libs/vibrator/ExternalVibrationUtils.cpp

/*
 * Copyright (C) 2020 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.
 */
#include <cstring>

#include <math.h>

#include <vibrator/ExternalVibrationUtils.h>

namespace android::os {

namespace {
static constexpr float HAPTIC_SCALE_VERY_LOW_RATIO = 2.0f / 3.0f;
static constexpr float HAPTIC_SCALE_LOW_RATIO = 3.0f / 4.0f;
static constexpr float HAPTIC_MAX_AMPLITUDE_FLOAT = 1.0f;

float getHapticScaleGamma(HapticScale scale) {
    switch (scale) {
    case HapticScale::VERY_LOW:
        return 2.0f;
    case HapticScale::LOW:
        return 1.5f;
    case HapticScale::HIGH:
        return 0.5f;
    case HapticScale::VERY_HIGH:
        return 0.25f;
    default:
        return 1.0f;
    }
}

float getHapticMaxAmplitudeRatio(HapticScale scale) {
    switch (scale) {
    case HapticScale::VERY_LOW:
        return HAPTIC_SCALE_VERY_LOW_RATIO;
    case HapticScale::LOW:
        return HAPTIC_SCALE_LOW_RATIO;
    case HapticScale::NONE:
    case HapticScale::HIGH:
    case HapticScale::VERY_HIGH:
        return 1.0f;
    default:
        return 0.0f;
    }
}

} // namespace

bool isValidHapticScale(HapticScale scale) {
    switch (scale) {
    case HapticScale::MUTE:
    case HapticScale::VERY_LOW:
    case HapticScale::LOW:
    case HapticScale::NONE:
    case HapticScale::HIGH:
    case HapticScale::VERY_HIGH:
        return true;
    }
    return false;
}

void scaleHapticData(float* buffer, size_t length, HapticScale scale) {
    if (!isValidHapticScale(scale) || scale == HapticScale::NONE) {
        return;
    }
    if (scale == HapticScale::MUTE) {
        memset(buffer, 0, length * sizeof(float));
        return;
    }
    float gamma = getHapticScaleGamma(scale);
    float maxAmplitudeRatio = getHapticMaxAmplitudeRatio(scale);
    for (size_t i = 0; i < length; i++) {
        float sign = buffer[i] >= 0 ? 1.0 : -1.0;
        buffer[i] = powf(fabsf(buffer[i] / HAPTIC_MAX_AMPLITUDE_FLOAT), gamma)
                * maxAmplitudeRatio * HAPTIC_MAX_AMPLITUDE_FLOAT * sign;
    }
}

} // namespace android::os