ascii_7coding.java

JAVA邮件系统

import java.lang.Integer;

public class Ascii_7Coding  implements Encodeing
{
	private	 byte CodeToNum16(byte code){
		switch( code ){
			case (byte)'0':
			return 0;
			case (byte)'1':
			return 1;
			case (byte)'2':
			return 2;
			case (byte)'3':
			return 3;
			case (byte)'4':
			return 4;
			case (byte)'5':
			return 5;
			case (byte)'6':
			return 6;
			case (byte)'7':
			return 7;
			case (byte)'8':
			return 8;
			case (byte)'9':
			return 9;
			case (byte)'A':
			case (byte)'a':
			return 10;
			case (byte)'B':
			case (byte)'b':
			return 11;
			case (byte)'C':
			case (byte)'c':
			return 12;
			case (byte)'D':
			case (byte)'d':
			return 13;
			case (byte)'E':
			case (byte)'e':
			return 14;
			case (byte)'F':
			case (byte)'f':
			return 15;
		}
		return 0;
	};
	
	//sometime , before encode , we need calc the number of 
	//hight ascii code in buffer;
	public  int  CalcEncodeLengthForCharBuffer( byte[] sSrc ){
		if( sSrc == null )
			return 1;
		int nLength = sSrc.length;
		return CalcEncodeLength( sSrc , nLength );		
	};
	public  int  CalcEncodeLength( byte[] sSrc , int nLength ){
		if( sSrc==null )
			return 1;
		int nCount  = 0;
		for(int i=0;i<nLength;i++ ){
			if( ( ( sSrc[i] & 0x80 ) != 0 )
				|| 
				( sSrc[i] == '=' )
				||
				( sSrc[i] < 0x20 ) 
			  )
				nCount ++;
		}
		return nLength + nCount*2 + 1 + ( nLength / lineCode + 1 ) * 2 ;	
	};
	
	//the buffer should be alloc and free by external module;
	//Now ,it always return true;
	public  int Encode( byte[] sSrc,byte[] sDes,int nSrcLength, 
						int nOffsetSrc ,int nOffsetDes){
		if( nSrcLength == 0 || sSrc==null || sDes==null ){
			return 0;
		}
		int nDes=0;
		String sTemp ;
		for( int i=0 ; i<nSrcLength ; i++){
			if( (  ( sSrc[nOffsetSrc+i]  & 0x80 )!=0 )
				|| ( sSrc[nOffsetSrc+i] == '=' )
				|| ( sSrc[nOffsetSrc+i] < 0x20 ) 
			  ){
				sDes[nOffsetDes+nDes]=(byte)'='; 
				if( ( sSrc[nOffsetSrc+i] & 0xf0 ) != 0 ){
					sDes[nOffsetDes+nDes+1]=(byte)( Integer.toHexString( (int)sSrc[nOffsetSrc+i] ) ).charAt(6); 
					sDes[nOffsetDes+nDes+2]=(byte)( Integer.toHexString( (int)sSrc[nOffsetSrc+i] ) ).charAt(7); 
				}
				else{
					sDes[nOffsetDes+nDes+1]=(byte)'0'; 
					sDes[nOffsetDes+nDes+2]=(byte)( Integer.toHexString( (int)sSrc[nOffsetSrc+i] ) ).charAt(7); 
				}
				nDes += 3;
			}
			else{
				sDes[nOffsetDes+nDes]=sSrc[nOffsetSrc+i]; 
				nDes ++ ;
			}
		}
		return nDes;
	};

	//the buffer should be alloc and free by external module;
	//Now ,it always return true;
	public  int Decode( byte[] sSrc,byte[] sDes,int nSrcLength 
						,int nOffsetSrc ,int nOffsetDes ){
		int nDes = 0;
		if( nSrcLength == 0 || sSrc==null || sDes==null ){
			return 0;
		}
		for( int i=0;i<nSrcLength;i++ ){
			//skip the '\r' '\n'
			if( sSrc[nOffsetSrc+i] == 0xd || sSrc[nOffsetSrc+i] == 0xa ){
				continue;
			}
			if( sSrc[nOffsetSrc+i] == 0 ){
				return nDes;
			}
			if( sSrc[nOffsetSrc+i] == '=' ){
				sDes[nOffsetDes+nDes] = (byte)( ( CodeToNum16(sSrc[nOffsetSrc+i+1]) )*16 
					+ CodeToNum16(sSrc[nOffsetSrc+i+2]) );
				i+=2;
			}
			else{
				sDes[nOffsetDes+nDes]=(byte)((sSrc[nOffsetSrc+i])&0x7f);
			}
			nDes++;
		}
		
		return nDes;
	};
};