Built motion from commit 6a09e18b.|2.6.11

[motion2.git] / legacy-libs / grpc / deps / grpc / src / core / lib / backoff / backoff.cc

diff --git a/legacy-libs/grpc/deps/grpc/src/core/lib/backoff/backoff.cc b/legacy-libs/grpc/deps/grpc/src/core/lib/backoff/backoff.cc
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+++ b/legacy-libs/grpc/deps/grpc/src/core/lib/backoff/backoff.cc
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+/*
+ *
+ * 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.
+ *
+ */
+
+#include <grpc/support/port_platform.h>
+
+#include "src/core/lib/backoff/backoff.h"
+
+#include <algorithm>
+
+#include "src/core/lib/gpr/useful.h"
+
+namespace grpc_core {
+
+namespace {
+
+/* Generate a random number between 0 and 1. We roll our own RNG because seeding
+ * rand() modifies a global variable we have no control over. */
+double generate_uniform_random_number(uint32_t* rng_state) {
+  constexpr uint32_t two_raise_31 = uint32_t(1) << 31;
+  *rng_state = (1103515245 * *rng_state + 12345) % two_raise_31;
+  return *rng_state / static_cast<double>(two_raise_31);
+}
+
+double generate_uniform_random_number_between(uint32_t* rng_state, double a,
+                                              double b) {
+  if (a == b) return a;
+  if (a > b) GPR_SWAP(double, a, b);  // make sure a < b
+  const double range = b - a;
+  return a + generate_uniform_random_number(rng_state) * range;
+}
+
+}  // namespace
+
+BackOff::BackOff(const Options& options)
+    : options_(options),
+      rng_state_(static_cast<uint32_t>(gpr_now(GPR_CLOCK_REALTIME).tv_nsec)) {
+  Reset();
+}
+
+grpc_millis BackOff::NextAttemptTime() {
+  if (initial_) {
+    initial_ = false;
+    return current_backoff_ + grpc_core::ExecCtx::Get()->Now();
+  }
+  current_backoff_ = static_cast<grpc_millis>(
+      std::min(current_backoff_ * options_.multiplier(),
+               static_cast<double>(options_.max_backoff())));
+  const double jitter = generate_uniform_random_number_between(
+      &rng_state_, -options_.jitter() * current_backoff_,
+      options_.jitter() * current_backoff_);
+  const grpc_millis next_timeout =
+      static_cast<grpc_millis>(current_backoff_ + jitter);
+  return next_timeout + grpc_core::ExecCtx::Get()->Now();
+}
+
+void BackOff::Reset() {
+  current_backoff_ = options_.initial_backoff();
+  initial_ = true;
+}
+
+void BackOff::SetRandomSeed(uint32_t seed) { rng_state_ = seed; }
+
+}  // namespace grpc_core