Revert "Revert "Metadata handling rewrite""

This reverts commit 5e01e2ac977655aa074faf7fde0a74298f5e4c55.

3 files changed, 21 insertions, 8 deletions

diff --git a/src/cpp/client/channel_cc.cc b/src/cpp/client/channel_cc.cc
index 357d8317ad..c985183ae7 100644
--- a/src/cpp/client/channel_cc.cc
+++ b/src/cpp/client/channel_cc.cc
@@ -107,10 +107,20 @@ Call Channel::CreateCall(const RpcMethod& method, ClientContext* context,
     } else if (!host_.empty()) {
       host_str = host_.c_str();
     }
-    c_call = grpc_channel_create_call(c_channel_, context->propagate_from_call_,
-                                      context->propagation_options_.c_bitmask(),
-                                      cq->cq(), method.name(), host_str,
-                                      context->raw_deadline(), nullptr);
+    grpc_slice method_slice = SliceFromCopiedString(method.name());
+    grpc_slice host_slice;
+    if (host_str != nullptr) {
+      host_slice = SliceFromCopiedString(host_str);
+    }
+    c_call = grpc_channel_create_call(
+        c_channel_, context->propagate_from_call_,
+        context->propagation_options_.c_bitmask(), cq->cq(), method_slice,
+        host_str == nullptr ? nullptr : &host_slice, context->raw_deadline(),
+        nullptr);
+    grpc_slice_unref(method_slice);
+    if (host_str != nullptr) {
+      grpc_slice_unref(host_slice);
+    }
   }
   grpc_census_call_set_context(c_call, context->census_context());
   context->set_call(c_call, shared_from_this());
diff --git a/src/cpp/client/secure_credentials.cc b/src/cpp/client/secure_credentials.cc
index 269c523bba..25f6bab7f2 100644
--- a/src/cpp/client/secure_credentials.cc
+++ b/src/cpp/client/secure_credentials.cc
@@ -206,15 +206,18 @@ void MetadataCredentialsPluginWrapper::InvokePlugin(
   std::vector<grpc_metadata> md;
   for (auto it = metadata.begin(); it != metadata.end(); ++it) {
     grpc_metadata md_entry;
-    md_entry.key = it->first.c_str();
-    md_entry.value = it->second.data();
-    md_entry.value_length = it->second.size();
+    md_entry.key = SliceFromCopiedString(it->first);
+    md_entry.value = SliceFromCopiedString(it->second);
     md_entry.flags = 0;
     md.push_back(md_entry);
   }
   cb(user_data, md.empty() ? nullptr : &md[0], md.size(),
      static_cast<grpc_status_code>(status.error_code()),
      status.error_message().c_str());
+  for (auto it = md.begin(); it != md.end(); ++it) {
+    grpc_slice_unref(it->key);
+    grpc_slice_unref(it->value);
+  }
 }
 
 MetadataCredentialsPluginWrapper::MetadataCredentialsPluginWrapper(
diff --git a/src/cpp/client/secure_credentials.h b/src/cpp/client/secure_credentials.h
index 281db17e98..713654ad5b 100644
--- a/src/cpp/client/secure_credentials.h
+++ b/src/cpp/client/secure_credentials.h
@@ -70,7 +70,7 @@ class SecureCallCredentials final : public CallCredentials {
   grpc_call_credentials* const c_creds_;
 };
 
-class MetadataCredentialsPluginWrapper final {
+class MetadataCredentialsPluginWrapper final : private GrpcLibraryCodegen {
  public:
   static void Destroy(void* wrapper);
   static void GetMetadata(void* wrapper, grpc_auth_metadata_context context,