Sunday, April 13, 2014

There are many different way to do this. You might write your own once you figure out what has to be done exactly. But I came up with this. Additionally I wanted the input to be numeric as well. So below is what I came up with.
private class NumericAndLengthFilter extends DocumentFilter {

        /**
         * Number of characters allowed.
         */
        private int length = 0;

        /**
         * Restricts the number of charcacters can be entered by given length.
         * @param length Number of characters allowed.
         */
        public NumericAndLengthFilter(int length) {
            this.length = length;
        }

        @Override
        public void insertString(FilterBypass fb, int offset, String string,
                AttributeSet attr) throws
                BadLocationException {
            if (isNumeric(string)) {
                if (this.length > 0 && fb.getDocument().getLength() + string.
                        length()
                        > this.length) {
                    return;
                }
                super.insertString(fb, offset, string, attr);
            }
        }

        @Override
        public void replace(FilterBypass fb, int offset, int length, String text,
                AttributeSet attrs) throws
                BadLocationException {
            if (isNumeric(text)) {
                if (this.length > 0 && fb.getDocument().getLength() + text.
                        length()
                        > this.length) {
                    return;
                }
                super.insertString(fb, offset, text, attrs);
            }
        }

        /**
         * This method tests whether given text can be represented as number.
         * This method can be enhanced further for specific needs.
         * @param text Input text.
         * @return {@code true} if given string can be converted to number; otherwise returns {@code false}.
         */
        private boolean isNumeric(String text) {
            if (text == null || text.trim().equals("")) {
                return false;
            }
            for (int iCount = 0; iCount < text.length(); iCount++) {
                if (!Character.isDigit(text.charAt(iCount))) {
                    return false;
                }
            }
            return true;
        }
    }
}

Friday, April 11, 2014

This time I came across a slightly different way than extending the documentfilter. That is I will write my own plain document here.
class IntegerRangeDocument extends PlainDocument {

  int minimum, maximum;

  int currentValue = 0;

  public IntegerRangeDocument(int minimum, int maximum) {
    this.minimum = minimum;
    this.maximum = maximum;
  }

  public int getValue() {
    return currentValue;
  }

  public void insertString(int offset, String string, AttributeSet attributes)
      throws BadLocationException {

    if (string == null) {
      return;
    } else {
      String newValue;
      int length = getLength();
      if (length == 0) {
        newValue = string;
      } else {
        String currentContent = getText(0, length);
        StringBuffer currentBuffer = new StringBuffer(currentContent);
        currentBuffer.insert(offset, string);
        newValue = currentBuffer.toString();
      }
      try {
        currentValue = checkInput(newValue);
        super.insertString(offset, string, attributes);
      } catch (Exception exception) {
        Toolkit.getDefaultToolkit().beep();
      }
    }
  }

  public void remove(int offset, int length) throws BadLocationException {
    int currentLength = getLength();
    String currentContent = getText(0, currentLength);
    String before = currentContent.substring(0, offset);
    String after = currentContent.substring(length + offset, currentLength);
    String newValue = before + after;
    try {
      currentValue = checkInput(newValue);
      super.remove(offset, length);
    } catch (Exception exception) {
      Toolkit.getDefaultToolkit().beep();
    }
  }

  public int checkInput(String proposedValue) throws NumberFormatException {
    int newValue = 0;
    if (proposedValue.length() > 0) {
      newValue = Integer.parseInt(proposedValue);
    }
    if ((minimum <= newValue) && (newValue <= maximum)) {
      return newValue;
    } else {
      throw new NumberFormatException();
    }
  }
}
Now you can attach your text field with this plain document as below to achieve our requirement.

Document rangeOne = new IntegerRangeDocument(0, 255);
JTextField textFieldOne = new JTextField();
textFieldOne.setDocument(rangeOne);
    

Thursday, April 10, 2014

This is slightly opposite to what we have seen  in one of the previous posts
Please use the below DocumentFilter for the same.


class MyDocFilter extends DocumentFilter {
   private static final String REMOVE_REGEX = "\\d";
   private boolean filter = true;

   public boolean isFilter() {
      return filter;
   }

   public void setFilter(boolean filter) {
      this.filter = filter;
   }

   @Override
   public void insertString(FilterBypass fb, int offset, String text,
         AttributeSet attr) throws BadLocationException {
      if (filter) {
         text = text.replaceAll(REMOVE_REGEX, "");
      }
      super.insertString(fb, offset, text, attr);

   }

   @Override
   public void replace(FilterBypass fb, int offset, int length, String text,
         AttributeSet attrs) throws BadLocationException {
      if (filter) {
         text = text.replaceAll(REMOVE_REGEX, "");
      }
      super.replace(fb, offset, length, text, attrs);

   }
}
I have read a lot for this and the best way I found to do this is by extending the DocumentFilter class and using this new DocumentFilter
class MyIntFilter extends DocumentFilter {
   @Override
   public void insertString(FilterBypass fb, int offset, String string,
         AttributeSet attr) throws BadLocationException {

      Document doc = fb.getDocument();
      StringBuilder sb = new StringBuilder();
      sb.append(doc.getText(0, doc.getLength()));
      sb.insert(offset, string);

      if (test(sb.toString())) {
         super.insertString(fb, offset, string, attr);
      } else {
         // warn the user and don't allow the insert
      }
   }

   private boolean test(String text) {
      try {
         Integer.parseInt(text);
         return true;
      } catch (NumberFormatException e) {
         return false;
      }
   }

   @Override
   public void replace(FilterBypass fb, int offset, int length, String text,
         AttributeSet attrs) throws BadLocationException {

      Document doc = fb.getDocument();
      StringBuilder sb = new StringBuilder();
      sb.append(doc.getText(0, doc.getLength()));
      sb.replace(offset, offset + length, text);

      if (test(sb.toString())) {
         super.replace(fb, offset, length, text, attrs);
      } else {
         // warn the user and don't allow the insert
      }

   }

   @Override
   public void remove(FilterBypass fb, int offset, int length)
         throws BadLocationException {
      Document doc = fb.getDocument();
      StringBuilder sb = new StringBuilder();
      sb.append(doc.getText(0, doc.getLength()));
      sb.delete(offset, offset + length);

      if (test(sb.toString())) {
         super.remove(fb, offset, length);
      } else {
         // warn the user and don't allow the insert
      }

   }
}
Now after this use this filter with your JtextField like below:
PlainDocument doc = (PlainDocument) textField.getDocument();
doc.setDocumentFilter(new MyIntFilter());
I recently started working on Java and so from now on I would like to share all the interesting things that I have come across about this beautiful programming language. So I am starting a new tag by name JAVA in this blog which will direct all the posts related to java. Happy coding to myself and all.

Tuesday, March 11, 2014

I have a list of strings in a file separated by a new line.
for example:
input.txt
temp1
temp2
temp3
Now I have a directory with multiple dat files like:
>ls -1 *.dat
one.dat
two.dat
three.dat
And many more dat like like above with random names. Now I want to search for all the strings in input.txt in all the dat files present in  directory(let's say current working directory).This is what I came up with:
create a perl script given below and name it as anything you wish(I named here as temp.pl).place the file input.txt in the current working directory.
#!/usr/bin/perl -w

open (INP,"input.txt") or die $!;
while(<INP>)
{
my $cmd="find . -name \"*.dat\"|xargs grep -w -i $_";
my $output=`$cmd`;
 if($output!~/^\s*$/)
 {
 print $_."\n";
 print "------------------\n";
 print $output."\n";
 print "-------------------\n";
 }
}
exit;
Run this script as :
>./temp.pl
This solved my need.I hope it solves yours too :)

Monday, February 17, 2014

Below is a implementation of Graph Data Structure in C++ as Adjacency List.

I have used STL vector for representation of vertices and STL pair for denoting edge and destination vertex.



struct vertex{
 typedef pair ve;
 vector adj; //cost of edge, destination vertex
 string name;
 vertex(string s)
 {
  name=s;
 }
};

class graph
{
 public:
  typedef map vmap;
  vmap work;
  void addvertex(const string&);
  void addedge(const string& from, const string& to, double cost);
};

void graph::addvertex(const string &name)
{
 vmap::iterator itr=work.begin();
 itr=work.find(name);
 if(itr==work.end())
 {
  vertex *v;
  v= new vertex(name);
  work[name]=v;
  return;
 }
  cout<<"\nVertex already exists!";
}

void graph::addedge(const string& from, const string& to, double cost)
{
 vertex *f=(work.find(from)->second);
 vertex *t=(work.find(to)->second);
 pair edge = make_pair(cost,t);
 f->adj.push_back(edge);
}

Friday, November 29, 2013

There are lot of ways where one can identify memory leaks and lots of blogs and materieals
are available to help a designer to identify the same.

Some say using dbx and others say use mdb or gdb. I agree that all those tools will be useful, but it takes a lot of effort for understanding as well as putting it to work takes some time.

I have thought to break the legacy rules and do something new with the knowledge that
I have on various tools of solaris. So I thought of giving it a try to use tools like
dtrace, perl, ps command etc along with c++.

Putting this toll to action is an effort less job.

I am happy to have created a tool which I think would be very use for any solaris unix programmer.
This tool will give the list of all memory leaks of a process running in the background.

It uses dtrace to identify the memory allocations,
It uses the ps command to identify the memory used by a process.
It uses perl to filter and generate reports of meory leaks.

Main functionalities of this tool are:

  • Generate a report which contains actual physical memory used by the process, Virtual memory used, % of cpu used and %memory used.
  • Generate a report which contains all the memory leaks of the process due to inefficient coding techniques.
  • Generate a separate report for each and every process.

I have tested this on:
SunOS 5.10 Generic_147440-27 sun4u sparc SUNW,SPARC-Enterprise

Thanks to Frederic, I have taken part of his logic written in his blog:

You can download the zip file from the link here:

The file name is cpuleaks.gz.
Unzip this file using gzip -d cpuleaks.gz and you can place it on any server and give the execute permissions and run this process as a root user(dtrace can be run only using root access on my server. If dtrace can be used by a user other than root, well and fine).

Execution of the process should be as below:
 

cpuleaks <comma separated pid list> -st <time interval for mem usage>
 
ex: cpuleaks 1234,2341 -st 2

This above command will give 4 files as output after either the processes 1234,2341 complete or if you press CTRL +C(an interrupt signal).
1234.cpumem
1234.leaks
2341.cpumem
2341.leaks

 
where
  • .leaks report will have the list of all memory leaks
  • .cpumem report will have the memory usage of the process for every interval passed as an argument to the cpuleaks binary.

Thursday, September 5, 2013

One of my colleagues asked this query to me. And I liked the query very much.
So I started thinking about that.
For example i have a below file:
1 name1
2 name2
3 name3
4 name1
5 name4
6 name2
7 name1
Now i want to find strings in the file , lets say in the order name1, name2, name3, name4.
And i also want the output to be in the same order in the way i searched as below:
1 name1
4 name1
7 name1
2 name2
6 name2
3 name3
5 name4
Obviously we cannot do this with a single grep command without any temporary files being created.
So I thought perl would be a better option for this. So I came up with a simple perl solution.
perl -lne '/name1/?push @a,$_:
          (/name2/?push @b,$_:
          (/name3/?push @c,$_:
           /name4/?push @d,$_:next));
          END{print join "\n",@a,@b,@c,@d}' your_file

And this worked like a a charm.

Monday, September 2, 2013

We'll start with a brief refresher on the basics of perl one-liners before we begin. The core of any perl one-liner is the -e switch, which lets you pass a snippet of code on the command-line:perl -e 'print "hi\n"' prints "hi" to the console.
The second standard trick to perl one-liners are the -n and -p flags. Both of these make perl put an implicit loop around your program, running it once for each line of input, with the line in the $_ variable. -p also adds an implicit print at the end of each iteration.
Both of these use perl's special "ARGV" magic file handle internally. What this means is that if there are any files listed on the command-line after your -e, perl will loop over the contents of the files, one at a time. If there aren't any, it will fall back to looping over standard input.
perl -ne 'print if /foo/' acts a lot like grep foo, and perl -pe 's/foo/bar/' replaces foo with bar
Most of the rest of these tricks assume you're using either -n or -p, so I won't mention it every time.

The top 10 one-liner tricks

One Liner-1:   -l
Smart newline processing. Normally, perl hands you entire lines, including a trailing newline. With -l, it will strip the trailing newline off of any lines read, and automatically add a newline to anything you print (including via -p).
Suppose I wanted to strip trailing whitespace from a file. I might naïvely try something like
perl -pe 's/\s*$//'
The problem, however, is that the line ends with "\n", which is whitespace, and so that snippet will also remove all newlines from my file! -l solves the problem, by pulling off the newline before handing my script the line, and then tacking a new one on afterwards:
perl -lpe 's/\s*$//'

One Liner-2: -0
Occasionally, it's useful to run a script over an entire file, or over larger chunks at once. -0 makes -n and -p feed you chunks split on NULL bytes instead of newlines. This is often useful for, e.g. processing the output of find -print0. Furthermore, perl -0777 makes perl not do any splitting, and pass entire files to your script in $_.
find . -name '*~' -print0 | perl -0ne unlink
Could be used to delete all ~-files in a directory tree, without having to remember how xargs works.
One Liner-3: -i
-i tells perl to operate on files in-place. If you use -n or -p with -i, and you pass perl filenames on the command-line, perl will run your script on those files, and then replace their contents with the output. -i optionally accepts an backup suffix as argument; Perl will write backup copies of edited files to names with that suffix added.
perl -i.bak -ne 'print unless /^#/' script.sh
Would strip all whole-line commands from script.sh, but leave a copy of the original in script.sh.bak.
One Liner-4: The .. operator
Perl's .. operator is a stateful operator -- it remembers state between evaluations. As long as its left operand is false, it returns false; Once the left hand returns true, it starts evaluating the right-hand operand until that becomes true, at which point, on the next iteration it resets to false and starts testing the other operand again.
What does that mean in practice? It's a range operator: It can be easily used to act on a range of lines in a file. For instance, I can extract all GPG public keys from a file using:
perl -ne 'print if /-----BEGIN PGP PUBLIC KEY BLOCK-----/../-----END PGP PUBLIC KEY BLOCK-----/' FILE
One Liner-5: -a
-a turns on autosplit mode – perl will automatically split input lines on whitespace into the @F array. If you ever run into any advice that accidentally escaped from 1980 telling you to use awk because it automatically splits lines into fields, this is how you use perl to do the same thing without learning another, even worse, language.
As an example, you could print a list of files along with their link counts using
ls -l | perl -lane 'print "$F[7] $F[1]"'

One Liner-6: -F
-F is used in conjunction with -a, to choose the delimiter on which to split lines. To print every user in /etc/passwd (which is colon-separated with the user in the first column), we could do:
perl -F: -lane 'print $F[0]' /etc/passwd
One Liner-7: \K
\K is undoubtedly my favorite little-known-feature of Perl regular expressions. If \K appears in a regex, it causes the regex matcher to drop everything before that point from the internal record of "Which string did this regex match?". This is most useful in conjunction with s///, where it gives you a simple way to match a long expression, but only replace a suffix of it.
Suppose I want to replace the From: field in an email. We could write something like
perl -lape 's/(^From:).*/$1 Nelson Elhage <nelhage\@ksplice.com>/'
But having to parenthesize the right bit and include the $1 is annoying and error-prone. We can simplify the regex by using \K to tell perl we won't want to replace the start of the match:
perl -lape 's/^From:\K.*/ Nelson Elhage <nelhage\@ksplice.com>/'
One Liner-8: $ENV{}
When you're writing a one-liner using -e in the shell, you generally want to quote it with ', so that dollar signs inside the one-liner aren't expanded by the shell. But that makes it annoying to use a ' inside your one-liner, since you can't escape a single quote inside of single quotes, in the shell.
Let's suppose we wanted to print the username of anyone in /etc/passwd whose name included an apostrophe. One option would be to use a standard shell-quoting trick to include the ':
perl -F: -lane 'print $F[0] if $F[4] =~ /'"'"'/' /etc/passwd
But counting apostrophes and backslashes gets old fast. A better option, in my opinion, is to use the environment to pass the regex into perl, which lets you dodge a layer of parsing entirely:
env re="'" perl -F: -lane 'print $F[0] if $F[4] =~ /$ENV{re}/' /etc/passwd
We use the env command to place the regex in a variable called re, which we can then refer to from the perl script through the %ENV hash. This way is slightly longer, but I find the savings in counting backslashes or quotes to be worth it, especially if you need to end up embedding strings with more than a single metacharacter.
One Liner-9: BEGIN and END
BEGIN { ... } and END { ... } let you put code that gets run entirely before or after the loop over the lines.
For example, I could sum the values in the second column of a CSV file using:
perl -F, -lane '$t += $F[1]; END { print $t }'
One Liner-10: -MRegexp::Common
Using -M on the command line tells perl to load the given module before running your code. There are thousands of modules available on CPAN, numerous of them potentially useful in one-liners, but one of my favorite for one-liner use is Regexp::Common, which, as its name suggests, contains regular expressions to match numerous commonly-used pieces of data.
The full set of regexes available in Regexp::Common is available in its documentation, but here's an example of where I might use it:
Neither the ifconfig nor the ip tool that is supposed to replace it provide, as far as I know, an easy way of extracting information for use by scripts. The ifdata program provides such an interface, but isn't installed everywhere. Using perl and Regexp::Common, however, we can do a pretty decent job of extracing an IP from ip's output:
ip address list eth0 | \

  perl -MRegexp::Common -lne 'print $1 if /($RE{net}{IPv4})/'
So, those are my favorite tricks, but I always love learning more. What tricks have you found or invented for messing with perl on the command-line? What's the most egregious perl "one-liner" you've wielded, continuing to tack on statements well after the point where you should have dropped your code into a real script?