MetricUtils.java

/*
 * Copyright 2014 the original author or authors.
 *
 * 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 org.springframework.cloud.stream.module.metrics;

import java.util.List;

/**
 * Utility class, primarily to avoid exposing mutable objects beyond the core package.
 *
 * For internal use only.
 *
 * @author Luke Taylor
 * @author Eric Bottard
 */
public final class MetricUtils {

	/**
	 * Concatenate {@code size} many values from the passed in arrays, starting at offset {@code start}.
	 */
	public static long[] concatArrays(List<long[]> arrays, int start, int size) {
		long[] result = new long[size];

		// How many values we still need to move over
		int howManyLeft = size;

		// Where in the resulting array we're currently bulk-writing
		int targetPosition = 0;

		// Where we're copying *from*, in (one of) the source array.
		// Typically 0, except maybe for the first array in the list
		int from = start;

		for (int i = 0; i < arrays.size() && howManyLeft > 0; i++) {
			long[] current = arrays.get(i);

			// Can't copy more than the current source array size, or the grand total pointer
			int howManyThisRound = Math.min(current.length - from, howManyLeft);
			System.arraycopy(current, from, result, targetPosition, howManyThisRound);
			from = 0;
			howManyLeft -= howManyThisRound;
			targetPosition += howManyThisRound;
		}

		// If this is non-zero here, means we were asked to copy more than what we were provided
		if (howManyLeft > 0) {
			throw new ArrayIndexOutOfBoundsException(
					String.format("Not enough data, short of %d elements", howManyLeft));
		}
		return result;
	}

	public static long sum(long[] array) {
		if (array == null) {
			return 0L;
		}
		long sum = 0;
		for (int i = 0; i < array.length; i++) {
			sum += array[i];
		}
		return sum;
	}

}