1 files changed, 98 insertions, 0 deletions
diff --git a/mozglue/misc/ConditionVariable_windows.cpp b/mozglue/misc/ConditionVariable_windows.cpp
new file mode 100644
index 0000000000..0c0151f1d3
--- /dev/null
+++ b/mozglue/misc/ConditionVariable_windows.cpp
@@ -0,0 +1,98 @@
+/* -*- 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 <float.h>
+#include <intrin.h>
+#include <stdlib.h>
+#include <windows.h>
+
+#include "mozilla/PlatformConditionVariable.h"
+#include "mozilla/PlatformMutex.h"
+#include "MutexPlatformData_windows.h"
+
+// Some versions of the Windows SDK have a bug where some interlocked functions
+// are not redefined as compiler intrinsics. Fix that for the interlocked
+// functions that are used in this file.
+#if defined(_MSC_VER) && !defined(InterlockedExchangeAdd)
+#  define InterlockedExchangeAdd(addend, value) \
+    _InterlockedExchangeAdd((volatile long*)(addend), (long)(value))
+#endif
+
+#if defined(_MSC_VER) && !defined(InterlockedIncrement)
+#  define InterlockedIncrement(addend) \
+    _InterlockedIncrement((volatile long*)(addend))
+#endif
+
+// Wrapper for native condition variable APIs.
+struct mozilla::detail::ConditionVariableImpl::PlatformData {
+  CONDITION_VARIABLE cv_;
+};
+
+mozilla::detail::ConditionVariableImpl::ConditionVariableImpl() {
+  InitializeConditionVariable(&platformData()->cv_);
+}
+
+void mozilla::detail::ConditionVariableImpl::notify_one() {
+  WakeConditionVariable(&platformData()->cv_);
+}
+
+void mozilla::detail::ConditionVariableImpl::notify_all() {
+  WakeAllConditionVariable(&platformData()->cv_);
+}
+
+void mozilla::detail::ConditionVariableImpl::wait(MutexImpl& lock) {
+  SRWLOCK* srwlock = &lock.platformData()->lock;
+  bool r =
+      SleepConditionVariableSRW(&platformData()->cv_, srwlock, INFINITE, 0);
+  MOZ_RELEASE_ASSERT(r);
+}
+
+mozilla::CVStatus mozilla::detail::ConditionVariableImpl::wait_for(
+    MutexImpl& lock, const mozilla::TimeDuration& rel_time) {
+  if (rel_time == mozilla::TimeDuration::Forever()) {
+    wait(lock);
+    return CVStatus::NoTimeout;
+  }
+
+  SRWLOCK* srwlock = &lock.platformData()->lock;
+
+  // Note that DWORD is unsigned, so we have to be careful to clamp at 0. If
+  // rel_time is Forever, then ToMilliseconds is +inf, which evaluates as
+  // greater than UINT32_MAX, resulting in the correct INFINITE wait. We also
+  // don't want to round sub-millisecond waits to 0, as that wastes energy (see
+  // bug 1437167 comment 6), so we instead round submillisecond waits to 1ms.
+  double msecd = rel_time.ToMilliseconds();
+  DWORD msec;
+  if (msecd < 0.0) {
+    msec = 0;
+  } else if (msecd > UINT32_MAX) {
+    msec = INFINITE;
+  } else {
+    msec = static_cast<DWORD>(msecd);
+    // Round submillisecond waits to 1ms.
+    if (msec == 0 && !rel_time.IsZero()) {
+      msec = 1;
+    }
+  }
+
+  BOOL r = SleepConditionVariableSRW(&platformData()->cv_, srwlock, msec, 0);
+  if (r) return CVStatus::NoTimeout;
+  MOZ_RELEASE_ASSERT(GetLastError() == ERROR_TIMEOUT);
+  return CVStatus::Timeout;
+}
+
+mozilla::detail::ConditionVariableImpl::~ConditionVariableImpl() {
+  // Native condition variables don't require cleanup.
+}
+
+inline mozilla::detail::ConditionVariableImpl::PlatformData*
+mozilla::detail::ConditionVariableImpl::platformData() {
+  static_assert(sizeof platformData_ >= sizeof(PlatformData),
+                "platformData_ is too small");
+  return reinterpret_cast<PlatformData*>(platformData_);
+}