Author: Daniel Lin <danielin@umich.edi> (#4595)

Date:   Mon Jan 15 11:38:20 2018 -0200

Compilation failure with grpc.h

If cmake run with flag FLATBUFFERS_BUILD_GRPCTEST=ON
compilation fails.

Fix :
	-Fix argument list for overriden function in grpc.
	-Fix member function name called by FlatBufferBuilder from
	buf() to scratch_data()

include/flatbuffers/flatbuffers.h

@@ -370,11 +370,23 @@ class Allocator {
                                        size_t in_use_front) {
     assert(new_size > old_size);  // vector_downward only grows
     uint8_t *new_p = allocate(new_size);
+    memcpy_downward(old_p, old_size, new_p, new_size, in_use_back,
+                    in_use_front);
+    deallocate(old_p, old_size);
+    return new_p;
+  }
+
+ protected:
+  // Called by `reallocate_downward` to copy memory from `old_p` of `old_size`
+  // to `new_p` of `new_size`. Only memory of size `in_use_front` and
+  // `in_use_back` will be copied from the front and back of the old memory
+  // allocation.
+  void memcpy_downward(uint8_t *old_p, size_t old_size,
+                       uint8_t *new_p, size_t new_size,
+                       size_t in_use_back, size_t in_use_front) {
     memcpy(new_p + new_size - in_use_back, old_p + old_size - in_use_back,
            in_use_back);
     memcpy(new_p, old_p, in_use_front);
-    deallocate(old_p, old_size);
-    return new_p;
   }
 };
 

include/flatbuffers/grpc.h

@@ -104,14 +104,16 @@ class SliceAllocator : public Allocator {
   }
 
   virtual uint8_t *reallocate_downward(uint8_t *old_p, size_t old_size,
-                                       size_t new_size) override {
+                                       size_t new_size, size_t in_use_back,
+                                       size_t in_use_front) override {
     assert(old_p == GRPC_SLICE_START_PTR(slice_));
     assert(old_size == GRPC_SLICE_LENGTH(slice_));
     assert(new_size > old_size);
     grpc_slice old_slice = slice_;
     grpc_slice new_slice = grpc_slice_malloc(new_size);
     uint8_t *new_p = GRPC_SLICE_START_PTR(new_slice);
-    memcpy(new_p + (new_size - old_size), old_p, old_size);
+    memcpy_downward(old_p, old_size, new_p, new_size, in_use_back,
+                    in_use_front);
     slice_ = new_slice;
     grpc_slice_unref(old_slice);
     return new_p;
@@ -155,7 +157,7 @@ class MessageBuilder : private detail::SliceAllocatorMember,
   // flatbuffers-encoded region and wraps it in a `Message<T>` to handle buffer
   // ownership.
   template<class T> Message<T> GetMessage() {
-    auto buf_data = buf_.buf();       // pointer to memory
+    auto buf_data = buf_.scratch_data();       // pointer to memory
     auto buf_size = buf_.capacity();  // size of memory
     auto msg_data = buf_.data();      // pointer to msg
     auto msg_size = buf_.size();      // size of msg