programming-examples/java/XML/Byte loader.java

Byte loader

package com.ack.tools.jarinfo;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;
import java.util.Hashtable;
import java.util.zip.ZipEntry;
import java.util.zip.ZipInputStream;

public class ByteLoader {
  private static int kDEFAULT_CHUNK_SIZE = 256;

  /**
   *  Creates a stateless ByteLoader object that loads
   *  bytes from stream, URL and ZipEntry data sources.
   */
  public ByteLoader() {
  }

  /**
   * Loads the specified zentry from the supplied ZipInputStream
   * into a byte array.
   * @param  zip input stream for the archive file
   * @param  the actual zip entry to be read from the stream
   * @return bytes for the zip entry or null if not found in stream
   * @exception java.io.IOException reports any IO problems that occur in the process
   */
  public byte[] loadBytesFromZipEntry( ZipInputStream zin, ZipEntry zentry )
      throws IOException {
    byte[] b = null;
    if( !zentry.isDirectory() ) {
      ZipEntry ze;
      String zname = zentry.getName();
      while( ( ze = zin.getNextEntry() ) != null ) {
        if( zname.equals( ze.getName() ) ) {
          int size = (int) zentry.getSize();
          if( size == -1 )
            throw new IOException( "zipentry has unspecified size -> " + zname );
          b = loadBytesFromStreamForSize( zin, size );
          break;
        }
      }
    }
    return b;
  }

  /**
   * A convenience method for loading a collection of ZipEntrys from
   * the supplied ZipInputStream.
   *
   * @param input stream for the archive file to be searched
   * @param table of resource names mapped against their ZipEntry
   * @return the resource names mapped against their byte arrays
   * @exception java.io.IOException reports io errors that occurred during processing
   */
  public Hashtable loadBytesFromZipEntries( ZipInputStream zin, Hashtable zipEntries )
      throws IOException {
    Hashtable resultTable = new Hashtable();
    IOException iofailure = null;
    if( zipEntries.size() > 0 ) {
      try {
        ZipEntry ze;
        byte[] b;
        int size;

        while( ( ze = zin.getNextEntry() ) != null ) {
          if( !ze.isDirectory() ) {
            String zname = ze.getName();
            if( zipEntries.containsKey( zname ) ) {
              ze = (ZipEntry) zipEntries.get( zname );
              if( ( size = (int) ze.getSize() ) != -1 ) {
                try {
                  if( ( b = loadBytesFromStreamForSize( zin, size ) ) != null )
                    resultTable.put( zname, b );
                }
                catch( IOException ioe ) {
                  iofailure = ioe;
                }
              }
            }
          }
        }
      }
      catch( IOException ioe ) {
        iofailure = ioe;
      }
    }

    if( iofailure != null )
      throw iofailure;

    return resultTable;
  }

  /**
   * Load an array of bytes from the supplied url data source
   *
   * @param the url to load the bytes from
   * @return bytes from the url
   * @exception java.io.IOException reports io errors occurring during the method
   */
  public byte[] loadBytesFromURL( URL url ) throws IOException {
    byte[] b = null;
    URLConnection con = url.openConnection();
    int size = con.getContentLength();
    InputStream in = null;

    try {
      if( ( in = con.getInputStream() ) != null )
        b = ( size != -1 ) ? loadBytesFromStreamForSize( in, size ) : loadBytesFromStream( in );
    }
    finally {
      if( in != null )
        try {
          in.close();
        }
        catch( IOException ioe ) {
        }
    }
    return b;
  }

  /**
   * Loads the supplied number bytes from the given input stream
   *
   * @param stream to read the bytes from
   * @param the number of bytes to read
   * @return bytes read from the stream
   * @exception java.io.IOException reports IO failures
   */
  public byte[] loadBytesFromStreamForSize( InputStream in, int size )
      throws IOException {
    int count, index = 0;
    byte[] b = new byte[size];

    // read in the bytes from input stream
    while( ( count = in.read( b, index, size ) ) > 0 ) {
      size -= count;
      index += count;
    }
    return b;
  }

  /**
   * Loads bytes from the given input stream until the end of stream
   * is reached.  It reads in at kDEFAULT_CHUNK_SIZE chunks.
   *
   * @param stream to read the bytes from
   * @return bytes read from the stream
   * @exception java.io.IOException reports IO failures
   */
  public byte[] loadBytesFromStream( InputStream in ) throws IOException {
    return loadBytesFromStream( in, kDEFAULT_CHUNK_SIZE );
  }

  /**
   * Loads bytes from the given input stream until the end of stream
   * is reached.  Bytes are read in at the supplied <code>chunkSize</code>
   * rate.
   *
   * @param stream to read the bytes from
   * @return bytes read from the stream
   * @exception java.io.IOException reports IO failures
   */
  public byte[] loadBytesFromStream( InputStream in, int chunkSize )
      throws IOException {
    if( chunkSize < 1 )
      chunkSize = kDEFAULT_CHUNK_SIZE;

    int count;
    ByteArrayOutputStream bo = new ByteArrayOutputStream();
    byte[] b = new byte[chunkSize];
    try {
      while( ( count = in.read( b, 0, chunkSize ) ) > 0 )
        bo.write( b, 0, count );
      byte[] thebytes = bo.toByteArray();
      return thebytes;
    }
    finally {
      bo.close();
      bo = null;
    }
  }
}