1 files changed, 82 insertions, 0 deletions
diff --git a/third_party/libwebrtc/rtc_base/synchronization/yield_policy.cc b/third_party/libwebrtc/rtc_base/synchronization/yield_policy.cc
new file mode 100644
index 0000000000..d883d42bf4
--- /dev/null
+++ b/third_party/libwebrtc/rtc_base/synchronization/yield_policy.cc
@@ -0,0 +1,82 @@
+/*
+ *  Copyright 2019 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+#include "rtc_base/synchronization/yield_policy.h"
+
+#include "absl/base/attributes.h"
+#include "absl/base/config.h"
+#include "rtc_base/checks.h"
+#if !defined(ABSL_HAVE_THREAD_LOCAL) && defined(WEBRTC_POSIX)
+#include <pthread.h>
+#endif
+
+namespace rtc {
+namespace {
+
+#if defined(ABSL_HAVE_THREAD_LOCAL)
+
+ABSL_CONST_INIT thread_local YieldInterface* current_yield_policy = nullptr;
+
+YieldInterface* GetCurrentYieldPolicy() {
+  return current_yield_policy;
+}
+
+void SetCurrentYieldPolicy(YieldInterface* ptr) {
+  current_yield_policy = ptr;
+}
+
+#elif defined(WEBRTC_POSIX)
+
+// Emscripten does not support the C++11 thread_local keyword but does support
+// the pthread thread-local storage API.
+// https://github.com/emscripten-core/emscripten/issues/3502
+
+ABSL_CONST_INIT pthread_key_t g_current_yield_policy_tls = 0;
+
+void InitializeTls() {
+  RTC_CHECK_EQ(pthread_key_create(&g_current_yield_policy_tls, nullptr), 0);
+}
+
+pthread_key_t GetCurrentYieldPolicyTls() {
+  static pthread_once_t init_once = PTHREAD_ONCE_INIT;
+  RTC_CHECK_EQ(pthread_once(&init_once, &InitializeTls), 0);
+  return g_current_yield_policy_tls;
+}
+
+YieldInterface* GetCurrentYieldPolicy() {
+  return static_cast<YieldInterface*>(
+      pthread_getspecific(GetCurrentYieldPolicyTls()));
+}
+
+void SetCurrentYieldPolicy(YieldInterface* ptr) {
+  pthread_setspecific(GetCurrentYieldPolicyTls(), ptr);
+}
+
+#else
+#error Unsupported platform
+#endif
+
+}  // namespace
+
+ScopedYieldPolicy::ScopedYieldPolicy(YieldInterface* policy)
+    : previous_(GetCurrentYieldPolicy()) {
+  SetCurrentYieldPolicy(policy);
+}
+
+ScopedYieldPolicy::~ScopedYieldPolicy() {
+  SetCurrentYieldPolicy(previous_);
+}
+
+void ScopedYieldPolicy::YieldExecution() {
+  YieldInterface* current = GetCurrentYieldPolicy();
+  if (current)
+    current->YieldExecution();
+}
+
+}  // namespace rtc