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/*
* Copyright (C) 2016 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 com.android.server.display;
import android.util.Slog;
import java.io.PrintWriter;
import java.util.Arrays;
/**
* A helper class for handling access to illuminance hysteresis level values.
*/
final class HysteresisLevels {
private static final String TAG = "HysteresisLevels";
// Default hysteresis constraints for brightening or darkening.
// The recent lux must have changed by at least this fraction relative to the
// current ambient lux before a change will be considered.
private static final float DEFAULT_BRIGHTENING_HYSTERESIS = 0.10f;
private static final float DEFAULT_DARKENING_HYSTERESIS = 0.20f;
private static final boolean DEBUG = false;
private final float[] mBrightLevels;
private final float[] mDarkLevels;
private final float[] mLuxLevels;
/**
* Creates a {@code HysteresisLevels} object with the given equal-length
* integer arrays.
* @param brightLevels an array of brightening hysteresis constraint constants
* @param darkLevels an array of darkening hysteresis constraint constants
* @param luxLevels a monotonically increasing array of illuminance
* thresholds in units of lux
*/
public HysteresisLevels(int[] brightLevels, int[] darkLevels, int[] luxLevels) {
if (brightLevels.length != darkLevels.length || darkLevels.length != luxLevels.length + 1) {
throw new IllegalArgumentException("Mismatch between hysteresis array lengths.");
}
mBrightLevels = setArrayFormat(brightLevels, 1000.0f);
mDarkLevels = setArrayFormat(darkLevels, 1000.0f);
mLuxLevels = setArrayFormat(luxLevels, 1.0f);
}
/**
* Return the brightening hysteresis threshold for the given lux level.
*/
public float getBrighteningThreshold(float lux) {
float brightConstant = getReferenceLevel(lux, mBrightLevels);
float brightThreshold = lux * (1.0f + brightConstant);
if (DEBUG) {
Slog.d(TAG, "bright hysteresis constant=: " + brightConstant + ", threshold="
+ brightThreshold + ", lux=" + lux);
}
return brightThreshold;
}
/**
* Return the darkening hysteresis threshold for the given lux level.
*/
public float getDarkeningThreshold(float lux) {
float darkConstant = getReferenceLevel(lux, mDarkLevels);
float darkThreshold = lux * (1.0f - darkConstant);
if (DEBUG) {
Slog.d(TAG, "dark hysteresis constant=: " + darkConstant + ", threshold="
+ darkThreshold + ", lux=" + lux);
}
return darkThreshold;
}
/**
* Return the hysteresis constant for the closest lux threshold value to the
* current illuminance from the given array.
*/
private float getReferenceLevel(float lux, float[] referenceLevels) {
int index = 0;
while (mLuxLevels.length > index && lux >= mLuxLevels[index]) {
++index;
}
return referenceLevels[index];
}
/**
* Return a float array where each i-th element equals {@code configArray[i]/divideFactor}.
*/
private float[] setArrayFormat(int[] configArray, float divideFactor) {
float[] levelArray = new float[configArray.length];
for (int index = 0; levelArray.length > index; ++index) {
levelArray[index] = (float)configArray[index] / divideFactor;
}
return levelArray;
}
public void dump(PrintWriter pw) {
pw.println("HysteresisLevels");
pw.println(" mBrightLevels=" + Arrays.toString(mBrightLevels));
pw.println(" mDarkLevels=" + Arrays.toString(mDarkLevels));
pw.println(" mLuxLevels=" + Arrays.toString(mLuxLevels));
}
}
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