com.xiaomi.linden.hadoop.indexing.reduce.RAMDirectoryUtil.java Source code

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Here is the source code for com.xiaomi.linden.hadoop.indexing.reduce.RAMDirectoryUtil.java

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// Copyright 2016 Xiaomi, 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.xiaomi.linden.hadoop.indexing.reduce;

import org.apache.hadoop.io.Text;
import org.apache.lucene.store.IOContext;
import org.apache.lucene.store.IndexInput;
import org.apache.lucene.store.IndexOutput;
import org.apache.lucene.store.RAMDirectory;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;

/**
 * A utility class which writes an index in a ram dir into a DataOutput and
 * read from a DataInput an index into a ram dir.
 */
public class RAMDirectoryUtil {
    private static final int BUFFER_SIZE = 1024; // RAMOutputStream.BUFFER_SIZE;

    /**
     * Write a number of files from a ram directory to a data output.
     * @param out  the data output
     * @param dir  the ram directory
     * @throws IOException
     */
    public static void writeRAMFiles(DataOutput out, RAMDirectory dir) throws IOException {
        String[] names = dir.listAll();
        out.writeInt(names.length);
        for (int i = 0; i < names.length; i++) {
            Text.writeString(out, names[i]);
            long length = dir.fileLength(names[i]);
            out.writeLong(length);

            if (length > 0) {
                // can we avoid the extra copy?
                IndexInput input = null;
                try {
                    IOContext context = new IOContext();
                    input = dir.openInput(names[i], context);

                    int position = 0;
                    byte[] buffer = new byte[BUFFER_SIZE];

                    while (position < length) {
                        int len = position + BUFFER_SIZE <= length ? BUFFER_SIZE : (int) (length - position);
                        input.readBytes(buffer, 0, len);
                        out.write(buffer, 0, len);
                        position += len;
                    }
                } finally {
                    if (input != null) {
                        input.close();
                    }
                }
            }
        }
    }

    /**
     * Read a number of files from a data input to a ram directory.
     * @param in  the data input
     * @param dir  the ram directory
     * @throws IOException
     */
    public static void readRAMFiles(DataInput in, RAMDirectory dir) throws IOException {
        int numFiles = in.readInt();

        for (int i = 0; i < numFiles; i++) {
            String name = Text.readString(in);
            long length = in.readLong();

            if (length > 0) {
                // can we avoid the extra copy?
                IndexOutput output = null;
                try {
                    IOContext context = new IOContext();
                    output = dir.createOutput(name, context);

                    int position = 0;
                    byte[] buffer = new byte[BUFFER_SIZE];

                    while (position < length) {
                        int len = position + BUFFER_SIZE <= length ? BUFFER_SIZE : (int) (length - position);
                        in.readFully(buffer, 0, len);
                        output.writeBytes(buffer, 0, len);
                        position += len;
                    }
                } finally {
                    if (output != null) {
                        output.close();
                    }
                }
            }
        }
    }

}