1 files changed, 259 insertions, 0 deletions
diff --git a/src/core/client_config/subchannel_index.c b/src/core/client_config/subchannel_index.c
new file mode 100644
index 0000000000..f78a7fd588
--- /dev/null
+++ b/src/core/client_config/subchannel_index.c
@@ -0,0 +1,259 @@
+//
+//
+// Copyright 2016, 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.
+//
+//
+
+#include "src/core/client_config/subchannel_index.h"
+
+#include <stdbool.h>
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/avl.h>
+#include <grpc/support/tls.h>
+
+#include "src/core/channel/channel_args.h"
+
+// a map of subchannel_key --> subchannel, used for detecting connections
+// to the same destination in order to share them
+static gpr_avl g_subchannel_index;
+
+static gpr_mu g_mu;
+
+struct grpc_subchannel_key {
+  grpc_connector *connector;
+  grpc_subchannel_args args;
+};
+
+GPR_TLS_DECL(subchannel_index_exec_ctx);
+
+static void enter_ctx(grpc_exec_ctx *exec_ctx) {
+  GPR_ASSERT(gpr_tls_get(&subchannel_index_exec_ctx) == 0);
+  gpr_tls_set(&subchannel_index_exec_ctx, (intptr_t)exec_ctx);
+}
+
+static void leave_ctx(grpc_exec_ctx *exec_ctx) {
+  GPR_ASSERT(gpr_tls_get(&subchannel_index_exec_ctx) == (intptr_t)exec_ctx);
+  gpr_tls_set(&subchannel_index_exec_ctx, 0);
+}
+
+static grpc_exec_ctx *current_ctx() {
+  grpc_exec_ctx *c = (grpc_exec_ctx *)gpr_tls_get(&subchannel_index_exec_ctx);
+  GPR_ASSERT(c != NULL);
+  return c;
+}
+
+static grpc_subchannel_key *create_key(
+    grpc_connector *connector, grpc_subchannel_args *args,
+    grpc_channel_args *(*copy_channel_args)(const grpc_channel_args *args)) {
+  grpc_subchannel_key *k = gpr_malloc(sizeof(*k));
+  k->connector = grpc_connector_ref(connector);
+  k->args.filter_count = args->filter_count;
+  k->args.filters = gpr_malloc(sizeof(*k->args.filters) * k->args.filter_count);
+  memcpy((grpc_channel_filter *)k->args.filters, args->filters,
+         sizeof(*k->args.filters) * k->args.filter_count);
+  k->args.addr_len = args->addr_len;
+  k->args.addr = gpr_malloc(args->addr_len);
+  memcpy(k->args.addr, args->addr, k->args.addr_len);
+  k->args.args = copy_channel_args(args->args);
+  return k;
+}
+
+grpc_subchannel_key *grpc_subchannel_key_create(grpc_connector *connector,
+                                                grpc_subchannel_args *args) {
+  return create_key(connector, args, grpc_channel_args_normalize);
+}
+
+static grpc_subchannel_key *subchannel_key_copy(grpc_subchannel_key *k) {
+  return create_key(k->connector, &k->args, grpc_channel_args_copy);
+}
+
+static int subchannel_key_compare(grpc_subchannel_key *a,
+                                  grpc_subchannel_key *b) {
+  int c = GPR_ICMP(a->connector, b->connector);
+  if (c != 0) return c;
+  c = GPR_ICMP(a->args.addr_len, b->args.addr_len);
+  if (c != 0) return c;
+  c = GPR_ICMP(a->args.filter_count, b->args.filter_count);
+  if (c != 0) return c;
+  c = memcmp(a->args.addr, b->args.addr, a->args.addr_len);
+  if (c != 0) return c;
+  c = memcmp(a->args.filters, b->args.filters,
+             a->args.filter_count * sizeof(*a->args.filters));
+  return grpc_channel_args_compare(a->args.args, b->args.args);
+}
+
+void grpc_subchannel_key_destroy(grpc_exec_ctx *exec_ctx,
+                                 grpc_subchannel_key *k) {
+  grpc_connector_unref(exec_ctx, k->connector);
+  gpr_free(k->args.addr);
+  gpr_free((grpc_channel_args *)k->args.filters);
+  grpc_channel_args_destroy((grpc_channel_args *)k->args.args);
+  gpr_free(k);
+}
+
+static void sck_avl_destroy(void *p) {
+  grpc_subchannel_key_destroy(current_ctx(), p);
+}
+
+static void *sck_avl_copy(void *p) { return subchannel_key_copy(p); }
+
+static long sck_avl_compare(void *a, void *b) {
+  return subchannel_key_compare(a, b);
+}
+
+static void scv_avl_destroy(void *p) {
+  GRPC_SUBCHANNEL_WEAK_UNREF(current_ctx(), p, "subchannel_index");
+}
+
+static void *scv_avl_copy(void *p) {
+  GRPC_SUBCHANNEL_WEAK_REF(p, "subchannel_index");
+  return p;
+}
+
+static const gpr_avl_vtable subchannel_avl_vtable = {
+    .destroy_key = sck_avl_destroy,
+    .copy_key = sck_avl_copy,
+    .compare_keys = sck_avl_compare,
+    .destroy_value = scv_avl_destroy,
+    .copy_value = scv_avl_copy};
+
+void grpc_subchannel_index_init(void) {
+  g_subchannel_index = gpr_avl_create(&subchannel_avl_vtable);
+  gpr_mu_init(&g_mu);
+}
+
+void grpc_subchannel_index_shutdown(void) {
+  gpr_mu_destroy(&g_mu);
+  gpr_avl_unref(g_subchannel_index);
+}
+
+grpc_subchannel *grpc_subchannel_index_find(grpc_exec_ctx *exec_ctx,
+                                            grpc_subchannel_key *key) {
+  enter_ctx(exec_ctx);
+
+  // Lock, and take a reference to the subchannel index.
+  // We don't need to do the search under a lock as avl's are immutable.
+  gpr_mu_lock(&g_mu);
+  gpr_avl index = gpr_avl_ref(g_subchannel_index);
+  gpr_mu_unlock(&g_mu);
+
+  grpc_subchannel *c =
+      GRPC_SUBCHANNEL_REF_FROM_WEAK_REF(gpr_avl_get(index, key), "index_find");
+  gpr_avl_unref(index);
+
+  leave_ctx(exec_ctx);
+  return c;
+}
+
+grpc_subchannel *grpc_subchannel_index_register(grpc_exec_ctx *exec_ctx,
+                                                grpc_subchannel_key *key,
+                                                grpc_subchannel *constructed) {
+  enter_ctx(exec_ctx);
+
+  grpc_subchannel *c = NULL;
+
+  while (c == NULL) {
+    // Compare and swap loop:
+    // - take a reference to the current index
+    gpr_mu_lock(&g_mu);
+    gpr_avl index = gpr_avl_ref(g_subchannel_index);
+    gpr_mu_unlock(&g_mu);
+
+    // - Check to see if a subchannel already exists
+    c = gpr_avl_get(index, key);
+    if (c != NULL) {
+      // yes -> we're done
+      GRPC_SUBCHANNEL_WEAK_UNREF(exec_ctx, constructed, "index_register");
+    } else {
+      // no -> update the avl and compare/swap
+      gpr_avl updated =
+          gpr_avl_add(gpr_avl_ref(index), subchannel_key_copy(key),
+                      GRPC_SUBCHANNEL_WEAK_REF(constructed, "index_register"));
+
+      // it may happen (but it's expected to be unlikely)
+      // that some other thread has changed the index:
+      // compare/swap here to check that, and retry as necessary
+      gpr_mu_lock(&g_mu);
+      if (index.root == g_subchannel_index.root) {
+        GPR_SWAP(gpr_avl, updated, g_subchannel_index);
+        c = constructed;
+      }
+      gpr_mu_unlock(&g_mu);
+
+      gpr_avl_unref(updated);
+    }
+    gpr_avl_unref(index);
+  }
+
+  leave_ctx(exec_ctx);
+
+  return c;
+}
+
+void grpc_subchannel_index_unregister(grpc_exec_ctx *exec_ctx,
+                                      grpc_subchannel_key *key,
+                                      grpc_subchannel *constructed) {
+  enter_ctx(exec_ctx);
+
+  bool done = false;
+  while (!done) {
+    // Compare and swap loop:
+    // - take a reference to the current index
+    gpr_mu_lock(&g_mu);
+    gpr_avl index = gpr_avl_ref(g_subchannel_index);
+    gpr_mu_unlock(&g_mu);
+
+    // Check to see if this key still refers to the previously
+    // registered subchannel
+    grpc_subchannel *c = gpr_avl_get(index, key);
+    if (c != constructed) {
+      gpr_avl_unref(index);
+      break;
+    }
+
+    // compare and swap the update (some other thread may have
+    // mutated the index behind us)
+    gpr_avl updated = gpr_avl_remove(gpr_avl_ref(index), key);
+
+    gpr_mu_lock(&g_mu);
+    if (index.root == g_subchannel_index.root) {
+      GPR_SWAP(gpr_avl, updated, g_subchannel_index);
+      done = true;
+    }
+    gpr_mu_unlock(&g_mu);
+
+    gpr_avl_unref(updated);
+    gpr_avl_unref(index);
+  }
+
+  leave_ctx(exec_ctx);
+}