media/libaaudio/src/flowgraph/resampler/IntegerRatio.cpp

/*
 * Copyright 2019 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 "IntegerRatio.h"

using namespace RESAMPLER_OUTER_NAMESPACE::resampler;

// Enough primes to cover the common sample rates.
static const int kPrimes[] = {
        2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41,
        43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97,
        101, 103, 107, 109, 113, 127, 131, 137, 139, 149,
        151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199};

void IntegerRatio::reduce() {
    for (int prime : kPrimes) {
        if (mNumerator < prime || mDenominator < prime) {
            break;
        }

        // Find biggest prime factor for numerator.
        while (true) {
            int top = mNumerator / prime;
            int bottom = mDenominator / prime;
            if ((top >= 1)
                && (bottom >= 1)
                && (top * prime == mNumerator) // divided evenly?
                && (bottom * prime == mDenominator)) {
                mNumerator = top;
                mDenominator = bottom;
            } else {
                break;
            }
        }

    }
}