1 files changed, 137 insertions, 0 deletions
diff --git a/include/utils/PollLoop.h b/include/utils/PollLoop.h
new file mode 100644
index 0000000..2ec39fe
--- /dev/null
+++ b/include/utils/PollLoop.h
@@ -0,0 +1,137 @@
+/*
+ * Copyright (C) 2010 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.
+ */
+
+#ifndef UTILS_POLL_LOOP_H
+#define UTILS_POLL_LOOP_H
+
+#include <utils/Vector.h>
+#include <utils/threads.h>
+
+#include <poll.h>
+
+namespace android {
+
+/**
+ * A basic file descriptor polling loop based on poll() with callbacks.
+ */
+class PollLoop : public RefBase {
+protected:
+    virtual ~PollLoop();
+
+public:
+    PollLoop();
+
+    /**
+     * A callback that it to be invoked when an event occurs on a file descriptor.
+     * Specifies the events that were triggered and the user data provided when the
+     * callback was set.
+     *
+     * Returns true if the callback should be kept, false if it should be removed automatically
+     * after the callback returns.
+     */
+    typedef bool (*Callback)(int fd, int events, void* data);
+
+    /**
+     * Performs a single call to poll() with optional timeout in milliseconds.
+     * Invokes callbacks for all file descriptors on which an event occurred.
+     *
+     * If the timeout is zero, returns immediately without blocking.
+     * If the timeout is negative, waits indefinitely until awoken.
+     *
+     * Returns true if a callback was invoked or if the loop was awoken by wake().
+     * Returns false if a timeout or error occurred.
+     *
+     * This method must only be called on the main thread.
+     * This method blocks until either a file descriptor is signalled, a timeout occurs,
+     * or wake() is called.
+     * This method does not return until it has finished invoking the appropriate callbacks
+     * for all file descriptors that were signalled.
+     */
+    bool pollOnce(int timeoutMillis);
+
+    /**
+     * Wakes the loop asynchronously.
+     *
+     * This method can be called on any thread.
+     * This method returns immediately.
+     */
+    void wake();
+
+    /**
+     * Sets the callback for a file descriptor, replacing the existing one, if any.
+     * It is an error to call this method with events == 0 or callback == NULL.
+     *
+     * Note that a callback can be invoked with the POLLERR, POLLHUP or POLLNVAL events
+     * even if it is not explicitly requested when registered.
+     *
+     * This method can be called on any thread.
+     * This method may block briefly if it needs to wake the poll loop.
+     */
+    void setCallback(int fd, int events, Callback callback, void* data = NULL);
+
+    /**
+     * Removes the callback for a file descriptor, if one exists.
+     *
+     * When this method returns, it is safe to close the file descriptor since the poll loop
+     * will no longer have a reference to it.  However, it is possible for the callback to
+     * already be running or for it to run one last time if the file descriptor was already
+     * signalled.  Calling code is responsible for ensuring that this case is safely handled.
+     * For example, if the callback takes care of removing itself during its own execution either
+     * by returning false or calling this method, then it can be guaranteed to not be invoked
+     * again at any later time unless registered anew.
+     *
+     * This method can be called on any thread.
+     * This method may block briefly if it needs to wake the poll loop.
+     *
+     * Returns true if a callback was actually removed, false if none was registered.
+     */
+    bool removeCallback(int fd);
+
+private:
+    struct RequestedCallback {
+        Callback callback;
+        void* data;
+    };
+
+    struct PendingCallback {
+        int fd;
+        int events;
+        Callback callback;
+        void* data;
+    };
+
+    Mutex mLock;
+    Condition mAwake;
+    bool mPolling;
+
+    int mWakeReadPipeFd;
+    int mWakeWritePipeFd;
+
+    Vector<struct pollfd> mRequestedFds;
+    Vector<RequestedCallback> mRequestedCallbacks;
+
+    Vector<PendingCallback> mPendingCallbacks; // used privately by pollOnce
+
+    void openWakePipe();
+    void closeWakePipe();
+
+    ssize_t getRequestIndexLocked(int fd);
+    void wakeAndLock();
+};
+
+} // namespace android
+
+#endif // UTILS_POLL_LOOP_H