utils.java

实现如何用java读dbase库的

/*
 	Utils
  Class for contining utility functions.

  This file is part of JavaDBF packege.

  author: [e-mail]
  license: LGPL (http://www.gnu.org/copyleft/lesser.html)

  $Id: Utils.java,v 1.7 2004/03/31 16:00:34 anil Exp $
*/
package com.linuxense.javadbf;

import java.io.*;
import java.util.*;
import java.text.*;

/**
	Miscelaneous functions required by the JavaDBF package.
*/
public final class Utils {

	public static final int ALIGN_LEFT = 10;
	public static final int ALIGN_RIGHT = 12;

	private Utils(){}

	public static int readLittleEndianInt( DataInput in)
	throws IOException {

		int bigEndian = 0;
		for( int shiftBy=0; shiftBy<32; shiftBy+=8) {

			bigEndian |= (in.readUnsignedByte()&0xff) << shiftBy;
		}

		return bigEndian;
	}

	public static short readLittleEndianShort( DataInput in)
	throws IOException {

		int low = in.readUnsignedByte() & 0xff;
		int high = in.readUnsignedByte();

		return (short )(high << 8 | low); 
	}

	public static byte[] trimLeftSpaces( byte [] arr) {

		StringBuffer t_sb = new StringBuffer( arr.length);

		for( int i=0; i<arr.length; i++) {

			if( arr[i] != ' ') {

				t_sb.append( (char)arr[ i]);
			}
		}

		return t_sb.toString().getBytes();
	}

	public static short littleEndian( short value) {

		short num1 = value;
		short mask = (short)0xff;

		short num2 = (short)(num1&mask);
		num2<<=8;
		mask<<=8;

		num2 |= (num1&mask)>>8;

		return num2;
	}

	public static int littleEndian(int value) {

		int num1 = value;
		int mask = 0xff;
		int num2 = 0x00;

		num2 |= num1 & mask;

		for( int i=1; i<4; i++) {

			num2<<=8;
			mask <<= 8;
			num2 |= (num1 & mask)>>(8*i);
		}

		return num2;
	}
	
	public static byte[] textPadding( String text, String characterSetName, int length) throws java.io.UnsupportedEncodingException {

		return textPadding( text, characterSetName, length, Utils.ALIGN_LEFT);
	}

	public static byte[] textPadding( String text, String characterSetName, int length, int alignment) throws java.io.UnsupportedEncodingException {

		return textPadding( text, characterSetName, length, alignment, (byte)' ');
	}

	public static byte[] textPadding( String text, String characterSetName, int length, int alignment,
	byte paddingByte) throws java.io.UnsupportedEncodingException {

		if( text.length() >= length) {

			return text.substring( 0, length).getBytes( characterSetName);
		}

		byte byte_array[] = new byte[ length];
		Arrays.fill( byte_array, paddingByte);

		switch( alignment) {

			case ALIGN_LEFT:
				System.arraycopy( text.getBytes( characterSetName), 0, byte_array, 0, text.length());
				break;

			case ALIGN_RIGHT:
				int t_offset = length - text.length();
				System.arraycopy( text.getBytes( characterSetName), 0, byte_array, t_offset, text.length());
				break;
			}	

		return byte_array;
	}

	public static byte[] doubleFormating( Double doubleNum, String characterSetName, int fieldLength, int sizeDecimalPart) throws java.io.UnsupportedEncodingException{

		int sizeWholePart = fieldLength - (sizeDecimalPart>0?( sizeDecimalPart + 1):0);

		StringBuffer format = new StringBuffer( fieldLength);

		for( int i=0; i<sizeWholePart; i++) {

			format.append( "#");
		}

		if( sizeDecimalPart > 0) {

			format.append( ".");

			for( int i=0; i<sizeDecimalPart; i++) {

				format.append( "0");
			}
		}	

		DecimalFormat df = new DecimalFormat( format.toString());
		
		return textPadding( df.format( doubleNum.doubleValue()).toString(), characterSetName, fieldLength, ALIGN_RIGHT);
	}

	public static boolean contains( byte[] arr, byte value) {

		boolean found = false;
		for( int i=0; i<arr.length; i++) {

			if( arr[i] == value) {

				found = true;
				break;
			}
		}

		return found;
	}
}