1 files changed, 159 insertions, 0 deletions
diff --git a/mozglue/misc/ConditionVariable_posix.cpp b/mozglue/misc/ConditionVariable_posix.cpp
new file mode 100644
index 0000000000..5c98560551
--- /dev/null
+++ b/mozglue/misc/ConditionVariable_posix.cpp
@@ -0,0 +1,159 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/Assertions.h"
+#include "mozilla/CheckedInt.h"
+
+#include <errno.h>
+#include <pthread.h>
+#include <time.h>
+
+#include "mozilla/PlatformConditionVariable.h"
+#include "mozilla/PlatformMutex.h"
+#include "MutexPlatformData_posix.h"
+
+using mozilla::CheckedInt;
+using mozilla::TimeDuration;
+
+static const long NanoSecPerSec = 1000000000;
+
+// Android 4.4 or earlier & macOS 10.12 has the clock functions, but not
+// pthread_condattr_setclock.
+#if defined(HAVE_CLOCK_MONOTONIC) && \
+    !(defined(__ANDROID__) && __ANDROID_API__ < 21) && !defined(__APPLE__)
+#  define CV_USE_CLOCK_API
+#endif
+
+#ifdef CV_USE_CLOCK_API
+// The C++ specification defines std::condition_variable::wait_for in terms of
+// std::chrono::steady_clock, which is closest to CLOCK_MONOTONIC.
+static const clockid_t WhichClock = CLOCK_MONOTONIC;
+
+// While timevaladd is widely available to work with timevals, the newer
+// timespec structure is largely lacking such conveniences. Thankfully, the
+// utilities available in MFBT make implementing our own quite easy.
+static void moz_timespecadd(struct timespec* lhs, struct timespec* rhs,
+                            struct timespec* result) {
+  // Add nanoseconds. This may wrap, but not above 2 billion.
+  MOZ_RELEASE_ASSERT(lhs->tv_nsec < NanoSecPerSec);
+  MOZ_RELEASE_ASSERT(rhs->tv_nsec < NanoSecPerSec);
+  result->tv_nsec = lhs->tv_nsec + rhs->tv_nsec;
+
+  // Add seconds, checking for overflow in the platform specific time_t type.
+  CheckedInt<time_t> sec = CheckedInt<time_t>(lhs->tv_sec) + rhs->tv_sec;
+
+  // If nanoseconds overflowed, carry the result over into seconds.
+  if (result->tv_nsec >= NanoSecPerSec) {
+    MOZ_RELEASE_ASSERT(result->tv_nsec < 2 * NanoSecPerSec);
+    result->tv_nsec -= NanoSecPerSec;
+    sec += 1;
+  }
+
+  // Extracting the value asserts that there was no overflow.
+  MOZ_RELEASE_ASSERT(sec.isValid());
+  result->tv_sec = sec.value();
+}
+#endif
+
+struct mozilla::detail::ConditionVariableImpl::PlatformData {
+  pthread_cond_t ptCond;
+};
+
+mozilla::detail::ConditionVariableImpl::ConditionVariableImpl() {
+  pthread_cond_t* ptCond = &platformData()->ptCond;
+
+#ifdef CV_USE_CLOCK_API
+  pthread_condattr_t attr;
+  int r0 = pthread_condattr_init(&attr);
+  MOZ_RELEASE_ASSERT(!r0);
+
+  int r1 = pthread_condattr_setclock(&attr, WhichClock);
+  MOZ_RELEASE_ASSERT(!r1);
+
+  int r2 = pthread_cond_init(ptCond, &attr);
+  MOZ_RELEASE_ASSERT(!r2);
+
+  int r3 = pthread_condattr_destroy(&attr);
+  MOZ_RELEASE_ASSERT(!r3);
+#else
+  int r = pthread_cond_init(ptCond, NULL);
+  MOZ_RELEASE_ASSERT(!r);
+#endif
+}
+
+mozilla::detail::ConditionVariableImpl::~ConditionVariableImpl() {
+  int r = pthread_cond_destroy(&platformData()->ptCond);
+  MOZ_RELEASE_ASSERT(r == 0);
+}
+
+void mozilla::detail::ConditionVariableImpl::notify_one() {
+  int r = pthread_cond_signal(&platformData()->ptCond);
+  MOZ_RELEASE_ASSERT(r == 0);
+}
+
+void mozilla::detail::ConditionVariableImpl::notify_all() {
+  int r = pthread_cond_broadcast(&platformData()->ptCond);
+  MOZ_RELEASE_ASSERT(r == 0);
+}
+
+void mozilla::detail::ConditionVariableImpl::wait(MutexImpl& lock) {
+  pthread_cond_t* ptCond = &platformData()->ptCond;
+  pthread_mutex_t* ptMutex = &lock.platformData()->ptMutex;
+
+  int r = pthread_cond_wait(ptCond, ptMutex);
+  MOZ_RELEASE_ASSERT(r == 0);
+}
+
+mozilla::CVStatus mozilla::detail::ConditionVariableImpl::wait_for(
+    MutexImpl& lock, const TimeDuration& a_rel_time) {
+  if (a_rel_time == TimeDuration::Forever()) {
+    wait(lock);
+    return CVStatus::NoTimeout;
+  }
+
+  pthread_cond_t* ptCond = &platformData()->ptCond;
+  pthread_mutex_t* ptMutex = &lock.platformData()->ptMutex;
+  int r;
+
+  // Clamp to 0, as time_t is unsigned.
+  TimeDuration rel_time = a_rel_time < TimeDuration::FromSeconds(0)
+                              ? TimeDuration::FromSeconds(0)
+                              : a_rel_time;
+
+  // Convert the duration to a timespec.
+  struct timespec rel_ts;
+  rel_ts.tv_sec = static_cast<time_t>(rel_time.ToSeconds());
+  rel_ts.tv_nsec =
+      static_cast<uint64_t>(rel_time.ToMicroseconds() * 1000.0) % NanoSecPerSec;
+
+#ifdef CV_USE_CLOCK_API
+  struct timespec now_ts;
+  r = clock_gettime(WhichClock, &now_ts);
+  MOZ_RELEASE_ASSERT(!r);
+
+  struct timespec abs_ts;
+  moz_timespecadd(&now_ts, &rel_ts, &abs_ts);
+
+  r = pthread_cond_timedwait(ptCond, ptMutex, &abs_ts);
+#else
+  // Our non-clock-supporting platforms, OS X and Android, do support waiting
+  // on a condition variable with a relative timeout.
+  r = pthread_cond_timedwait_relative_np(ptCond, ptMutex, &rel_ts);
+#endif
+
+  if (r == 0) {
+    return CVStatus::NoTimeout;
+  }
+  MOZ_RELEASE_ASSERT(r == ETIMEDOUT);
+  return CVStatus::Timeout;
+}
+
+mozilla::detail::ConditionVariableImpl::PlatformData*
+mozilla::detail::ConditionVariableImpl::platformData() {
+  static_assert(sizeof platformData_ >= sizeof(PlatformData),
+                "platformData_ is too small");
+  return reinterpret_cast<PlatformData*>(platformData_);
+}