1 files changed, 164 insertions, 0 deletions
diff --git a/ipc/glue/CrossProcessSemaphore_posix.cpp b/ipc/glue/CrossProcessSemaphore_posix.cpp
new file mode 100644
index 0000000000..3b32a897ee
--- /dev/null
+++ b/ipc/glue/CrossProcessSemaphore_posix.cpp
@@ -0,0 +1,164 @@
+/* -*- 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 "CrossProcessSemaphore.h"
+#include "mozilla/Unused.h"
+#include "nsDebug.h"
+#include "nsISupportsImpl.h"
+#include <errno.h>
+
+static const uint64_t kNsPerMs = 1000000;
+static const uint64_t kNsPerSec = 1000000000;
+
+namespace {
+
+struct SemaphoreData {
+  sem_t mSemaphore;
+  mozilla::Atomic<int32_t> mRefCount;
+  uint32_t mInitialValue;
+};
+
+}  // namespace
+
+namespace mozilla {
+
+/* static */
+CrossProcessSemaphore* CrossProcessSemaphore::Create(const char*,
+                                                     uint32_t aInitialValue) {
+  RefPtr<ipc::SharedMemoryBasic> sharedBuffer = new ipc::SharedMemoryBasic;
+  if (!sharedBuffer->Create(sizeof(SemaphoreData))) {
+    return nullptr;
+  }
+
+  if (!sharedBuffer->Map(sizeof(SemaphoreData))) {
+    return nullptr;
+  }
+
+  SemaphoreData* data = static_cast<SemaphoreData*>(sharedBuffer->memory());
+
+  if (!data) {
+    return nullptr;
+  }
+
+  if (sem_init(&data->mSemaphore, 1, aInitialValue)) {
+    return nullptr;
+  }
+
+  CrossProcessSemaphore* sem = new CrossProcessSemaphore;
+  sem->mSharedBuffer = sharedBuffer;
+  sem->mSemaphore = &data->mSemaphore;
+  sem->mRefCount = &data->mRefCount;
+  *sem->mRefCount = 1;
+
+  data->mInitialValue = aInitialValue;
+
+  return sem;
+}
+
+/* static */
+CrossProcessSemaphore* CrossProcessSemaphore::Create(
+    CrossProcessSemaphoreHandle aHandle) {
+  RefPtr<ipc::SharedMemoryBasic> sharedBuffer = new ipc::SharedMemoryBasic;
+
+  if (!sharedBuffer->IsHandleValid(aHandle)) {
+    return nullptr;
+  }
+
+  if (!sharedBuffer->SetHandle(std::move(aHandle),
+                               ipc::SharedMemory::RightsReadWrite)) {
+    return nullptr;
+  }
+
+  if (!sharedBuffer->Map(sizeof(SemaphoreData))) {
+    return nullptr;
+  }
+
+  sharedBuffer->CloseHandle();
+
+  SemaphoreData* data = static_cast<SemaphoreData*>(sharedBuffer->memory());
+
+  if (!data) {
+    return nullptr;
+  }
+
+  int32_t oldCount = data->mRefCount++;
+  if (oldCount == 0) {
+    // The other side has already let go of their CrossProcessSemaphore, so now
+    // mSemaphore is garbage. We need to re-initialize it.
+    if (sem_init(&data->mSemaphore, 1, data->mInitialValue)) {
+      data->mRefCount--;
+      return nullptr;
+    }
+  }
+
+  CrossProcessSemaphore* sem = new CrossProcessSemaphore;
+  sem->mSharedBuffer = sharedBuffer;
+  sem->mSemaphore = &data->mSemaphore;
+  sem->mRefCount = &data->mRefCount;
+  return sem;
+}
+
+CrossProcessSemaphore::CrossProcessSemaphore()
+    : mSemaphore(nullptr), mRefCount(nullptr) {
+  MOZ_COUNT_CTOR(CrossProcessSemaphore);
+}
+
+CrossProcessSemaphore::~CrossProcessSemaphore() {
+  int32_t oldCount = --(*mRefCount);
+
+  if (oldCount == 0) {
+    // Nothing can be done if the destroy fails so ignore return code.
+    Unused << sem_destroy(mSemaphore);
+  }
+
+  MOZ_COUNT_DTOR(CrossProcessSemaphore);
+}
+
+bool CrossProcessSemaphore::Wait(const Maybe<TimeDuration>& aWaitTime) {
+  MOZ_ASSERT(*mRefCount > 0,
+             "Attempting to wait on a semaphore with zero ref count");
+  int ret;
+  if (aWaitTime.isSome()) {
+    struct timespec ts;
+    if (clock_gettime(CLOCK_REALTIME, &ts) == -1) {
+      return false;
+    }
+
+    uint64_t ns = uint64_t(kNsPerMs * aWaitTime->ToMilliseconds()) + ts.tv_nsec;
+    ts.tv_sec += ns / kNsPerSec;
+    ts.tv_nsec = ns % kNsPerSec;
+
+    while ((ret = sem_timedwait(mSemaphore, &ts)) == -1 && errno == EINTR) {
+    }
+  } else {
+    while ((ret = sem_wait(mSemaphore)) == -1 && errno == EINTR) {
+    }
+  }
+  return ret == 0;
+}
+
+void CrossProcessSemaphore::Signal() {
+  MOZ_ASSERT(*mRefCount > 0,
+             "Attempting to signal a semaphore with zero ref count");
+  sem_post(mSemaphore);
+}
+
+CrossProcessSemaphoreHandle CrossProcessSemaphore::CloneHandle() {
+  CrossProcessSemaphoreHandle result = ipc::SharedMemoryBasic::NULLHandle();
+
+  if (mSharedBuffer) {
+    result = mSharedBuffer->CloneHandle();
+    if (!result) {
+      MOZ_CRASH();
+    }
+  }
+
+  return result;
+}
+
+void CrossProcessSemaphore::CloseHandle() { mSharedBuffer->CloseHandle(); }
+
+}  // namespace mozilla