com.cloudera.crunch.io.text.TextFileReaderFactory.java Source code

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Here is the source code for com.cloudera.crunch.io.text.TextFileReaderFactory.java

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/**
 * Copyright (c) 2011, Cloudera, Inc. All Rights Reserved.
 *
 * Cloudera, Inc. 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
 *
 * This software 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.cloudera.crunch.io.text;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Iterator;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;

import com.cloudera.crunch.MapFn;
import com.cloudera.crunch.fn.CompositeMapFn;
import com.cloudera.crunch.fn.IdentityFn;
import com.cloudera.crunch.io.FileReaderFactory;
import com.cloudera.crunch.type.PType;
import com.google.common.collect.Iterators;
import com.google.common.collect.UnmodifiableIterator;

public class TextFileReaderFactory<T> implements FileReaderFactory<T> {

    private static final Log LOG = LogFactory.getLog(TextFileReaderFactory.class);

    private final PType<T> ptype;

    public TextFileReaderFactory(PType<T> ptype) {
        this.ptype = ptype;
    }

    @Override
    public Iterator<T> read(FileSystem fs, Path path) {
        MapFn mapFn = null;
        if (String.class.equals(ptype.getTypeClass())) {
            mapFn = IdentityFn.getInstance();
        } else {
            // Check for a composite MapFn for the PType.
            // Note that this won't work for Avro-- need to solve that.
            MapFn input = ptype.getInputMapFn();
            if (input instanceof CompositeMapFn) {
                mapFn = ((CompositeMapFn) input).getSecond();
            }
        }
        mapFn.initialize();

        FSDataInputStream is = null;
        try {
            is = fs.open(path);
        } catch (IOException e) {
            LOG.info("Could not read path: " + path, e);
            return Iterators.emptyIterator();
        }

        final BufferedReader reader = new BufferedReader(new InputStreamReader(is));
        final MapFn<String, T> iterMapFn = mapFn;
        return new UnmodifiableIterator<T>() {
            private String nextLine;

            @Override
            public boolean hasNext() {
                try {
                    return (nextLine = reader.readLine()) != null;
                } catch (IOException e) {
                    LOG.info("Exception reading text file stream", e);
                    return false;
                }
            }

            @Override
            public T next() {
                return iterMapFn.map(nextLine);
            }
        };
    }
}