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+/*
+ *
+ * Copyright 2015, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_EXT_CLIENT_CHANNEL_LB_POLICY_FACTORY_H
+#define GRPC_CORE_EXT_CLIENT_CHANNEL_LB_POLICY_FACTORY_H
+
+#include "src/core/ext/client_channel/client_channel_factory.h"
+#include "src/core/ext/client_channel/lb_policy.h"
+
+#include "src/core/lib/iomgr/exec_ctx.h"
+#include "src/core/lib/iomgr/resolve_address.h"
+
+typedef struct grpc_lb_policy_factory grpc_lb_policy_factory;
+typedef struct grpc_lb_policy_factory_vtable grpc_lb_policy_factory_vtable;
+
+struct grpc_lb_policy_factory {
+  const grpc_lb_policy_factory_vtable *vtable;
+};
+
+/** A resolved address alongside any LB related information associated with it.
+ * \a user_data, if not NULL, contains opaque data meant to be consumed by the
+ * gRPC LB policy. Note that no all LB policies support \a user_data as input.
+ * Those who don't will simply ignore it and will correspondingly return NULL in
+ * their namesake pick() output argument. */
+typedef struct grpc_lb_address {
+  grpc_resolved_address address;
+  bool is_balancer;
+  char *balancer_name; /* For secure naming. */
+  void *user_data;
+} grpc_lb_address;
+
+typedef struct grpc_lb_addresses {
+  size_t num_addresses;
+  grpc_lb_address *addresses;
+} grpc_lb_addresses;
+
+/** Returns a grpc_addresses struct with enough space for
+ * \a num_addresses addresses. */
+grpc_lb_addresses *grpc_lb_addresses_create(size_t num_addresses);
+
+/** Creates a copy of \a addresses.  If \a user_data_copy is not NULL,
+ * it will be invoked to copy the \a user_data field of each address. */
+grpc_lb_addresses *grpc_lb_addresses_copy(grpc_lb_addresses *addresses,
+                                          void *(*user_data_copy)(void *));
+
+/** Sets the value of the address at index \a index of \a addresses.
+ * \a address is a socket address of length \a address_len.
+ * Takes ownership of \a balancer_name. */
+void grpc_lb_addresses_set_address(grpc_lb_addresses *addresses, size_t index,
+                                   void *address, size_t address_len,
+                                   bool is_balancer, char *balancer_name,
+                                   void *user_data);
+
+/** Destroys \a addresses.  If \a user_data_destroy is not NULL, it will
+ * be invoked to destroy the \a user_data field of each address. */
+void grpc_lb_addresses_destroy(grpc_lb_addresses *addresses,
+                               void (*user_data_destroy)(void *));
+
+/** Arguments passed to LB policies. */
+/* TODO(roth, ctiller): Consider replacing this struct with
+   grpc_channel_args.  See comment in resolver_result.h for details. */
+typedef struct grpc_lb_policy_args {
+  const char *server_name;
+  grpc_lb_addresses *addresses;
+  grpc_client_channel_factory *client_channel_factory;
+  /* Can be used to pass implementation-specific parameters to the LB policy. */
+  grpc_channel_args *additional_args;
+} grpc_lb_policy_args;
+
+struct grpc_lb_policy_factory_vtable {
+  void (*ref)(grpc_lb_policy_factory *factory);
+  void (*unref)(grpc_lb_policy_factory *factory);
+
+  /** Implementation of grpc_lb_policy_factory_create_lb_policy */
+  grpc_lb_policy *(*create_lb_policy)(grpc_exec_ctx *exec_ctx,
+                                      grpc_lb_policy_factory *factory,
+                                      grpc_lb_policy_args *args);
+
+  /** Name for the LB policy this factory implements */
+  const char *name;
+};
+
+void grpc_lb_policy_factory_ref(grpc_lb_policy_factory *factory);
+void grpc_lb_policy_factory_unref(grpc_lb_policy_factory *factory);
+
+/** Create a lb_policy instance. */
+grpc_lb_policy *grpc_lb_policy_factory_create_lb_policy(
+    grpc_exec_ctx *exec_ctx, grpc_lb_policy_factory *factory,
+    grpc_lb_policy_args *args);
+
+#endif /* GRPC_CORE_EXT_CLIENT_CHANNEL_LB_POLICY_FACTORY_H */