lzw.rar_Java实现Lzw_LZW Compression_lzw

package com.anywhere; import java.io.*; /** 一个lzw 压缩算法的 编码 和译码 的实现程序 * 压缩一个已有文件（sourcefile）到目标文件（targetfile） ，然后读取压缩的码； * 此程序采用12位压缩码，词典作多可以存储2^12个词条； * 生成的压缩码 经过解压缩，可以恢复为原先文件； *对文本文件的压缩率，大约为60%,尚不能支持中文的文件输入：） * @author Lai Yongxuan 2003.3.12 * @version 1.0 */ public class lzwCode { /** @see Dictionary */ Dictionary dic=new Dictionary(); /**count1: the bytes of input file,count2:the bytes of output file */ int count1=0,count2=0; /** the max number of the dictionary; *this number can be add to the codebuf[] if * the file has only odd words to be treated ; */ /** the input file : character file or coding file */ BufferedInputStream in; /** the output file: character file or coding file */ BufferedOutputStream out; final short END=4095; /**the entry of the class,and check the arguments first @param args array of string arguments -c sourceFile [targetFile] 建立一个压缩文件 -d sourceFile [targetFile] 解压缩一个文件 @return No return value @exception No ecceptions thrown */ public static void main(String []args) { if ( args.length<=1 || args.length>4 ) { System.out.println("-c sourceFile [targetFile] [-dic] 建立一个压 缩文件\n"); System.out.println("-d sourceFile [targetFile] [-dic] 解压缩一个 文件\n"); } else if(! ( args[0].equals(new String("-c") )||args[0].equals(new String("-d") ) ) ) { System.out.println("-c sourceFile [targetFile] 建立一个压缩文件\ n"); System.out.println("-d sourceFile [targetFile] 解压缩一个文件\n" ); } else if(args.length>=2) { lzwCode a=new lzwCode(args); a.run(args); } return ; } /** the constuctor of the class of "lzwCode " *@param args array of string arguments input at the main() * * */ public lzwCode(String []args) { try{ String f=new String(); in =new BufferedInputStream( new FileInputStream( new File(args[1]))); if(args.length==3 && !args[2].equals(new String("-dic"))) { f=args[2]; } else { int i=args[1].lastIndexOf(new String(".") ); f=args[1].substring(0,i)+((args[0].equals("-c") )?".lzw":".dlzw"); } out=new BufferedOutputStream( new FileOutputStream( new File(f))); }//try catch(FileNotFoundException e ) { System.err.println(e); return; } catch(IOException e ) { System.err.println(e); return; } } /** the entry of the process; @param Srring args[]: array of string arguments input at the main() BufferedInputStream in: the input charstream file BufferedOutputStream out:the output code stream file * @return No return value */ public void run(String args[] ) { if(args[0].equals(new String("-c")) ) { code(in,out); } else { decode(in,out); } if(args[args.length-1].equals(new String("-dic") )) System.out.println(dic.toString ()); } /** input the charstream from a file,and output the code stream to anpther file * @param BufferedInputStream in: the input charstream file BufferedOutputStream out:the output code stream file * @return No return value * */ public void code(BufferedInputStream in,BufferedOutputStream out) { System.out.println("coding...\n"+ ".......\n"); //a:the buffer byte read from the input file,then to be converted to String //buf: the codestream to store in the code file //prefix :the pre_String of the dictory // the indexbuf[] is the index of dictionary to be converted in // the code file //str: the current charecter of the character input Stream byte a[]=new byte[1],buf[]=new byte[3]; String prefix="",cur=""; byte i=0; short indexbuf[]=new short[2]; String str=null; try{ short m=0; while( (a[0]=(byte)in.read() ) != -1 ) { cur=new String(a);// be converted count1++; // the number of bytes of input file str=prefix; str=str.concat(cur); m=(short)dic.indexOf(str); if( m!=-1)//the prefix is in the dictionary, { prefix=str; } else// { if(i==0)//the first indexbuf,store in codebuf[] { indexbuf[0]=(short)dic.indexOf(prefix); i=1; } else// now have 2 index number,then ouput to the code file { indexbuf[1]=(short)dic.indexOf(prefix); zipOutput(out,indexbuf); count2+=3;//3 bytes stored to the code file i=0; } dic.add(str); prefix=cur; }//else }//while // System.out.println("i="+i); if(i==(byte)1) //this is the case that the //input file has only odd index number to store { indexbuf[1]=END;//put a special index number //(the max number of the dictionary) END to the code file zipOutput(out,indexbuf); count2+=3; } dic.add(str); in.close (); out.close (); System.out.println("zip rate:"+(float)count2*100/count1+"% "); }catch(IOException e ) { System.err.println(e); return; } catch(OutDictionaryException e) { System.err.println(e); return; } } /** input the code stream from a file,and output the char stream to anpther file * @param BufferedInputStream in: the input code file BufferedOutputStream out:the output charstream stream file * @return No return value * @exception No return Exception * * */ public void decode(BufferedInputStream in,BufferedOutputStream out) { System.out.println("decoding...\n"+".......\n"); short precode=0,curcode=0; String prefix=null; short i=0; short bufcode[]=new short[2];//2 code read from the code file boolean more=true;//indicate the end of the file or some error while input the file // DataOutputStream out2=new DataOutputStream(out); try{ more=zipInput(in,bufcode);//first input 2 code if(more) { curcode=bufcode[0]; // out2.writeChars(dic.getString(curcode)); stringOut(out,dic.getString(curcode) ); } else System.out.println("error in the beginning..."); while(more) { precode=curcode; if(i==0) { curcode=bufcode[1]; i=1; } else { more=zipInput(in,bufcode); curcode=bufcode[0]; if(bufcode[1]==END) { stringOut(out,dic.getString (bufcode[0] )); break; } i=0; }