Avoid heap allocations in IPAddress

ppapi/shared_impl/private/net_address_private_impl.cc

Index: ppapi/shared_impl/private/net_address_private_impl.cc
diff --git a/ppapi/shared_impl/private/net_address_private_impl.cc b/ppapi/shared_impl/private/net_address_private_impl.cc
index d410d8f28dbe7286b1e5b78391c2a2db00623dd5..43ffbe4a02d57e83e837d31dc45f232bab3cca04 100644
--- a/ppapi/shared_impl/private/net_address_private_impl.cc
+++ b/ppapi/shared_impl/private/net_address_private_impl.cc
@@ -9,6 +9,7 @@
 
 #include <string>
 
+#include "base/containers/stack_container.h"
 #include "base/logging.h"
 #include "base/strings/stringprintf.h"
 #include "build/build_config.h"
@@ -451,7 +452,7 @@ bool NetAddressPrivateImpl::SockaddrToNetAddress(
 
 // static
 bool NetAddressPrivateImpl::IPEndPointToNetAddress(
-    const std::vector<uint8_t>& address,
+    const net::IPAddress::IPAddressBytes& address,
     uint16_t port,
     PP_NetAddress_Private* addr) {
   if (!addr)
@@ -484,7 +485,7 @@ bool NetAddressPrivateImpl::IPEndPointToNetAddress(
 // static
 bool NetAddressPrivateImpl::NetAddressToIPEndPoint(
     const PP_NetAddress_Private& addr,
-    std::vector<uint8_t>* address,
+    base::StackVector<uint8_t, 16>* address,
     uint16_t* port) {
   if (!address || !port)
     return false;
@@ -495,7 +496,8 @@ bool NetAddressPrivateImpl::NetAddressToIPEndPoint(
 
   *port = net_addr->port;
   size_t address_size = GetAddressSize(net_addr);
-  address->assign(&net_addr->address[0], &net_addr->address[address_size]);
+  address->container().assign(&net_addr->address[0],
+                              &net_addr->address[address_size]);

[eroman, 2017/05/19 22:00:07]

Technically this existing code was relying on undefined behavior (indexing
beyond the end of the array), even if only to get the address.

Can you change it to not use operator[]? Say:

   assign(net_addr->address, net_addr->address + address_size);

[Ryan Hamilton, 2017/05/20 03:21:44]

As per your previous comment, I switched this to take an IPAddressBytes instead
of a StackVector, which does not have an assign method. Instead I push_back the
bytes 1 at a time. (Of course, it's pushing back into an array so it's not going
to reallocate or anything)

[eroman, 2017/05/22 18:06:44]

This translation presumes that |address| is the empty address upon entry, which
I don't think is guaranteed by the API. It would be prudent to call Resize(0)
first to address this.

Or better yet, add an Assign() method that takes ptr + size  (and change the
constructor to call this as a helper).

[Ryan Hamilton, 2017/05/22 22:12:32]

Done.

 
   return true;
 }