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diff --git a/include/cpustats/ThreadCpuUsage.h b/include/cpustats/ThreadCpuUsage.h
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+/*
+ * Copyright (C) 2011 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 _THREAD_CPU_USAGE_H
+#define _THREAD_CPU_USAGE_H
+
+#include <fcntl.h>
+#include <pthread.h>
+
+namespace android {
+
+// Track CPU usage for the current thread.
+// Units are in per-thread CPU ns, as reported by
+// clock_gettime(CLOCK_THREAD_CPUTIME_ID).  Simple usage: for cyclic
+// threads where you want to measure the execution time of the whole
+// cycle, just call sampleAndEnable() at the start of each cycle.
+// For acyclic threads, or for cyclic threads where you want to measure/track
+// only part of each cycle, call enable(), disable(), and/or setEnabled()
+// to demarcate the region(s) of interest, and then call sample() periodically.
+// This class is not thread-safe for concurrent calls from multiple threads;
+// the methods of this class may only be called by the current thread
+// which constructed the object.
+
+class ThreadCpuUsage
+{
+
+public:
+    ThreadCpuUsage() :
+        mIsEnabled(false),
+        mWasEverEnabled(false),
+        mAccumulator(0),
+        // mPreviousTs
+        // mMonotonicTs
+        mMonotonicKnown(false)
+        {
+            (void) pthread_once(&sOnceControl, &init);
+            for (int i = 0; i < sKernelMax; ++i) {
+                mCurrentkHz[i] = (uint32_t) ~0;   // unknown
+            }
+        }
+
+    ~ThreadCpuUsage() { }
+
+    // Return whether currently tracking CPU usage by current thread
+    bool isEnabled() const  { return mIsEnabled; }
+
+    // Enable tracking of CPU usage by current thread;
+    // any CPU used from this point forward will be tracked.
+    // Returns the previous enabled status.
+    bool enable()       { return setEnabled(true); }
+
+    // Disable tracking of CPU usage by current thread;
+    // any CPU used from this point forward will be ignored.
+    // Returns the previous enabled status.
+    bool disable()      { return setEnabled(false); }
+
+    // Set the enabled status and return the previous enabled status.
+    // This method is intended to be used for safe nested enable/disabling.
+    bool setEnabled(bool isEnabled);
+
+    // Add a sample point, and also enable tracking if needed.
+    // If tracking has never been enabled, then this call enables tracking but
+    // does _not_ add a sample -- it is not possible to add a sample the
+    // first time because there is no previous point to subtract from.
+    // Otherwise, if tracking is enabled,
+    // then adds a sample for tracked CPU ns since the previous
+    // sample, or since the first call to sampleAndEnable(), enable(), or
+    // setEnabled(true).  If there was a previous sample but tracking is
+    // now disabled, then adds a sample for the tracked CPU ns accumulated
+    // up until the most recent disable(), resets this accumulator, and then
+    // enables tracking.  Calling this method rather than enable() followed
+    // by sample() avoids a race condition for the first sample.
+    // Returns true if the sample 'ns' is valid, or false if invalid.
+    // Note that 'ns' is an output parameter passed by reference.
+    // The caller does not need to initialize this variable.
+    // The units are CPU nanoseconds consumed by current thread.
+    bool sampleAndEnable(double& ns);
+
+    // Add a sample point, but do not
+    // change the tracking enabled status.  If tracking has either never been
+    // enabled, or has never been enabled since the last sample, then log a warning
+    // and don't add sample.  Otherwise, adds a sample for tracked CPU ns since
+    // the previous sample or since the first call to sampleAndEnable(),
+    // enable(), or setEnabled(true) if no previous sample.
+    // Returns true if the sample is valid, or false if invalid.
+    // Note that 'ns' is an output parameter passed by reference.
+    // The caller does not need to initialize this variable.
+    // The units are CPU nanoseconds consumed by current thread.
+    bool sample(double& ns);
+
+    // Return the elapsed delta wall clock ns since initial enable or reset,
+    // as reported by clock_gettime(CLOCK_MONOTONIC).
+    long long elapsed() const;
+
+    // Reset elapsed wall clock.  Has no effect on tracking or accumulator.
+    void resetElapsed();
+
+    // Return current clock frequency for specified CPU, in kHz.
+    // You can get your CPU number using sched_getcpu(2).  Note that, unless CPU affinity
+    // has been configured appropriately, the CPU number can change.
+    // Also note that, unless the CPU governor has been configured appropriately,
+    // the CPU frequency can change.  And even if the CPU frequency is locked down
+    // to a particular value, that the frequency might still be adjusted
+    // to prevent thermal overload.  Therefore you should poll for your thread's
+    // current CPU number and clock frequency periodically.
+    uint32_t getCpukHz(int cpuNum);
+
+private:
+    bool mIsEnabled;                // whether tracking is currently enabled
+    bool mWasEverEnabled;           // whether tracking was ever enabled
+    long long mAccumulator;         // accumulated thread CPU time since last sample, in ns
+    struct timespec mPreviousTs;    // most recent thread CPU time, valid only if mIsEnabled is true
+    struct timespec mMonotonicTs;   // most recent monotonic time
+    bool mMonotonicKnown;           // whether mMonotonicTs has been set
+
+    static const int MAX_CPU = 8;
+    static int sScalingFds[MAX_CPU];// file descriptor per CPU for reading scaling_cur_freq
+    uint32_t mCurrentkHz[MAX_CPU];  // current CPU frequency in kHz, not static to avoid a race
+    static pthread_once_t sOnceControl;
+    static int sKernelMax;          // like MAX_CPU, but determined at runtime == cpu/kernel_max + 1
+    static void init();             // called once at first ThreadCpuUsage construction
+    static pthread_mutex_t sMutex;  // protects sScalingFds[] after initialization
+};
+
+}   // namespace android
+
+#endif //  _THREAD_CPU_USAGE_H