply_params,
                                     const Message* msg) {}
 
 inline void ConnectMessageAndReply(const Message* msg, Message* reply) {}
 #endif
 
 }  // namespace IPC
 
 #endif  // IPC_IPC_MESSAGE_UTILS_H_