DZone Snippets: io code

IoPeg

db-keen (db) — Thu, 26 Jun 2008 04:29:42 GMT

This is a direct port of the IoPeg metagrammar (rev 46) as found here: http://iopeg.googlecode.com/svn/trunk/PEG.peg



#  Hierarchical syntax

grammar IoPeg



  rule grammar

    spacing definition+ end_of_file

  end



  rule definition

    identifier leftarrow expression

  end



  rule expression

    sequence (slash sequence)*

  end



  rule sequence

    prefix*

  end



  rule prefix

    (and / not)? suffix

  end



  rule suffix

    primary (question / star / plus)?

  end



  rule primary

    identifier !leftarrow / open expression close / literal / class / dot

  end



  rule identifier

    ident_start ident_cont* spacing

  end



  rule ident_start

    [a-zA-Z_]

  end



  rule ident_cont

    ident_start / [0-9]

  end



  rule literal

    ['] (!['] char)* ['] spacing / ["] (!["] char)* ["] spacing

  end



  rule class

    '[' (!']' range)* ']' spacing

  end



  rule range

    char '-' char / char

  end



  rule char

    "\\" [nrt'"\[\]\\] / "\\" [0-2] [0-7] [0-7] / "\\" [0-7] [0-7]? / !"\\" .

  end



  rule leftarrow

    '<-' spacing

  end



  rule slash

    '/' spacing

  end



  rule and

    '&' spacing

  end



  rule not

    '!' spacing

  end



  rule question

    '?' spacing

  end



  rule star

    '*' spacing

  end



  rule plus

    '+' spacing

  end



  rule open

    '(' spacing

  end



  rule close

    ')' spacing

  end



  rule dot

    '.' spacing

  end



  rule spacing

    (space / comment)*

  end



  rule comment

    '#' (!end_of_line .)* end_of_line

  end



  rule space

    ' ' / "\t" / end_of_line

  end



  rule end_of_line

    "\r\n" / "\n" / "\r"

  end



  rule end_of_file

    !.

  end



end

Speeding up Java I/O - Read method

rick (Rick Ross) — Sat, 17 May 2008 14:49:13 GMT

The following example counts the number of newline bytes ('\n') in a file. It simply uses the read method on a FileInputStream:



 import java.io.*;

  

  public class intro1 {

    public static void main(String args[]) {

      if (args.length != 1) {

        System.err.println("missing filename");

        System.exit(1);

      }

      try {

        FileInputStream fis =

            new FileInputStream(args[0]);

        int cnt = 0;

        int b;

        while ((b = fis.read()) != -1) {

          if (b == '\n')

            cnt++;

        }

        fis.close();

        System.out.println(cnt);

      }

      catch (IOException e) {

        System.err.println(e);

      }

    }

  }

Subject to Sun's Code Sample License

Ruby: Open a file, write to it, and close it in one line

sikelianos (Zeke Sikelianos) — Tue, 29 Jan 2008 18:42:06 GMT

r - Open a file for reading. The file must exist.
w - Create an empty file for writing. If a file with the same name already exists its content is erased and the file is treated as a new empty file.
a - Append to a file. Writing operations append data at the end of the file. The file is created if it does not exist.
r+ - Open a file for update both reading and writing. The file must exist.
w+ - Create an empty file for both reading and writing. If a file with the same name already exists its content is erased and the file is treated as a new empty file.
a+ - Open a file for reading and appending. All writing operations are performed at the end of the file, protecting the previous content to be overwritten. You can reposition (fseek, rewind) the internal pointer to anywhere in the file for reading, but writing operations will move it back to the end of file. The file is created if it does not exist.



File.open(local_filename, 'w') {|f| f.write(doc) }

Loading a text file into a String from the classpath

Archanciel (Jean-Pierre Schnyder) — Thu, 30 Aug 2007 12:48:18 GMT

Locate a text file in the classpath and read it into a String



    /** 

     * @param filePath      name of file to open. The file can reside

     *                      anywhere in the classpath

     */

    private String readFileAsString(String filePath) throws java.io.IOException {

        StringBuffer fileData = new StringBuffer(1000);

        BufferedReader reader = new BufferedReader(new InputStreamReader(this

            .getClass().getClassLoader().getResourceAsStream(filePath)));

        char[] buf = new char[1024];

        int numRead = 0;

        while ((numRead = reader.read(buf)) != -1) {

            String readData = String.valueOf(buf, 0, numRead);

            fileData.append(readData);

            buf = new char[1024];

        }

        reader.close();

        return fileData.toString();

    }

Loading a property file from the classpath

Archanciel (Jean-Pierre Schnyder) — Thu, 30 Aug 2007 12:28:02 GMT

Loads a property file located anywhere in the classpath



    private Properties getPropertiesFromClasspath(String propFileName) throws IOException {

        // loading xmlProfileGen.properties from the classpath

        Properties props = new Properties();

        InputStream inputStream = this.getClass().getClassLoader()

            .getResourceAsStream(propFileName);



        if (inputStream == null) {

            throw new FileNotFoundException("property file '" + propFileName

                + "' not found in the classpath");

        }



        props.load(inputStream);



        return props;

    }

SCGI connector (Java)

ArtemGr (Artem Gr Kozarezov) — Mon, 16 Jul 2007 13:50:45 GMT



import java.io.IOException;

import java.io.InputStream;

import java.nio.ByteBuffer;

import java.nio.charset.Charset;

import java.util.HashMap;



/**

 * SCGI connector.


 * Version: 1.0


 * Home page: http://snippets.dzone.com/posts/show/4304

 */

public class SCGI {

  public static class SCGIException extends IOException {

    private static final long serialVersionUID = 1L;



    public SCGIException(String message) {

      super(message);

    }

  }



  /** Used to decode the headers. */

  public static final Charset ISO_8859_1 = Charset.forName("ISO-8859-1");



  /**

   * Read the SCGI request headers.


   * After the headers had been loaded,

   * you can read the body of the request manually from the same {@code input} stream:
   *   // Load the SCGI headers.

   *   Socket clientSocket = socket.accept();

   *   BufferedInputStream bis = new BufferedInputStream(clientSocket.getInputStream(), 4096);

   *   HashMap env = SCGI.parse(bis);

   *   // Read the body of the request.

   *   bis.read(new byte[Integer.parseInt(env.get("CONTENT_LENGTH"))]);

   * 

   * @param input an efficient (buffered) input stream.

   * @return strings passed via the SCGI request.

   */

  public static HashMap parse(InputStream input) throws IOException {

    StringBuilder lengthString = new StringBuilder(12);

    String headers = "";

    for (;;) {

      char ch = (char) input.read();

      if (ch >= '0' && ch <= '9') {

        lengthString.append(ch);

      } else if (ch == ':') {

        int length = Integer.parseInt(lengthString.toString());

        byte[] headersBuf = new byte[length];

        int read = input.read(headersBuf);

        if (read != headersBuf.length)

          throw new SCGIException("Couldn't read all the headers (" + length + ").");

        headers = ISO_8859_1.decode(ByteBuffer.wrap(headersBuf)).toString();

        if (input.read() != ',') throw new SCGIException("Wrong SCGI header length: " + lengthString);

        break;

      } else {

        lengthString.append(ch);

        throw new SCGIException("Wrong SCGI header length: " + lengthString);

      }

    }

    HashMap env = new HashMap();

    while (headers.length() != 0) {

      int sep1 = headers.indexOf(0);

      int sep2 = headers.indexOf(0, sep1 + 1);

      env.put(headers.substring(0, sep1), headers.substring(sep1 + 1, sep2));

      headers = headers.substring(sep2 + 1);

    }

    return env;

  }

}

"Unget string" function

Minimiscience (Guildorn Tanaleth) — Thu, 05 Jul 2007 03:19:35 GMT

As a complement to ungetc(), this C function pushes a string back onto an input stream, character by character. It returns the number of characters pushed, or -1 if an error occurred.



void ungets(char* str, FILE* stream) {

 if (!str || !file) return -1;

 size_t len = strlen(str);

 for (int i=len-1; i>=0; i--) if (ungetc(str[i], stream) == EOF) return -1;

 return len;

}

Java: File System: Getting the path of TMP directory from Environmental Variable

thitiv (Thiti V. Sintopchai) — Thu, 17 May 2007 10:54:45 GMT



public static String INDEX_FILE_LOCATION = System.getenv("TMP") + File.separator + "dl-index.tmp";

Java: Listing the Files or Subdirectories in a Directory

thitiv (Thiti V. Sintopchai) — Wed, 16 May 2007 03:38:41 GMT

// Ref: Java Developers Almanac
// http://www.exampledepot.com/egs/java.io/GetFiles.html





    //

    // Example 1

    //



    File dir = new File("directoryName");

    

    String[] children = dir.list();

    if (children == null) {

        // Either dir does not exist or is not a directory

    } else {

        for (int i=0; i            // Get filename of file or directory

            String filename = children[i];

        }

    }



    //

    // Example 2

    //

    

    // It is also possible to filter the list of returned files.

    // This example does not return any files that start with '.'

    FilenameFilter filter = new FilenameFilter() {

        public boolean accept(File dir, String name) {

            return !name.startsWith(".");

        }

    };

    children = dir.list(filter);

    

    //

    // Example 3

    //



    

    // The list of files can also be retrieved as File objects

    File[] files = dir.listFiles();



    //

    // Example 4

    //

    

    // This filter only returns directories

    FileFilter fileFilter = new FileFilter() {

        public boolean accept(File file) {

            return file.isDirectory();

        }

    };

    files = dir.listFiles(fileFilter);

Java DOM : Creating an XML Document from XML File

thitiv (Thiti V. Sintopchai) — Mon, 14 May 2007 08:52:42 GMT

// description of your code here



    try

    {

      //

      // Create the XML Document

      //



      DocumentBuilderFactory dbfac = DocumentBuilderFactory.newInstance();

      DocumentBuilder docBuilder = dbfac.newDocumentBuilder();

      Document doc = docBuilder.parse(filePath);



      // ...



    }

    catch (Exception e)

    {

      // ...

    }