编译器预处理实现

我们写代码一般都会写一些注释，为了让人更好的理解代码，但是对于编译器来说，这些注释都需要去除，为了实现预处理，就是去除注释、换行、回车等，我用DFA（确定有限自动机）来实现。

#include <iostream>#include  <fstream>using  namespace std;#define R 10#define C 8//DFAint DFA[R][C]= \{      /* /   *  \   '   " \n other *//*0*/{0, 1, 0, 0, 8, 6, 0, 0},/*1*/{0, 2, 3, 0, 8, 0, 0, 0},/*2*/{0, 2, 2, 4, 2, 2, 0, 2},/*3*/{0, 3, 5, 3, 3, 3, 3, 3},/*4*/{0, 2, 2, 4, 2, 2, 4, 2},/*5*/{0, 0, 5, 3, 3, 3, 3, 3},/*6*/{0, 6, 6, 7, 6, 0, 6, 6},/*7*/{0, 6, 6, 7, 6, 6, 6, 6},/*8*/{0, 8, 8, 9, 0, 8, 8, 8},/*9*/{0, 8, 8, 8, 8, 8, 8, 8}};//字符转码int code(char ch){int chars = 7;switch(ch){case '/': chars=1;break;case '*': chars=2;break;case '\\':chars=3;break;case '\'':chars=4;break;case '\"':chars=5;break;case '\n':chars=6;break;default:chars=7;break;}return chars;}//判断是空格、tab、回车、换行等int Judge(char curch){if((curch == ' '||curch == '\t' || curch=='\r' || curch == '\n' || curch == '\\')) return 1;else return 0;}void  Pretreat(const char*src, const char *des){if(src == NULL || des == NULL) return;int i = 0;int j = 0;        //打开文件ifstream infile(src);if(infile.fail()){cout<<"open  "<<src<< "  fail!"<<endl;return;}ofstream outfile(des, ios::out);if(outfile.fail()){cout<<"open or create "<<des<< "  fail!"<<endl;return;}        //获取文件大小infile.seekg(0,ios::end);     unsigned int size=static_cast<unsigned int>(infile.tellg()); infile.seekg(0,ios::beg);    char *rbuffer = new char [sizeof(char)*size];char *wbuffer = new char [sizeof(char)*size];memset(rbuffer, '\0', size);memset(wbuffer, '\0', size);infile.get(rbuffer, size, infile.eof());         //当前字符char curch=' ';        //前一个字符char prech = ' ';         //前一个状态int prestate = DFA[0][0];        //当前状态int curstate = DFA[0][0];int space = 0;while((curch = rbuffer[i])!='\0'){curstate = DFA[curstate][code(curch)];switch (curstate){case 0:                        //这里需要考虑除号‘/’，比如 12/3，这当然不能去除if(prestate == 1  && code(prech) == 1){wbuffer[j++] = prech;}else if(code(curch) == 1){break;}if(Judge(curch)&& space == 0){//if(curch == '\n')//{//wbuffer[j++] ='\n';//}//else//{    wbuffer[j++] =' ';   //}space = 1;break;}else if(Judge(curch)&& space == 1){break;}else{space = 0;}case 6:case 7:case 8:case 9:wbuffer[j++] = curch;break;}prestate = curstate;prech = curch;i++;}outfile<<wbuffer;delete [] rbuffer;delete [] wbuffer;infile.close();outfile.close();}int main(){char *src = "D:\\project\\deal.cpp";char *des="D:\\result.cpp";Pretreat(src, des);return 0;}