LinearRamp.cpp revision e572f469de5dca1078a79d3d80e5b04f96ae7505 
1/*
2 * Copyright 2017 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#include "LinearRamp.h"
18
19bool LinearRamp::isRamping() {
20    float target = mTarget.load();
21    if (target != mLevelTo) {
22        // Update target. Continue from previous level.
23        mLevelTo = target;
24        mRemaining = mLengthInFrames;
25        return true;
26    } else {
27        return mRemaining > 0;
28    }
29}
30
31bool LinearRamp::nextSegment(int32_t frames, float *levelFrom, float *levelTo) {
32    bool ramping = isRamping();
33    *levelFrom = mLevelFrom;
34    if (ramping) {
35        float level;
36        if (frames >= mRemaining) {
37            level = mLevelTo;
38            mRemaining = 0;
39        } else {
40            // Interpolate to a point along the full ramp.
41            level = mLevelFrom + (frames * (mLevelTo - mLevelFrom) / mRemaining);
42            mRemaining -= frames;
43        }
44        mLevelFrom = level; // for next ramp
45        *levelTo = level;
46    } else {
47        *levelTo = mLevelTo;
48    }
49    return ramping;
50}