1 files changed, 141 insertions, 0 deletions
diff --git a/core/java/android/os/ConditionVariable.java b/core/java/android/os/ConditionVariable.java
new file mode 100644
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+++ b/core/java/android/os/ConditionVariable.java
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+/*
+ * Copyright (C) 2006 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.
+ */
+
+package android.os;
+
+/**
+ * Class that implements the condition variable locking paradigm.
+ *
+ * <p>
+ * This differs from the built-in java.lang.Object wait() and notify()
+ * in that this class contains the condition to wait on itself.  That means
+ * open(), close() and block() are sticky.  If open() is called before block(),
+ * block() will not block, and instead return immediately.
+ *
+ * <p>
+ * This class uses itself is at the object to wait on, so if you wait()
+ * or notify() on a ConditionVariable, the results are undefined.
+ */
+public class ConditionVariable
+{
+    private volatile boolean mCondition;
+
+    /**
+     * Create the ConditionVariable in the default closed state.
+     */
+    public ConditionVariable()
+    {
+        mCondition = false;
+    }
+
+    /**
+     * Create the ConditionVariable with the given state.
+     * 
+     * <p>
+     * Pass true for opened and false for closed.
+     */
+    public ConditionVariable(boolean state)
+    {
+        mCondition = state;
+    }
+
+    /**
+     * Open the condition, and release all threads that are blocked.
+     *
+     * <p>
+     * Any threads that later approach block() will not block unless close()
+     * is called.
+     */
+    public void open()
+    {
+        synchronized (this) {
+            boolean old = mCondition;
+            mCondition = true;
+            if (!old) {
+                this.notifyAll();
+            }
+        }
+    }
+
+    /**
+     * Reset the condition to the closed state.
+     *
+     * <p>
+     * Any threads that call block() will block until someone calls open.
+     */
+    public void close()
+    {
+        synchronized (this) {
+            mCondition = false;
+        }
+    }
+
+    /**
+     * Block the current thread until the condition is opened.
+     *
+     * <p>
+     * If the condition is already opened, return immediately.
+     */
+    public void block()
+    {
+        synchronized (this) {
+            while (!mCondition) {
+                try {
+                    this.wait();
+                }
+                catch (InterruptedException e) {
+                }
+            }
+        }
+    }
+
+    /**
+     * Block the current thread until the condition is opened or until
+     * timeout milliseconds have passed.
+     *
+     * <p>
+     * If the condition is already opened, return immediately.
+     *
+     * @param timeout the minimum time to wait in milliseconds.
+     *
+     * @return true if the condition was opened, false if the call returns
+     * because of the timeout.
+     */
+    public boolean block(long timeout)
+    {
+        // Object.wait(0) means wait forever, to mimic this, we just
+        // call the other block() method in that case.  It simplifies
+        // this code for the common case.
+        if (timeout != 0) {
+            synchronized (this) {
+                long now = System.currentTimeMillis();
+                long end = now + timeout;
+                while (!mCondition && now < end) {
+                    try {
+                        this.wait(end-now);
+                    }
+                    catch (InterruptedException e) {
+                    }
+                    now = System.currentTimeMillis();
+                }
+                return mCondition;
+            }
+        } else {
+            this.block();
+            return true;
+        }
+    }
+}