com.google.appengine.tools.mapreduce.inputs.LineInputStream.java Source code

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Here is the source code for com.google.appengine.tools.mapreduce.inputs.LineInputStream.java

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/*
 * Copyright 2010 Google 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.google.appengine.tools.mapreduce.inputs;

import com.google.common.io.CountingInputStream;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.NoSuchElementException;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * A reader to return one line at a time from an underlying input stream.
 *
 * For internal use only. User code cannot safely depend on this class.
 *
 */
class LineInputStream {

    private static final Logger log = Logger.getLogger(LineInputStream.class.getName());
    private static final int INITIAL_BUFFER_SIZE = 10000;

    private final int separator;
    private final CountingInputStream in;
    private final long lengthToRead;

    LineInputStream(InputStream in, long lengthToRead, byte separator) {
        this.in = new CountingInputStream(in);
        this.lengthToRead = lengthToRead;
        this.separator = (separator & 0xff);
    }

    public byte[] next() {
        try {
            // we are reading one record after lengthToRead because the splits are not assumed to be
            // aligned to separators in the file.
            long recordStart = in.getCount();
            if (recordStart - 1 >= lengthToRead) {
                throw new NoSuchElementException();
            }
            ByteArrayOutputStream tempBuffer = new ByteArrayOutputStream(INITIAL_BUFFER_SIZE);
            copyUntilNextRecord(tempBuffer);
            return tempBuffer.toByteArray();
        } catch (IOException e) {
            log.log(Level.WARNING, "Failed to read next record", e);
            throw new RuntimeException("Failed to read next record", e);
        }
    }

    public long getBytesCount() {
        return in.getCount();
    }

    private void copyUntilNextRecord(OutputStream out) throws IOException {
        int value = in.read();
        if (value == -1) {
            throw new NoSuchElementException();
        }
        while (value != separator && value != -1) {
            out.write(value);
            value = in.read();
        }
    }

    public void close() throws IOException {
        in.close();
    }
}