Merge from google internal

1 files changed, 11 insertions, 4 deletions

diff --git a/src/google/protobuf/arena.h b/src/google/protobuf/arena.h
index a0cee22b..32be9a17 100644
--- a/src/google/protobuf/arena.h
+++ b/src/google/protobuf/arena.h
@@ -61,7 +61,7 @@ class Arena;       // defined below
 class Message;     // message.h
 
 namespace internal {
-class ArenaString; // arenastring.h
+struct ArenaStringPtr;  // arenastring.h
 class LazyField;   // lazy_field.h
 
 template<typename Type>
@@ -223,6 +223,14 @@ class LIBPROTOBUF_EXPORT Arena {
     Init(options);
   }
 
+  // Block overhead.  Use this as a guide for how much to over-allocate the
+  // initial block if you want an allocation of size N to fit inside it.
+  //
+  // WARNING: if you allocate multiple objects, it is difficult to guarantee
+  // that a series of allocations will fit in the initial block, especially if
+  // Arena changes its alignment guarantees in the future!
+  static const size_t kBlockOverhead = internal::ArenaImpl::kHeaderSize;
+
   // Default constructor with sensible default options, tuned for average
   // use-cases.
   Arena() : impl_(ArenaOptions()) { Init(ArenaOptions()); }
@@ -524,10 +532,9 @@ class LIBPROTOBUF_EXPORT Arena {
   // returns the total space used by the arena which is the sums of the sizes
   // of the allocated blocks. This method is not thread-safe.
   GOOGLE_PROTOBUF_ATTRIBUTE_NOINLINE uint64 Reset() {
-    uint64 space_allocated = SpaceAllocated();
     // Call the reset hook
     if (on_arena_reset_ != NULL) {
-      on_arena_reset_(this, hooks_cookie_, space_allocated);
+      on_arena_reset_(this, hooks_cookie_, impl_.SpaceAllocated());
     }
     return impl_.Reset();
   }
@@ -912,7 +919,7 @@ class LIBPROTOBUF_EXPORT Arena {
 
   template <typename Type>
   friend class ::google::protobuf::internal::GenericTypeHandler;
-  friend class internal::ArenaString;  // For AllocateAligned.
+  friend struct internal::ArenaStringPtr;  // For AllocateAligned.
   friend class internal::LazyField;    // For CreateMaybeMessage.
   template <typename Key, typename T>
   friend class Map;