Bad file descriptor?{resolved}

Does anyone know what this might mean? I am trying to calculate a message digest for a stream but a java.io.Exception: Bad file descriptor keeps getting thrown. :confused:

What kind of stream?

DigestInputStream.

Wrapped around what? A SocketInputStream?

The message sounds a bit like a cryptic way of saying "network connection lost", or maybe "no data currently available".

I was able to get things to work but im not quite sure if the output produced from the code is correct. Run this on a directory and see what you get.

Code:

---


 import java.security.*;
 import java.io.*;
 
 class Digest{

  FileInputStream fis;
  private MessageDigest md;
  private DigestInputStream dis;
  private BufferedOutputStream bis;
  private byte[] digest;
  private File[] files;
  private int bytesread;
  private byte[] buffer; 
 
  public Digest(File[] files){
  this.files = files;
  } 

  public void calDigest() throws IOException, NoSuchAlgorithmException{

    for(int i = 0; i < files.length; i++){
    md = MessageDigest.getInstance("SHA");
    fis = new FileInputStream(files[i]); 
    dis = new DigestInputStream(fis, md);
    buffer = new byte[(byte)files[i].length()];
    while((bytesread = dis.read(buffer)) != -1) 
    digest = dis.getMessageDigest().digest();
    System.out.println(files[i].getName() + ": " + digest);   
    System.out.println();
   
  } 
  }
 }

 public class DigestTest{
    public static void main(String[] args){
   
  File dir = new File(args[0]);
    if(args.length == 0){
      System.out.println("Usage: You must specify arguemets!"); 
      System.exit(0);
    }
    if(!dir.isDirectory()){
      System.out.println("Usage: You must specify a directory!"); 
      System.exit(0);
    }
   
    File[] files = dir.listFiles();
    Digest digest = new Digest(files);
    try{ 
    digest.calDigest();
    }catch(IOException e){
        System.err.println(e);
    }
    catch(NoSuchAlgorithmException nsa){
      System.err.println(nsa);
      }
    }
  }

---

You can't just pass a byte array to println, but aside from that it seems to be working. I have no means to check the digest though, but why should it be wrong?
I adjusted the code slightly, but I still get IOExceptions when the thing tries to digest a directory.

Code:

---

import java.security.*;
import java.io.*;

class Digest{

        FileInputStream fis;
        private MessageDigest md;
        private DigestInputStream dis;
        private BufferedOutputStream bis;
        private byte[] digest;
        private File[] files;
        private int bytesread;
        private byte[] buffer;

        public Digest(File[] files){
                this.files = files;
        }

        public void calDigest() throws IOException, NoSuchAlgorithmException{
                buffer = new byte[1024];
                for(int i = 0; i < files.length; i++){
                        md = MessageDigest.getInstance("SHA");
                        fis = new FileInputStream(files[i]);
                        dis = new DigestInputStream(fis, md);
                        while((bytesread = dis.read(buffer)) != -1)
                        digest = dis.getMessageDigest().digest();
                        System.out.println(files[i].getName() + ": ");
                        writeDigest();
                        System.out.println();
                        System.out.flush();
                }
        }

        private void writeDigest() {
                int l = digest.length;
                for(int i = 0; i < l; ++i) {
                        try {
                        System.out.print(Integer.toHexString(digest[i]).substring(0,2) + " ");
                        } catch(Exception e) {
                        }
                }
        }
}

public class DigestTest{
        public static void main(String[] args){
       
                if(args.length == 0){
                        System.out.println("Usage: You must specify arguments!"); 
                        System.exit(0);
                }
                File dir = new File(args[0]);
                if(!dir.isDirectory()){
                        System.out.println("Usage: You must specify a directory!"); 
                        System.exit(0);
                }
               
                File[] files = dir.listFiles();
                Digest digest = new Digest(files);
                try{ 
                        digest.calDigest();
                }catch(IOException e){
                        System.err.println(e);
                }catch(NoSuchAlgorithmException nsa){
                        System.err.println(nsa);
                }
        }
}

---

I forgot a byte[] array cannot be passed. :blush: The writeDigest() method was exactly what was needed. Thanks. Yeah i didnt account for directories within directories but thats ok. Thanks for the help.

BTW you need to refine writeDigest. Currently it just skips bytes where the most significant nibble is 0 (anything from 00 to 0F). This is because they are converted to the strings '' to 'F' and substring throws a StringIndexOutOfBoundsException.

Im not too sure if i follow your use of substring. I used a StringBuffer instead and it seems to work pretty good.

Code:

---

private void writeDigest(String file) {
  StringBuffer sb = new StringBuffer(file);
  sb.append(":");
  for(int i = 0; i < digest.length; ++i) {
    sb.append(digest[i] + " ");
  }       
  System.out.println(sb);
}

---

Thanks for the help.