diff --git a/libs/utils/Android.mk b/libs/utils/Android.mk
index afecdcb..945b039 100644
--- a/libs/utils/Android.mk
+++ b/libs/utils/Android.mk
@@ -26,6 +26,8 @@
 	Debug.cpp \
 	FileMap.cpp \
 	Flattenable.cpp \
+	PollLoop.cpp \
+	Pool.cpp \
 	RefBase.cpp \
 	ResourceTypes.cpp \
 	SharedBuffer.cpp \
diff --git a/libs/utils/PollLoop.cpp b/libs/utils/PollLoop.cpp
new file mode 100644
index 0000000..90a3e8b
--- /dev/null
+++ b/libs/utils/PollLoop.cpp
@@ -0,0 +1,267 @@
+//
+// Copyright 2010 The Android Open Source Project
+//
+// A select loop implementation.
+//
+#define LOG_TAG "PollLoop"
+
+//#define LOG_NDEBUG 0
+
+// Debugs poll and wake interactions.
+#define DEBUG_POLL_AND_WAKE 0
+
+// Debugs callback registration and invocation.
+#define DEBUG_CALLBACKS 1
+
+#include <cutils/log.h>
+#include <utils/PollLoop.h>
+
+#include <unistd.h>
+#include <fcntl.h>
+
+namespace android {
+
+PollLoop::PollLoop() :
+        mPolling(false) {
+    openWakePipe();
+}
+
+PollLoop::~PollLoop() {
+    closeWakePipe();
+}
+
+void PollLoop::openWakePipe() {
+    int wakeFds[2];
+    int result = pipe(wakeFds);
+    LOG_ALWAYS_FATAL_IF(result != 0, "Could not create wake pipe.  errno=%d", errno);
+
+    mWakeReadPipeFd = wakeFds[0];
+    mWakeWritePipeFd = wakeFds[1];
+
+    result = fcntl(mWakeReadPipeFd, F_SETFL, O_NONBLOCK);
+    LOG_ALWAYS_FATAL_IF(result != 0, "Could not make wake read pipe non-blocking.  errno=%d",
+            errno);
+
+    result = fcntl(mWakeWritePipeFd, F_SETFL, O_NONBLOCK);
+    LOG_ALWAYS_FATAL_IF(result != 0, "Could not make wake write pipe non-blocking.  errno=%d",
+            errno);
+
+    // Add the wake pipe to the head of the request list with a null callback.
+    struct pollfd requestedFd;
+    requestedFd.fd = mWakeReadPipeFd;
+    requestedFd.events = POLLIN;
+    mRequestedFds.insertAt(requestedFd, 0);
+
+    RequestedCallback requestedCallback;
+    requestedCallback.callback = NULL;
+    requestedCallback.data = NULL;
+    mRequestedCallbacks.insertAt(requestedCallback, 0);
+}
+
+void PollLoop::closeWakePipe() {
+    close(mWakeReadPipeFd);
+    close(mWakeWritePipeFd);
+
+    // Note: We don't need to remove the poll structure or callback entry because this
+    //       method is currently only called by the destructor.
+}
+
+bool PollLoop::pollOnce(int timeoutMillis) {
+    mLock.lock();
+    mPolling = true;
+    mLock.unlock();
+
+    bool result;
+    size_t requestedCount = mRequestedFds.size();
+
+#if DEBUG_POLL_AND_WAKE
+    LOGD("%p ~ pollOnce - waiting on %d fds", this, requestedCount);
+    for (size_t i = 0; i < requestedCount; i++) {
+        LOGD("  fd %d - events %d", mRequestedFds[i].fd, mRequestedFds[i].events);
+    }
+#endif
+
+    int respondedCount = poll(mRequestedFds.editArray(), requestedCount, timeoutMillis);
+
+    if (respondedCount == 0) {
+        // Timeout
+#if DEBUG_POLL_AND_WAKE
+        LOGD("%p ~ pollOnce - timeout", this);
+#endif
+        result = false;
+        goto Done;
+    }
+
+    if (respondedCount < 0) {
+        // Error
+#if DEBUG_POLL_AND_WAKE
+        LOGD("%p ~ pollOnce - error, errno=%d", this, errno);
+#endif
+        if (errno != EINTR) {
+            LOGW("Poll failed with an unexpected error, errno=%d", errno);
+        }
+        result = false;
+        goto Done;
+    }
+
+#if DEBUG_POLL_AND_WAKE
+    LOGD("%p ~ pollOnce - handling responses from %d fds", this, respondedCount);
+    for (size_t i = 0; i < requestedCount; i++) {
+        LOGD("  fd %d - events %d, revents %d", mRequestedFds[i].fd, mRequestedFds[i].events,
+                mRequestedFds[i].revents);
+    }
+#endif
+
+    mPendingCallbacks.clear();
+    for (size_t i = 0; i < requestedCount; i++) {
+        const struct pollfd& requestedFd = mRequestedFds.itemAt(i);
+
+        short revents = requestedFd.revents;
+        if (revents) {
+            const RequestedCallback& requestedCallback = mRequestedCallbacks.itemAt(i);
+            Callback callback = requestedCallback.callback;
+
+            if (callback) {
+                PendingCallback pendingCallback;
+                pendingCallback.fd = requestedFd.fd;
+                pendingCallback.events = requestedFd.revents;
+                pendingCallback.callback = callback;
+                pendingCallback.data = requestedCallback.data;
+                mPendingCallbacks.push(pendingCallback);
+            } else {
+                if (requestedFd.fd == mWakeReadPipeFd) {
+#if DEBUG_POLL_AND_WAKE
+                    LOGD("%p ~ pollOnce - awoken", this);
+#endif
+                    char buffer[16];
+                    ssize_t nRead;
+                    do {
+                        nRead = read(mWakeReadPipeFd, buffer, sizeof(buffer));
+                    } while (nRead == sizeof(buffer));
+                } else {
+#if DEBUG_POLL_AND_WAKE || DEBUG_CALLBACKS
+                    LOGD("%p ~ pollOnce - fd %d has no callback!", this, requestedFd.fd);
+#endif
+                }
+            }
+
+            respondedCount -= 1;
+            if (respondedCount == 0) {
+                break;
+            }
+        }
+    }
+    result = true;
+
+Done:
+    mLock.lock();
+    mPolling = false;
+    mAwake.broadcast();
+    mLock.unlock();
+
+    if (result) {
+        size_t pendingCount = mPendingCallbacks.size();
+        for (size_t i = 0; i < pendingCount; i++) {
+            const PendingCallback& pendingCallback = mPendingCallbacks.itemAt(i);
+#if DEBUG_POLL_AND_WAKE || DEBUG_CALLBACKS
+            LOGD("%p ~ pollOnce - invoking callback for fd %d", this, pendingCallback.fd);
+#endif
+
+            bool keep = pendingCallback.callback(pendingCallback.fd, pendingCallback.events,
+                    pendingCallback.data);
+            if (! keep) {
+                removeCallback(pendingCallback.fd);
+            }
+        }
+    }
+
+#if DEBUG_POLL_AND_WAKE
+    LOGD("%p ~ pollOnce - done", this);
+#endif
+    return result;
+}
+
+void PollLoop::wake() {
+#if DEBUG_POLL_AND_WAKE
+    LOGD("%p ~ wake", this);
+#endif
+
+    ssize_t nWrite = write(mWakeWritePipeFd, "W", 1);
+    if (nWrite != 1) {
+        if (errno != EAGAIN) {
+            LOGW("Could not write wake signal, errno=%d", errno);
+        }
+    }
+}
+
+void PollLoop::setCallback(int fd, int events, Callback callback, void* data) {
+#if DEBUG_CALLBACKS
+    LOGD("%p ~ setCallback - fd=%d, events=%d", this, fd, events);
+#endif
+
+    if (! events || ! callback) {
+        LOGE("Invalid attempt to set a callback with no selected poll events or no callback.");
+        removeCallback(fd);
+        return;
+    }
+
+    wakeAndLock();
+
+    struct pollfd requestedFd;
+    requestedFd.fd = fd;
+    requestedFd.events = events;
+
+    RequestedCallback requestedCallback;
+    requestedCallback.callback = callback;
+    requestedCallback.data = data;
+
+    ssize_t index = getRequestIndexLocked(fd);
+    if (index < 0) {
+        mRequestedFds.push(requestedFd);
+        mRequestedCallbacks.push(requestedCallback);
+    } else {
+        mRequestedFds.replaceAt(requestedFd, size_t(index));
+        mRequestedCallbacks.replaceAt(requestedCallback, size_t(index));
+    }
+
+    mLock.unlock();
+}
+
+bool PollLoop::removeCallback(int fd) {
+#if DEBUG_CALLBACKS
+    LOGD("%p ~ removeCallback - fd=%d", this, fd);
+#endif
+
+    wakeAndLock();
+
+    ssize_t index = getRequestIndexLocked(fd);
+    if (index >= 0) {
+        mRequestedFds.removeAt(size_t(index));
+        mRequestedCallbacks.removeAt(size_t(index));
+    }
+
+    mLock.unlock();
+    return index >= 0;
+}
+
+ssize_t PollLoop::getRequestIndexLocked(int fd) {
+    size_t requestCount = mRequestedFds.size();
+
+    for (size_t i = 0; i < requestCount; i++) {
+        if (mRequestedFds.itemAt(i).fd == fd) {
+            return i;
+        }
+    }
+
+    return -1;
+}
+
+void PollLoop::wakeAndLock() {
+    mLock.lock();
+    while (mPolling) {
+        wake();
+        mAwake.wait(mLock);
+    }
+}
+
+} // namespace android
diff --git a/libs/utils/Pool.cpp b/libs/utils/Pool.cpp
new file mode 100644
index 0000000..8f18cb9
--- /dev/null
+++ b/libs/utils/Pool.cpp
@@ -0,0 +1,37 @@
+//
+// Copyright 2010 The Android Open Source Project
+//
+// A simple memory pool.
+//
+#define LOG_TAG "Pool"
+
+//#define LOG_NDEBUG 0
+
+#include <cutils/log.h>
+#include <utils/Pool.h>
+
+#include <stdlib.h>
+
+namespace android {
+
+// TODO Provide a real implementation of a pool.  This is just a stub for initial development.
+
+PoolImpl::PoolImpl(size_t objSize) :
+    mObjSize(objSize) {
+}
+
+PoolImpl::~PoolImpl() {
+}
+
+void* PoolImpl::allocImpl() {
+    void* ptr = malloc(mObjSize);
+    LOG_ALWAYS_FATAL_IF(ptr == NULL, "Cannot allocate new pool object.");
+    return ptr;
+}
+
+void PoolImpl::freeImpl(void* obj) {
+    LOG_ALWAYS_FATAL_IF(obj == NULL, "Caller attempted to free NULL pool object.");
+    return free(obj);
+}
+
+} // namespace android
diff --git a/libs/utils/StopWatch.cpp b/libs/utils/StopWatch.cpp
index 68a1c52..b5dda2f 100644
--- a/libs/utils/StopWatch.cpp
+++ b/libs/utils/StopWatch.cpp
@@ -30,10 +30,9 @@
 
 
 StopWatch::StopWatch(const char *name, int clock, uint32_t flags)
-    :   mName(name), mClock(clock), mFlags(flags),
-        mStartTime(0), mNumLaps(0)
+    :   mName(name), mClock(clock), mFlags(flags)
 {
-    mStartTime = systemTime(mClock);
+    reset();
 }
 
 StopWatch::~StopWatch()
@@ -72,6 +71,12 @@
     return systemTime(mClock) - mStartTime;
 }
 
+void StopWatch::reset()
+{
+    mNumLaps = 0;
+    mStartTime = systemTime(mClock);
+}
+
 
 /*****************************************************************************/
 
diff --git a/libs/utils/VectorImpl.cpp b/libs/utils/VectorImpl.cpp
index 0322af7..b09c6ca 100644
--- a/libs/utils/VectorImpl.cpp
+++ b/libs/utils/VectorImpl.cpp
@@ -108,13 +108,7 @@
 
 ssize_t VectorImpl::insertVectorAt(const VectorImpl& vector, size_t index)
 {
-    if (index > size())
-        return BAD_INDEX;
-    void* where = _grow(index, vector.size());
-    if (where) {
-        _do_copy(where, vector.arrayImpl(), vector.size());
-    }
-    return where ? index : (ssize_t)NO_MEMORY;
+    return insertAt(vector.arrayImpl(), index, vector.size());
 }
 
 ssize_t VectorImpl::appendVector(const VectorImpl& vector)
@@ -226,9 +220,9 @@
     return add(0);
 }
 
-ssize_t VectorImpl::add(const void* item)
+ssize_t VectorImpl::add(const void* item, size_t numItems)
 {
-    return insertAt(item, size());
+    return insertAt(item, size(), numItems);
 }
 
 ssize_t VectorImpl::replaceAt(size_t index)
diff --git a/libs/utils/tests/Android.mk b/libs/utils/tests/Android.mk
new file mode 100644
index 0000000..45e8061
--- /dev/null
+++ b/libs/utils/tests/Android.mk
@@ -0,0 +1,33 @@
+# Build the unit tests.
+LOCAL_PATH := $(call my-dir)
+include $(CLEAR_VARS)
+
+test_src_files := \
+	PollLoop_test.cpp
+
+LOCAL_SHARED_LIBRARIES := \
+	libz \
+	liblog \
+	libcutils \
+	libutils \
+	libstlport
+
+LOCAL_STATIC_LIBRARIES := \
+	libgtest \
+	libgtest_main
+
+LOCAL_C_INCLUDES := \
+    external/zlib \
+    external/icu4c/common \
+    bionic \
+    bionic/libstdc++/include \
+    external/gtest/include \
+    external/stlport/stlport
+
+LOCAL_MODULE_TAGS := eng tests
+
+$(foreach file,$(test_src_files), \
+    $(eval LOCAL_SRC_FILES := $(file)) \
+    $(eval LOCAL_MODULE := $(notdir $(file:%.cpp=%))) \
+    $(eval include $(BUILD_EXECUTABLE)) \
+)
diff --git a/libs/utils/tests/PollLoop_test.cpp b/libs/utils/tests/PollLoop_test.cpp
new file mode 100644
index 0000000..6c719c8
--- /dev/null
+++ b/libs/utils/tests/PollLoop_test.cpp
@@ -0,0 +1,398 @@
+//
+// Copyright 2010 The Android Open Source Project
+//
+
+#include <utils/PollLoop.h>
+#include <utils/Timers.h>
+#include <utils/StopWatch.h>
+#include <gtest/gtest.h>
+#include <unistd.h>
+#include <time.h>
+
+#include "TestHelpers.h"
+
+// # of milliseconds to fudge stopwatch measurements
+#define TIMING_TOLERANCE_MS 25
+
+namespace android {
+
+class Pipe {
+public:
+    int sendFd;
+    int receiveFd;
+
+    Pipe() {
+        int fds[2];
+        ::pipe(fds);
+
+        receiveFd = fds[0];
+        sendFd = fds[1];
+    }
+
+    ~Pipe() {
+        ::close(sendFd);
+        ::close(receiveFd);
+    }
+
+    bool writeSignal() {
+        return ::write(sendFd, "*", 1) == 1;
+    }
+
+    bool readSignal() {
+        char buf[1];
+        return ::read(receiveFd, buf, 1) == 1;
+    }
+};
+
+class DelayedWake : public DelayedTask {
+    sp<PollLoop> mPollLoop;
+
+public:
+    DelayedWake(int delayMillis, const sp<PollLoop> pollLoop) :
+        DelayedTask(delayMillis), mPollLoop(pollLoop) {
+    }
+
+protected:
+    virtual void doTask() {
+        mPollLoop->wake();
+    }
+};
+
+class DelayedWriteSignal : public DelayedTask {
+    Pipe* mPipe;
+
+public:
+    DelayedWriteSignal(int delayMillis, Pipe* pipe) :
+        DelayedTask(delayMillis), mPipe(pipe) {
+    }
+
+protected:
+    virtual void doTask() {
+        mPipe->writeSignal();
+    }
+};
+
+class CallbackHandler {
+public:
+    void setCallback(const sp<PollLoop>& pollLoop, int fd, int events) {
+        pollLoop->setCallback(fd, events, staticHandler, this);
+    }
+
+protected:
+    virtual ~CallbackHandler() { }
+
+    virtual bool handler(int fd, int events) = 0;
+
+private:
+    static bool staticHandler(int fd, int events, void* data) {
+        return static_cast<CallbackHandler*>(data)->handler(fd, events);
+    }
+};
+
+class StubCallbackHandler : public CallbackHandler {
+public:
+    bool nextResult;
+    int callbackCount;
+
+    int fd;
+    int events;
+
+    StubCallbackHandler(bool nextResult) : nextResult(nextResult),
+            callbackCount(0), fd(-1), events(-1) {
+    }
+
+protected:
+    virtual bool handler(int fd, int events) {
+        callbackCount += 1;
+        this->fd = fd;
+        this->events = events;
+        return nextResult;
+    }
+};
+
+class PollLoopTest : public testing::Test {
+protected:
+    sp<PollLoop> mPollLoop;
+
+    virtual void SetUp() {
+        mPollLoop = new PollLoop();
+    }
+
+    virtual void TearDown() {
+        mPollLoop.clear();
+    }
+};
+
+
+TEST_F(PollLoopTest, PollOnce_WhenNonZeroTimeoutAndNotAwoken_WaitsForTimeoutAndReturnsFalse) {
+    StopWatch stopWatch("pollOnce");
+    bool result = mPollLoop->pollOnce(100);
+    int32_t elapsedMillis = ns2ms(stopWatch.elapsedTime());
+
+    EXPECT_NEAR(100, elapsedMillis, TIMING_TOLERANCE_MS)
+            << "elapsed time should approx. equal timeout";
+    EXPECT_FALSE(result)
+            << "pollOnce result should be false because timeout occurred";
+}
+
+TEST_F(PollLoopTest, PollOnce_WhenNonZeroTimeoutAndAwokenBeforeWaiting_ImmediatelyReturnsTrue) {
+    mPollLoop->wake();
+
+    StopWatch stopWatch("pollOnce");
+    bool result = mPollLoop->pollOnce(1000);
+    int32_t elapsedMillis = ns2ms(stopWatch.elapsedTime());
+
+    EXPECT_NEAR(0, elapsedMillis, TIMING_TOLERANCE_MS)
+            << "elapsed time should approx. zero because wake() was called before waiting";
+    EXPECT_TRUE(result)
+            << "pollOnce result should be true because loop was awoken";
+}
+
+TEST_F(PollLoopTest, PollOnce_WhenNonZeroTimeoutAndAwokenWhileWaiting_PromptlyReturnsTrue) {
+    sp<DelayedWake> delayedWake = new DelayedWake(100, mPollLoop);
+    delayedWake->run();
+
+    StopWatch stopWatch("pollOnce");
+    bool result = mPollLoop->pollOnce(1000);
+    int32_t elapsedMillis = ns2ms(stopWatch.elapsedTime());
+
+    EXPECT_NEAR(100, elapsedMillis, TIMING_TOLERANCE_MS)
+            << "elapsed time should approx. equal wake delay";
+    EXPECT_TRUE(result)
+            << "pollOnce result should be true because loop was awoken";
+}
+
+TEST_F(PollLoopTest, PollOnce_WhenZeroTimeoutAndNoRegisteredFDs_ImmediatelyReturnsFalse) {
+    StopWatch stopWatch("pollOnce");
+    bool result = mPollLoop->pollOnce(0);
+    int32_t elapsedMillis = ns2ms(stopWatch.elapsedTime());
+
+    EXPECT_NEAR(0, elapsedMillis, TIMING_TOLERANCE_MS)
+            << "elapsed time should be approx. zero";
+    EXPECT_FALSE(result)
+            << "pollOnce result should be false because timeout occurred";
+}
+
+TEST_F(PollLoopTest, PollOnce_WhenZeroTimeoutAndNoSignalledFDs_ImmediatelyReturnsFalse) {
+    Pipe pipe;
+    StubCallbackHandler handler(true);
+
+    handler.setCallback(mPollLoop, pipe.receiveFd, POLL_IN);
+
+    StopWatch stopWatch("pollOnce");
+    bool result = mPollLoop->pollOnce(0);
+    int32_t elapsedMillis = ns2ms(stopWatch.elapsedTime());
+
+    EXPECT_NEAR(0, elapsedMillis, TIMING_TOLERANCE_MS)
+            << "elapsed time should be approx. zero";
+    EXPECT_FALSE(result)
+            << "pollOnce result should be false because timeout occurred";
+    EXPECT_EQ(0, handler.callbackCount)
+            << "callback should not have been invoked because FD was not signalled";
+}
+
+TEST_F(PollLoopTest, PollOnce_WhenZeroTimeoutAndSignalledFD_ImmediatelyInvokesCallbackAndReturnsTrue) {
+    Pipe pipe;
+    StubCallbackHandler handler(true);
+
+    ASSERT_TRUE(pipe.writeSignal());
+    handler.setCallback(mPollLoop, pipe.receiveFd, POLL_IN);
+
+    StopWatch stopWatch("pollOnce");
+    bool result = mPollLoop->pollOnce(0);
+    int32_t elapsedMillis = ns2ms(stopWatch.elapsedTime());
+
+    EXPECT_NEAR(0, elapsedMillis, TIMING_TOLERANCE_MS)
+            << "elapsed time should be approx. zero";
+    EXPECT_TRUE(result)
+            << "pollOnce result should be true because FD was signalled";
+    EXPECT_EQ(1, handler.callbackCount)
+            << "callback should be invoked exactly once";
+    EXPECT_EQ(pipe.receiveFd, handler.fd)
+            << "callback should have received pipe fd as parameter";
+    EXPECT_EQ(POLL_IN, handler.events)
+            << "callback should have received POLL_IN as events";
+}
+
+TEST_F(PollLoopTest, PollOnce_WhenNonZeroTimeoutAndNoSignalledFDs_WaitsForTimeoutAndReturnsFalse) {
+    Pipe pipe;
+    StubCallbackHandler handler(true);
+
+    handler.setCallback(mPollLoop, pipe.receiveFd, POLL_IN);
+
+    StopWatch stopWatch("pollOnce");
+    bool result = mPollLoop->pollOnce(100);
+    int32_t elapsedMillis = ns2ms(stopWatch.elapsedTime());
+
+    EXPECT_NEAR(100, elapsedMillis, TIMING_TOLERANCE_MS)
+            << "elapsed time should approx. equal timeout";
+    EXPECT_FALSE(result)
+            << "pollOnce result should be false because timeout occurred";
+    EXPECT_EQ(0, handler.callbackCount)
+            << "callback should not have been invoked because FD was not signalled";
+}
+
+TEST_F(PollLoopTest, PollOnce_WhenNonZeroTimeoutAndSignalledFDBeforeWaiting_ImmediatelyInvokesCallbackAndReturnsTrue) {
+    Pipe pipe;
+    StubCallbackHandler handler(true);
+
+    pipe.writeSignal();
+    handler.setCallback(mPollLoop, pipe.receiveFd, POLL_IN);
+
+    StopWatch stopWatch("pollOnce");
+    bool result = mPollLoop->pollOnce(100);
+    int32_t elapsedMillis = ns2ms(stopWatch.elapsedTime());
+
+    ASSERT_TRUE(pipe.readSignal())
+            << "signal should actually have been written";
+    EXPECT_NEAR(0, elapsedMillis, TIMING_TOLERANCE_MS)
+            << "elapsed time should be approx. zero";
+    EXPECT_TRUE(result)
+            << "pollOnce result should be true because FD was signalled";
+    EXPECT_EQ(1, handler.callbackCount)
+            << "callback should be invoked exactly once";
+    EXPECT_EQ(pipe.receiveFd, handler.fd)
+            << "callback should have received pipe fd as parameter";
+    EXPECT_EQ(POLL_IN, handler.events)
+            << "callback should have received POLL_IN as events";
+}
+
+TEST_F(PollLoopTest, PollOnce_WhenNonZeroTimeoutAndSignalledFDWhileWaiting_PromptlyInvokesCallbackAndReturnsTrue) {
+    Pipe pipe;
+    StubCallbackHandler handler(true);
+    sp<DelayedWriteSignal> delayedWriteSignal = new DelayedWriteSignal(100, & pipe);
+
+    handler.setCallback(mPollLoop, pipe.receiveFd, POLL_IN);
+    delayedWriteSignal->run();
+
+    StopWatch stopWatch("pollOnce");
+    bool result = mPollLoop->pollOnce(1000);
+    int32_t elapsedMillis = ns2ms(stopWatch.elapsedTime());
+
+    ASSERT_TRUE(pipe.readSignal())
+            << "signal should actually have been written";
+    EXPECT_NEAR(100, elapsedMillis, TIMING_TOLERANCE_MS)
+            << "elapsed time should approx. equal signal delay";
+    EXPECT_TRUE(result)
+            << "pollOnce result should be true because FD was signalled";
+    EXPECT_EQ(1, handler.callbackCount)
+            << "callback should be invoked exactly once";
+    EXPECT_EQ(pipe.receiveFd, handler.fd)
+            << "callback should have received pipe fd as parameter";
+    EXPECT_EQ(POLL_IN, handler.events)
+            << "callback should have received POLL_IN as events";
+}
+
+TEST_F(PollLoopTest, PollOnce_WhenCallbackAddedThenRemoved_CallbackShouldNotBeInvoked) {
+    Pipe pipe;
+    StubCallbackHandler handler(true);
+
+    handler.setCallback(mPollLoop, pipe.receiveFd, POLL_IN);
+    pipe.writeSignal(); // would cause FD to be considered signalled
+    mPollLoop->removeCallback(pipe.receiveFd);
+
+    StopWatch stopWatch("pollOnce");
+    bool result = mPollLoop->pollOnce(100);
+    int32_t elapsedMillis = ns2ms(stopWatch.elapsedTime());
+
+    ASSERT_TRUE(pipe.readSignal())
+            << "signal should actually have been written";
+    EXPECT_NEAR(100, elapsedMillis, TIMING_TOLERANCE_MS)
+            << "elapsed time should approx. equal timeout because FD was no longer registered";
+    EXPECT_FALSE(result)
+            << "pollOnce result should be false because timeout occurred";
+    EXPECT_EQ(0, handler.callbackCount)
+            << "callback should not be invoked";
+}
+
+TEST_F(PollLoopTest, PollOnce_WhenCallbackReturnsFalse_CallbackShouldNotBeInvokedAgainLater) {
+    Pipe pipe;
+    StubCallbackHandler handler(false);
+
+    handler.setCallback(mPollLoop, pipe.receiveFd, POLL_IN);
+
+    // First loop: Callback is registered and FD is signalled.
+    pipe.writeSignal();
+
+    StopWatch stopWatch("pollOnce");
+    bool result = mPollLoop->pollOnce(0);
+    int32_t elapsedMillis = ns2ms(stopWatch.elapsedTime());
+
+    ASSERT_TRUE(pipe.readSignal())
+            << "signal should actually have been written";
+    EXPECT_NEAR(0, elapsedMillis, TIMING_TOLERANCE_MS)
+            << "elapsed time should approx. equal zero because FD was already signalled";
+    EXPECT_TRUE(result)
+            << "pollOnce result should be true because FD was signalled";
+    EXPECT_EQ(1, handler.callbackCount)
+            << "callback should be invoked";
+
+    // Second loop: Callback is no longer registered and FD is signalled.
+    pipe.writeSignal();
+
+    stopWatch.reset();
+    result = mPollLoop->pollOnce(0);
+    elapsedMillis = ns2ms(stopWatch.elapsedTime());
+
+    ASSERT_TRUE(pipe.readSignal())
+            << "signal should actually have been written";
+    EXPECT_NEAR(0, elapsedMillis, TIMING_TOLERANCE_MS)
+            << "elapsed time should approx. equal zero because timeout was zero";
+    EXPECT_FALSE(result)
+            << "pollOnce result should be false because timeout occurred";
+    EXPECT_EQ(1, handler.callbackCount)
+            << "callback should not be invoked this time";
+}
+
+TEST_F(PollLoopTest, RemoveCallback_WhenCallbackNotAdded_ReturnsFalse) {
+    bool result = mPollLoop->removeCallback(1);
+
+    EXPECT_FALSE(result)
+            << "removeCallback should return false because FD not registered";
+}
+
+TEST_F(PollLoopTest, RemoveCallback_WhenCallbackAddedThenRemovedTwice_ReturnsTrueFirstTimeAndReturnsFalseSecondTime) {
+    Pipe pipe;
+    StubCallbackHandler handler(false);
+    handler.setCallback(mPollLoop, pipe.receiveFd, POLL_IN);
+
+    // First time.
+    bool result = mPollLoop->removeCallback(pipe.receiveFd);
+
+    EXPECT_TRUE(result)
+            << "removeCallback should return true first time because FD was registered";
+
+    // Second time.
+    result = mPollLoop->removeCallback(pipe.receiveFd);
+
+    EXPECT_FALSE(result)
+            << "removeCallback should return false second time because FD was no longer registered";
+}
+
+TEST_F(PollLoopTest, PollOnce_WhenCallbackAddedTwice_OnlySecondCallbackShouldBeInvoked) {
+    Pipe pipe;
+    StubCallbackHandler handler1(true);
+    StubCallbackHandler handler2(true);
+
+    handler1.setCallback(mPollLoop, pipe.receiveFd, POLL_IN);
+    handler2.setCallback(mPollLoop, pipe.receiveFd, POLL_IN); // replace it
+    pipe.writeSignal(); // would cause FD to be considered signalled
+
+    StopWatch stopWatch("pollOnce");
+    bool result = mPollLoop->pollOnce(100);
+    int32_t elapsedMillis = ns2ms(stopWatch.elapsedTime());
+
+    ASSERT_TRUE(pipe.readSignal())
+            << "signal should actually have been written";
+    EXPECT_NEAR(0, elapsedMillis, TIMING_TOLERANCE_MS)
+            << "elapsed time should approx. zero because FD was already signalled";
+    EXPECT_TRUE(result)
+            << "pollOnce result should be true because FD was signalled";
+    EXPECT_EQ(0, handler1.callbackCount)
+            << "original handler callback should not be invoked because it was replaced";
+    EXPECT_EQ(1, handler2.callbackCount)
+            << "replacement handler callback should be invoked";
+}
+
+
+} // namespace android
diff --git a/libs/utils/tests/TestHelpers.h b/libs/utils/tests/TestHelpers.h
new file mode 100644
index 0000000..e55af3c
--- /dev/null
+++ b/libs/utils/tests/TestHelpers.h
@@ -0,0 +1,44 @@
+/*
+ * 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 TESTHELPERS_H
+#define TESTHELPERS_H
+
+#include <utils/threads.h>
+
+namespace android {
+
+class DelayedTask : public Thread {
+    int mDelayMillis;
+
+public:
+    DelayedTask(int delayMillis) : mDelayMillis(delayMillis) { }
+
+protected:
+    virtual ~DelayedTask() { }
+
+    virtual void doTask() = 0;
+
+    virtual bool threadLoop() {
+        usleep(mDelayMillis * 1000);
+        doTask();
+        return false;
+    }
+};
+
+} // namespace android
+
+#endif // TESTHELPERS_H