1 files changed, 103 insertions, 0 deletions
diff --git a/toolkit/mozapps/defaultagent/WindowsMutex.cpp b/toolkit/mozapps/defaultagent/WindowsMutex.cpp
new file mode 100644
index 0000000000..804c3e6d75
--- /dev/null
+++ b/toolkit/mozapps/defaultagent/WindowsMutex.cpp
@@ -0,0 +1,103 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* 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/Logging.h"
+
+#include "WindowsMutex.h"
+
+namespace mozilla::default_agent {
+
+using mozilla::LogLevel;
+
+static LazyLogModule gWindowsMutexLog("WindowsMutex");
+
+NS_IMPL_ISUPPORTS(WindowsMutexFactory, nsIWindowsMutexFactory)
+
+NS_IMETHODIMP
+WindowsMutexFactory::CreateMutex(const nsAString& aName,
+                                 nsIWindowsMutex** aWindowsMutex) {
+  nsAutoHandle mutex;
+  auto name = PromiseFlatString(aName);
+
+  mutex.own(CreateMutexW(nullptr, FALSE, name.get()));
+  if (mutex.get() == nullptr) {
+    MOZ_LOG(gWindowsMutexLog, LogLevel::Error,
+            ("Couldn't open mutex \"%s\": %#lX",
+             NS_ConvertUTF16toUTF8(name).get(), GetLastError()));
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  RefPtr<WindowsMutex> nsMutex = new WindowsMutex(name, mutex);
+  nsMutex.forget(aWindowsMutex);
+  return NS_OK;
+}
+
+WindowsMutex::WindowsMutex(const nsString& aName, nsAutoHandle& aMutex)
+    : mName(NS_ConvertUTF16toUTF8(aName)), mLocked(false) {
+  mMutex.steal(aMutex);
+}
+
+WindowsMutex::~WindowsMutex() {
+  Unlock();
+  // nsAutoHandle will take care of closing the mutex's handle.
+}
+
+NS_IMPL_ISUPPORTS(WindowsMutex, nsIWindowsMutex)
+
+NS_IMETHODIMP
+WindowsMutex::TryLock() {
+  // This object may be used on the main thread, so don't wait if it's
+  // not signaled.
+  DWORD mutexStatus = WaitForSingleObject(mMutex.get(), 0);
+  if (mutexStatus == WAIT_OBJECT_0) {
+    mLocked = true;
+  } else if (mutexStatus == WAIT_TIMEOUT) {
+    MOZ_LOG(gWindowsMutexLog, LogLevel::Warning,
+            ("Timed out waiting for mutex \"%s\"", mName.get()));
+  } else if (mutexStatus == WAIT_ABANDONED) {
+    // This status code means that we are supposed to check our data for
+    // consistency as the last locking process didn't signal intentional
+    // unlocking which might indicate it crashed mid-operation. Current uses of
+    // this `WindowsMutex` don't need to worry about corruption of the locked
+    // object, if needed the `nsIWindowsMutex` interface should be extended.
+    MOZ_LOG(gWindowsMutexLog, LogLevel::Warning,
+            ("Found abandoned mutex \"%s\". Continuing...", mName.get()));
+    mLocked = true;
+  } else {
+    // The only other documented status code is WAIT_FAILED. In the case that
+    // we somehow get some other code, that is also an error.
+    MOZ_LOG(gWindowsMutexLog, LogLevel::Error,
+            ("Failed to wait on mutex: mName: %s, error %#lX", mName.get(),
+             GetLastError()));
+  }
+  return mLocked ? NS_OK : NS_ERROR_NOT_AVAILABLE;
+}
+
+NS_IMETHODIMP
+WindowsMutex::IsLocked(bool* aLocked) {
+  *aLocked = mLocked;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+WindowsMutex::Unlock() {
+  nsresult rv = NS_OK;
+
+  if (mLocked) {
+    BOOL success = ReleaseMutex(mMutex.get());
+    if (!success) {
+      MOZ_LOG(gWindowsMutexLog, LogLevel::Error,
+              ("Failed to release mutex \"%s\"", mName.get()));
+      rv = NS_ERROR_UNEXPECTED;
+    }
+
+    mLocked = false;
+  }
+
+  return rv;
+}
+
+}  // namespace mozilla::default_agent