hadoop INativeComparable 源码
haddop INativeComparable 代码
文件路径：/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-nativetask/src/main/java/org/apache/hadoop/mapred/nativetask/INativeComparable.java
/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.apache.hadoop.mapred.nativetask;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
/**
* Any key type that is comparable at native side must implement this interface.
*
* A native comparator function should have the ComparatorPtr type:
* <code>
* typedef int (*ComparatorPtr)(const char * src, uint32_t srcLength,
* const char * dest, uint32_t destLength);
* </code>
* Keys are in serialized format at native side. The function has passed in
* the keys' locations and lengths such that we can compare them in the same
* logic as their Java comparator.
*
* For example, a HiveKey serialized as an int field (containing the length of
* raw bytes) + raw bytes.
* When comparing two HiveKeys, we first read the length field and then
* compare the raw bytes by invoking the BytesComparator provided by our library.
* We pass the location and length of raw bytes into BytesComparator.
*
* <code>
* int HivePlatform::HiveKeyComparator(const char * src, uint32_t srcLength,
* const char * dest, uint32_t destLength) {
* uint32_t sl = bswap(*(uint32_t*)src);
* uint32_t dl = bswap(*(uint32_t*)dest);
* return NativeObjectFactory::BytesComparator(src + 4, sl, dest + 4, dl);
* }
* </code>
*/
@InterfaceAudience.Public
@InterfaceStability.Evolving
public interface INativeComparable {
}
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