net: Change type of UploadData::elements from std::vector to ScopedVector

ipc/ipc_message_utils.h

Index: ipc/ipc_message_utils.h
diff --git a/ipc/ipc_message_utils.h b/ipc/ipc_message_utils.h
index 0e4c68e513efbbc9b6a0651e625a5978dc724739..d5817d2f7c90cbf8d90875331725436aaa512ea2 100644
--- a/ipc/ipc_message_utils.h
+++ b/ipc/ipc_message_utils.h
@@ -12,6 +12,7 @@
 #include <vector>
 
 #include "base/format_macros.h"
+#include "base/memory/scoped_vector.h"
 #include "base/platform_file.h"
 #include "base/string16.h"
 #include "base/stringprintf.h"
@@ -633,6 +634,34 @@ struct ParamTraits< Tuple5<A, B, C, D, E> > {
   }
 };
 
+template<class P>
+struct ParamTraits<ScopedVector<P> > {
+  typedef ScopedVector<P> param_type;
+  static void Write(Message* m, const param_type& p) {
+    WriteParam(m, static_cast<int>(p.size()));
+    for (size_t i = 0; i < p.size(); i++)
+      WriteParam(m, *p[i]);
+  }
+  static bool Read(const Message* m, PickleIterator* iter, param_type* r) {
+    int size = 0;
+    if (!m->ReadLength(iter, &size))
+      return false;
+    for (int i = 0; i < size; i++) {

[jam, 2012/11/12 20:58:54]

you should do error checking just like std::vector does, i.e. the
 if (INT_MAX / sizeof(P) <= static_cast<size_t>(size))
 322       return false;	 323       return false;

[hashimoto, 2012/11/13 05:03:51]

What is still unclear for me is that do we need to replace "sizeof(P)" here with
"sizeof(P*)" or not.
Since ScopedVector<P> is virtually a std::vector<P*>, perhaps INT_MAX/sizeof(P*)
might make more sense.

INT_MAX/sizeof(P) may work better in some cases if we want to avoid consuming
memory more than INT_MAX bytes (=2GB), but it does not work for some cases
including net::UploadElement because net::UploadElement has a std::vector as its
member and sizeof(std::vector<P>) is constant (i.e. sizeof(std::vector) cannot
know how much heap does the vector consume)
It means "INT_MAX > size*sizeof(P)" cannot guarantee that the total memory
consumed by the deserialized ScopedVector<P> not exceeding INT_MAX bytes when P
holds data on heap.

Anyways, I leave INT_MAX/sizeof(P) here for now.

+      r->push_back(new P());
+      if (!ReadParam(m, iter, r->back()))
+        return false;
+    }
+    return true;
+  }
+  static void Log(const param_type& p, std::string* l) {
+    for (size_t i = 0; i < p.size(); ++i) {
+      if (i != 0)
+        l->append(" ");
+      LogParam(*p[i], l);
+    }
+  }
+};
+
 // IPC types ParamTraits -------------------------------------------------------
 
 // A ChannelHandle is basically a platform-inspecific wrapper around the