课堂的一个LZW程序

这学期上多媒体，写了个LZW的作业。 自己的用过的东西总是丢三落四的，现在粘上来以防下次找不到。

 

 

 

 

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#include <string>#include <iostream>//#include <ext/hash_map>#include <fstream>#include <map>//#include <sstream>#include <cstring>#define DIC_SIZE 2147483640 // pretty big dictionary//the dynamic dictionary index is from 256 to DIC_SIZEusing namespace std;/******************************************************************************/void compress(ifstream &inf, ofstream &outf); // encoding is correctvoid decompress(ifstream &deinf, ofstream &deoutf); //decoding is correct/******************************************************************************/int main(){ while (1) { cout<<"Choose to compress or decompress: /n1: compress 2: decompress 3: quit/n"; int i; cin>>i; if (i == 1) //compression mode { cout<<"please input the to be compressed file name/n/n"; char finname[20]; cin >> finname; ifstream fin(finname, ios::in | ios:: binary); if (!fin.is_open()) { cout<<"/n/nunable to open the file,quit /n"; return 1; } char outname[40]; strcpy(outname, finname); //cout<<outname; strcat(outname, ".compressed"); ofstream fout; fout.open(outname, ios::out | ios:: binary); cout<<"the output name after compression is: "<<outname<<endl; compress(fin, fout); fin.close(); fout.close(); cout<<"finished compression../n/n/n"; } else if (i == 2) //decompression mode { cout<<"please input the to be decompressed file name/n/n"; char decfinname[20]; cin>> decfinname; ifstream decfin(decfinname, ios::in | ios:: binary); if (!decfin.is_open()) { cout<<"/n/nunable to open the file,quit/n"; return 1; } //decfinname = decfinname - ".compressed"; string str1,str2,str3; string decoutname; // name back for decompression int flag = 0; int q; for(q=0; q<20;q++) { if(decfinname[q]=='.') { flag++; } if(flag==2) { break; } } string backname(decfinname, 0, q); ofstream decfout; cout<< "the output name after decompression is : "<<backname.c_str()<<endl; decfout.open(backname.c_str(), ios::out | ios:: binary); decompress(decfin, decfout); cout<<"/nfinished decompression../n/n/n"; } else if (i == 3) //quit mode { cout<<"quiting..../n"; break; } else { cout<<"wrong command.../n"; } } return 0;}/******************************************************************************/void compress(ifstream &inf, ofstream &outf){ cout<<"/n you have chosen the compress mode, please wait while it is being processed...../n"; //build a dictoinary map<string, int > dic; //the firt few words of the dic string stemp; string prestemp;//previous string char *nextfirst = new char[1]; int index = 256; // 0 to 255 have already been occupied by the full ASCII table //build the dictionary using the the full ASCII table so that all the chars will be presented for (int i=0; i<256; i++) { char * temp = new char[2]; temp[0] = (char)i; temp[1] = '/0'; dic[temp] = i; } inf.read(nextfirst,sizeof(char)); while (!inf.eof()) { //reset the stemp to be the first char of ctemp stemp = nextfirst; prestemp = stemp; //if a word is found, continue searching the longest match until no word is found while (dic.find(stemp) != dic.end()) { inf.read(nextfirst, sizeof(char)); prestemp = stemp; // concatnate the word stemp += nextfirst; } map<string ,int>::iterator iter; if ((iter = dic.find(prestemp)) != dic.end()) { int x = iter->second; outf.write((char*)&x, sizeof(x)); } // update the dictionary if (index <= DIC_SIZE)// if not reach the dictionary size yet { dic[stemp] = index++; } //else if reach the dictionary size //the dictionary will be reset from the beginning else { index = 256; dic[stemp] = index++; } }}/******************************************************************************/void decompress(ifstream &fin, ofstream &fout){ map<int ,string> dic; map<int ,string>::iterator iter; string prestr, thisstr, dicstr,outstr; int index,updateindex,temp,lastindex; //init a dictionary for (int i=0; i<256;i++) { char *temps = new char[2]; temps[0] = (char)i; temps[1] = '/0'; dic[i] = temps; } //0 to 255 are the ASCII static dictionary updateindex = 256; fin.read((char*)&index, sizeof(index)); while (!fin.eof()) { lastindex = index; fin.read((char*)&index, sizeof(index)); if ((iter = dic.find(lastindex))!=dic.end()) { thisstr = iter->second; } prestr = thisstr; int size = thisstr.size(); char x[size] ; for(int i=0; i< size ;i++) {x[i] = thisstr[i]; } //put it into the file fout.write(x, sizeof(x)); if ((iter = dic.find(index))!=dic.end()) { thisstr = iter->second; } dicstr = prestr + thisstr[0]; dic[updateindex]= dicstr; if(updateindex <= DIC_SIZE) { updateindex++; } else { updateindex = 256; dic[updateindex]= thisstr; } }}