com.metamx.metrics.KeyedDiff Maven / Gradle / Ivy
/*
* Copyright 2012 Metamarkets Group 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.metamx.metrics;
import com.metamx.common.logger.Logger;
import java.util.HashMap;
import java.util.Map;
public class KeyedDiff
{
private static final Logger log = new Logger(KeyedDiff.class);
private final Map> prevs = new HashMap>();
public Map to(String key, Map curr)
{
final Map prev = prevs.put(key, curr);
if (prev != null) {
return subtract(curr, prev);
}
else {
log.debug("No previous data for key[%s]", key);
return null;
}
}
public static Map subtract(Map xs, Map ys)
{
assert xs.keySet().equals(ys.keySet());
final Map zs = new HashMap();
for (String k : xs.keySet()) {
zs.put(k, xs.get(k) - ys.get(k));
}
return zs;
}
}