Initial work

external/android-emugl/shared/emugl/common/lazy_instance.cpp

@@ -0,0 +1,101 @@
+// Copyright (C) 2014 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "emugl/common/lazy_instance.h"
+
+#ifdef _WIN32
+#  define WIN32_LEAN_AND_MEAN 1
+#  include <windows.h>
+#else
+#  include <sched.h>
+#endif
+
+namespace emugl {
+namespace internal {
+
+typedef LazyInstanceState::AtomicType AtomicType;
+
+#if defined(__GNUC__)
+static inline void compilerBarrier() {
+    __asm__ __volatile__ ("" : : : "memory");
+}
+#else
+#error "Your compiler is not supported"
+#endif
+
+#if defined(__i386__) || defined(__x86_64__) || defined(__arm__)
+#  define acquireBarrier() compilerBarrier()
+#  define releaseBarrier() compilerBarrier()
+#else
+#  error "Your CPU is not supported"
+#endif
+
+static inline AtomicType loadAcquire(AtomicType volatile* ptr) {
+    AtomicType ret = *ptr;
+    acquireBarrier();
+    return ret;
+}
+
+static inline void storeRelease(AtomicType volatile* ptr, AtomicType value) {
+    releaseBarrier();
+    *ptr = value;
+}
+
+static int atomicCompareAndSwap(AtomicType volatile* ptr,
+                                int expected,
+                                int value) {
+#ifdef _WIN32
+    return InterlockedCompareExchange(ptr, value, expected);
+#elif defined(__GNUC__)
+    return __sync_val_compare_and_swap(ptr, expected, value);
+#else
+#error "Your compiler is not supported"
+#endif
+}
+
+static void yieldThread() {
+#ifdef _WIN32
+    ::Sleep(0);
+#else
+    sched_yield();
+#endif
+}
+
+bool LazyInstanceState::inInitState() {
+    return loadAcquire(&mState) == STATE_INIT;
+}
+
+bool LazyInstanceState::needConstruction() {
+    AtomicType state = loadAcquire(&mState);
+    if (mState == STATE_DONE)
+        return false;
+
+    state = atomicCompareAndSwap(&mState, STATE_INIT, STATE_CONSTRUCTING);
+    if (state == STATE_INIT)
+        return true;
+
+    do {
+        yieldThread();
+        state = loadAcquire(&mState);
+    } while (state != STATE_DONE);
+
+    return false;
+}
+
+void LazyInstanceState::doneConstructing() {
+    storeRelease(&mState, STATE_DONE);
+}
+
+}  // namespace internal
+}  // namespace emugl