Copyright 2018 Netflix, Inc.
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.
/**
 * Copyright 2018 Netflix, Inc.
 *
 * 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.netflix.concurrency.limits.limit.functions;

import java.util.function.Function;
import java.util.stream.IntStream;

Function used by limiters to calculate thredsholds using log10 of the current limit.  
Here we pre-compute the log10 of numbers up to 1000 as an optimization.
/**
 * Function used by limiters to calculate thredsholds using log10 of the current limit.  
 * Here we pre-compute the log10 of numbers up to 1000 as an optimization.
 */
public final class Log10RootFunction implements Function<Integer, Integer> {
    static final int[] lookup = new int[1000];
    
    static {
        IntStream.range(0, 1000).forEach(i -> lookup[i] = Math.max(1, (int)Math.log10(i)));
    }
    
    private static final Log10RootFunction INSTANCE = new Log10RootFunction();
    
    
Create an instance of a function that returns : baseline + sqrt(limit)
Params:
baseline – 
Returns:
/**
     * Create an instance of a function that returns : baseline + sqrt(limit)
     * 
     * @param baseline
     * @return
     */
    public static Function<Integer, Integer> create(int baseline) {
        return INSTANCE.andThen(t -> t + baseline);
    }
    
    @Override
    public Integer apply(Integer t) {
        return t < 1000 ? lookup[t] : (int)Math.log10(t);
    }
}