1 files changed, 104 insertions, 0 deletions
diff --git a/absl/strings/internal/cordz_functions.cc b/absl/strings/internal/cordz_functions.cc
new file mode 100644
index 00000000..6ad864f1
--- /dev/null
+++ b/absl/strings/internal/cordz_functions.cc
@@ -0,0 +1,104 @@
+// Copyright 2019 The Abseil 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
+//
+//      https://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 "absl/strings/internal/cordz_functions.h"
+
+#include <atomic>
+#include <cmath>
+#include <limits>
+#include <random>
+
+#include "absl/base/attributes.h"
+#include "absl/base/config.h"
+#include "absl/base/internal/exponential_biased.h"
+#include "absl/base/internal/raw_logging.h"
+
+// TODO(b/162942788): weak 'cordz_disabled' value.
+// A strong version is in the 'cordz_disabled_hack_for_odr' library which can
+// be linked in to disable cordz at compile time.
+extern "C" {
+bool absl_internal_cordz_disabled ABSL_ATTRIBUTE_WEAK = false;
+}
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace cord_internal {
+namespace {
+
+// The average interval until the next sample. A value of 0 disables profiling
+// while a value of 1 will profile all Cords.
+std::atomic<int> g_cordz_mean_interval(50000);
+
+}  // namespace
+
+#ifdef ABSL_INTERNAL_CORDZ_ENABLED
+
+ABSL_CONST_INIT thread_local int64_t cordz_next_sample = 0;
+
+// kIntervalIfDisabled is the number of profile-eligible events need to occur
+// before the code will confirm that cordz is still disabled.
+constexpr int64_t kIntervalIfDisabled = 1 << 16;
+
+ABSL_ATTRIBUTE_NOINLINE bool cordz_should_profile_slow() {
+  // TODO(b/162942788): check if profiling is disabled at compile time.
+  if (absl_internal_cordz_disabled) {
+    ABSL_RAW_LOG(WARNING, "Cordz info disabled at compile time");
+    // We are permanently disabled: set counter to highest possible value.
+    cordz_next_sample = std::numeric_limits<int64_t>::max();
+    return false;
+  }
+
+  thread_local absl::base_internal::ExponentialBiased
+      exponential_biased_generator;
+  int32_t mean_interval = get_cordz_mean_interval();
+
+  // Check if we disabled profiling. If so, set the next sample to a "large"
+  // number to minimize the overhead of the should_profile codepath.
+  if (mean_interval <= 0) {
+    cordz_next_sample = kIntervalIfDisabled;
+    return false;
+  }
+
+  // Check if we're always sampling.
+  if (mean_interval == 1) {
+    cordz_next_sample = 1;
+    return true;
+  }
+
+  if (cordz_next_sample <= 0) {
+    cordz_next_sample = exponential_biased_generator.GetStride(mean_interval);
+    return true;
+  }
+
+  --cordz_next_sample;
+  return false;
+}
+
+void cordz_set_next_sample_for_testing(int64_t next_sample) {
+  cordz_next_sample = next_sample;
+}
+
+#endif  // ABSL_INTERNAL_CORDZ_ENABLED
+
+int32_t get_cordz_mean_interval() {
+  return g_cordz_mean_interval.load(std::memory_order_acquire);
+}
+
+void set_cordz_mean_interval(int32_t mean_interval) {
+  g_cordz_mean_interval.store(mean_interval, std::memory_order_release);
+}
+
+}  // namespace cord_internal
+ABSL_NAMESPACE_END
+}  // namespace absl