com.kolich.common.util.io.JumpToLine.java Source code

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Here is the source code for com.kolich.common.util.io.JumpToLine.java

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/**
 * Copyright (c) 2015 Mark S. Kolich
 * http://mark.koli.ch
 *
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use,
 * copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following
 * conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */

package com.kolich.common.util.io;

import static com.kolich.common.DefaultCharacterEncoding.UTF_8;
import static org.apache.commons.io.IOUtils.lineIterator;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.NoSuchElementException;

import org.apache.commons.io.IOUtils;
import org.apache.commons.io.LineIterator;

public final class JumpToLine {

    private final InputStream is_;
    private final String charsetName_;

    private final LineIterator it_;

    private long lastLineRead_ = -1L;

    /**
     * Opens any underlying streams/readers and immeadietly seeks
     * to the line in the file that's next to be read; skipping over
     * lines in the file this reader has already read.
     */
    public JumpToLine(final InputStream is, final String charsetName) throws IOException {
        is_ = is;
        charsetName_ = charsetName;
        lastLineRead_ = 1L;
        try {
            it_ = lineIterator(is_, charsetName_);
        } catch (IOException e) {
            close();
            throw e;
        }
    }

    public JumpToLine(final InputStream is) throws IOException {
        this(is, UTF_8);
    }

    public JumpToLine(final File file, final String charsetName) throws IOException {
        this(new FileInputStream(file), charsetName);
    }

    public JumpToLine(final File file) throws IOException {
        this(file, UTF_8);
    }

    /**
     * Seeks to the last line read in the file.
     */
    public long seek() {
        return seek(lastLineRead_);
    }

    /**
     * Seeks to a given line number in the stream/file.
     * @param line the line number to seek to
     */
    public long seek(final long line) {
        long lineCount = 1L;
        while ((it_ != null) && (it_.hasNext()) && (lineCount < line)) {
            it_.nextLine();
            lineCount += 1L;
        }
        // If we got to the end of the file, but haven't read as many
        // lines as we should have, then the requested line number is
        // out of range.
        if (lineCount < line) {
            throw new NoSuchElementException("Invalid line number; " + "out of range.");
        }
        lastLineRead_ = lineCount;
        return lineCount;
    }

    /**
     * Closes this IOUtils LineIterator and the underlying
     * input stream reader.
     */
    public void close() {
        IOUtils.closeQuietly(is_);
        LineIterator.closeQuietly(it_);
    }

    /**
     * Returns true of there are any more lines to read in the
     * file.  Otherwise, returns false.
     * @return
     */
    public boolean hasNext() {
        return it_.hasNext();
    }

    /**
     * Read a line of text from this reader.
     * @return
     */
    public String readLine() {
        String ret = null;
        try {
            // If there is nothing more to read with this LineIterator
            // then nextLine() throws a NoSuchElementException.
            ret = it_.nextLine();
            lastLineRead_ += 1L;
        } catch (NoSuchElementException e) {
            throw e;
        }
        return ret;
    }

    public long getLastLineRead() {
        return lastLineRead_;
    }

}