Simple Tar reader in Java
Posted by: jango on: July 22, 2008
/**
* A simple tar reader
* Just reads through tar file, parses the headers and writes file.
*/
package com.jango.tarreader;
import java.io.IOException;
import java.io.InputStream;
/**
* @author vinu
*
*/
public abstract class AbstractTarReader {
public void read(InputStream in) throws IOException {
while (true) {
Header head = parseHeader(in);
if (head == null)
break;
if (head.isFile && head.filesize > 0) {
int remainder = head.filesize % 512;
int skiplen = 0;
if (remainder != 0)
skiplen = 512 – remainder;
byte[] fileContents = new byte[head.filesize];
in.read(fileContents);
in.skip(skiplen);
createFile(head.filename, fileContents);
} else if (!head.isFile) {
createDir(head.filename);
}
}
}
/**
* Creates the file – dependent on implementation
*
* @param filename
* @param fileContents
* @throws IOException
*/
public abstract void createFile(String filename, byte[] fileContents)
throws IOException;
/**
* Creates the directory as in the tar
*
* @param dirname
*/
public abstract void createDir(String dirname);
// Parses the header
private Header parseHeader(InputStream in) throws IOException {
Header head = new Header();
byte buf[] = new byte[512];
int len = in.read(buf);
// EOF or not fully read
if (len == -1 || len != 512)
return null;
StringBuffer sBufFilename = new StringBuffer();
byte linkIndicator = buf[156];
for (int i = 0; i < 100; i++) {
if (buf[i] != 0) {
sBufFilename.append((char) buf[i]);
}
}
StringBuffer sBufFilesize = new StringBuffer();
for (int i = 124; i < 136; i++) {
sBufFilesize.append((char) buf[i]);
}
head.filename = sBufFilename.toString();
head.filesize = Integer.parseInt(“0″ + sBufFilesize.toString().trim(),8);
if(head.filesize==0 && head.filename.length()==0)
return null;
if ((char) linkIndicator == ’5′) {
head.isFile = false;
}
return head;
}
// To store the header info – Simple for now
// Only the filename
class Header {
String filename;
int filesize;
boolean isFile = true;
}
}
