Mega Code Archive
This program computes the CRC checksum of a file
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/*
This program is a part of the companion code for Core Java 8th ed.
(http://horstmann.com/corejava)
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.RandomAccessFile;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.util.zip.CRC32;
/**
* This program computes the CRC checksum of a file. <br>
* Usage: java NIOTest filename
* @version 1.01 2004-05-11
* @author Cay Horstmann
*/
public class NIOTest
{
public static long checksumInputStream(String filename) throws IOException
{
InputStream in = new FileInputStream(filename);
CRC32 crc = new CRC32();
int c;
while ((c = in.read()) != -1)
crc.update(c);
return crc.getValue();
}
public static long checksumBufferedInputStream(String filename) throws IOException
{
InputStream in = new BufferedInputStream(new FileInputStream(filename));
CRC32 crc = new CRC32();
int c;
while ((c = in.read()) != -1)
crc.update(c);
return crc.getValue();
}
public static long checksumRandomAccessFile(String filename) throws IOException
{
RandomAccessFile file = new RandomAccessFile(filename, "r");
long length = file.length();
CRC32 crc = new CRC32();
for (long p = 0; p < length; p++)
{
file.seek(p);
int c = file.readByte();
crc.update(c);
}
return crc.getValue();
}
public static long checksumMappedFile(String filename) throws IOException
{
FileInputStream in = new FileInputStream(filename);
FileChannel channel = in.getChannel();
CRC32 crc = new CRC32();
int length = (int) channel.size();
MappedByteBuffer buffer = channel.map(FileChannel.MapMode.READ_ONLY, 0, length);
for (int p = 0; p < length; p++)
{
int c = buffer.get(p);
crc.update(c);
}
return crc.getValue();
}
public static void main(String[] args) throws IOException
{
System.out.println("Input Stream:");
long start = System.currentTimeMillis();
long crcValue = checksumInputStream(args[0]);
long end = System.currentTimeMillis();
System.out.println(Long.toHexString(crcValue));
System.out.println((end - start) + " milliseconds");
System.out.println("Buffered Input Stream:");
start = System.currentTimeMillis();
crcValue = checksumBufferedInputStream(args[0]);
end = System.currentTimeMillis();
System.out.println(Long.toHexString(crcValue));
System.out.println((end - start) + " milliseconds");
System.out.println("Random Access File:");
start = System.currentTimeMillis();
crcValue = checksumRandomAccessFile(args[0]);
end = System.currentTimeMillis();
System.out.println(Long.toHexString(crcValue));
System.out.println((end - start) + " milliseconds");
System.out.println("Mapped File:");
start = System.currentTimeMillis();
crcValue = checksumMappedFile(args[0]);
end = System.currentTimeMillis();
System.out.println(Long.toHexString(crcValue));
System.out.println((end - start) + " milliseconds");
}
}
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