--- /dev/null
+/*
+ *
+ * Copyright 2016 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_SECURITY_CREDENTIALS_PLUGIN_PLUGIN_CREDENTIALS_H
+#define GRPC_CORE_LIB_SECURITY_CREDENTIALS_PLUGIN_PLUGIN_CREDENTIALS_H
+
+#include <grpc/support/port_platform.h>
+
+#include "src/core/lib/security/credentials/credentials.h"
+
+extern grpc_core::TraceFlag grpc_plugin_credentials_trace;
+
+// This type is forward declared as a C struct and we cannot define it as a
+// class. Otherwise, compiler will complain about type mismatch due to
+// -Wmismatched-tags.
+struct grpc_plugin_credentials final : public grpc_call_credentials {
+ public:
+ struct pending_request {
+ bool cancelled;
+ struct grpc_plugin_credentials* creds;
+ grpc_credentials_mdelem_array* md_array;
+ grpc_closure* on_request_metadata;
+ struct pending_request* prev;
+ struct pending_request* next;
+ };
+
+ explicit grpc_plugin_credentials(grpc_metadata_credentials_plugin plugin);
+ ~grpc_plugin_credentials() override;
+
+ bool get_request_metadata(grpc_polling_entity* pollent,
+ grpc_auth_metadata_context context,
+ grpc_credentials_mdelem_array* md_array,
+ grpc_closure* on_request_metadata,
+ grpc_error** error) override;
+
+ void cancel_get_request_metadata(grpc_credentials_mdelem_array* md_array,
+ grpc_error* error) override;
+
+ // Checks if the request has been cancelled.
+ // If not, removes it from the pending list, so that it cannot be
+ // cancelled out from under us.
+ // When this returns, r->cancelled indicates whether the request was
+ // cancelled before completion.
+ void pending_request_complete(pending_request* r);
+
+ private:
+ void pending_request_remove_locked(pending_request* pending_request);
+
+ grpc_metadata_credentials_plugin plugin_;
+ gpr_mu mu_;
+ pending_request* pending_requests_ = nullptr;
+};
+
+#endif /* GRPC_CORE_LIB_SECURITY_CREDENTIALS_PLUGIN_PLUGIN_CREDENTIALS_H */