test.cpp

一个用C++编写的C语言词法分析程序

//#include<iostream.h>
#include "iostream.h"
#include"streambuf.h"

#include<ctype.h>
#include<string.h>
#include<stdio.h>
#include<stdlib.h>

#define ID 6   
#define INT 7
#define LT 8
#define LE 9
#define EQ 10
#define NE 11
#define GT 12
#define GE 13
#define FZ 14       
#define DEV 15

 

struct KeyWord        //关键字结构
{
 char *word;
 int id;
};

KeyWord keyword[]={    //关键字数组
 {"begin",1},
 {"end",2},
 {"if",3},
 {"then",4},
 {"else",5},
 {"integer",16},
 {"float",17},
 {"double",18}
};


char TOKEN[20];
int graphnum=1;     //记录错误所在的位置


int lookup(char *string);
void out(int id ,char *string);
void report_error(char ERR_CH);
bool isalpha(char c) ;
bool isdigit(char c);
bool isalnum(char c);
void scanner_example(FILE *fp);

 

int lookup(char *string)
{
 for(int i=0;i<sizeof(keyword)/sizeof(KeyWord);i++)
 {
  if(strcmp(string,keyword[i].word)==0)
   return keyword[i].id;
 }
 return 0;
}

void out(int id ,char *string)
{
 printf("(%d,%s)\n",id,string);;
}

void report_error(char ERR_CH)        //错误处理程序
{
 printf("undeclared identifler %c int %d line!\n",ERR_CH,graphnum);
}

bool isalpha(char c)  
{
 if( (c>='a'&&c<='z') || (c>='A'&&c<='Z') )
  return true;
 else
  return false;
}

bool isdigit(char c)
{
 if(c>='0'&&c<='9')
  return true;
 else
  return false;
}

bool isalnum(char c)
{
 if( isalpha(c) || isdigit(c) )
  return true;
 else
  return false;
}

void scanner_example(FILE *fp)
{
 char ch;
 int i,c;
 
 while(!feof(fp))
 {

 ch=fgetc(fp);
 if(isalpha(ch)) 
 {
  TOKEN[0]=ch;
  ch=fgetc(fp);
  i=1;
  while(isalnum(ch)) 
  {
   TOKEN[i]=ch;
   i++;
   ch=fgetc(fp);
  }
  TOKEN[i]='\0';
  fseek(fp,-1,1);
  c=lookup(TOKEN);
  if(c==0)
   out (ID,TOKEN);
  else
   out (c," ");
 }
 else if(isdigit(ch))
 {
  TOKEN[0]=ch;
  ch=fgetc(fp);
  i=1;
  while(isdigit(ch))
  {
   TOKEN[i]=ch;
   i++;
   ch=fgetc(fp);
  }
  TOKEN[i]='\0';
  fseek(fp,-1,1);
  out(INT,TOKEN);
 }
 else
  switch(ch)
  {
   case '<': ch=fgetc(fp);
      if(ch=='=')
       out(LE," ");
      else if(ch=='>')
       out(NE," ");
      else
      {
       fseek(fp,-1,1);
       out(LT," ");
      }
      break;
   case '=': out(EQ, " "); break;
   case '>': ch=fgetc(fp);
      if(ch=='=')
       out(GE," ");
      else
      {
       fseek(fp,-1,1);
       out(GT," ");
      }
      break;
   case ':': ch=fgetc(fp);
         if(ch=='=')              // := 为赋值语句
       out(FZ," ");
      else
      {
       fseek(fp,-1,1);
       report_error(ch);
      }
      break;
   case '/': ch=fgetc(fp);   //删除程序中的注释
      if(ch=='/')
      {
       do
       {
        ch=fgetc(fp);
       }while(ch!='\n');
       graphnum++;
      }
      else
      {
       fseek(fp,-1,1);
       out(DEV," ");
      }
      break;
   case ' ' : break;                 //删除程序中的空格             
   case '\n': graphnum++; break;   //删除程序中的回车,并记录程序编译到第几行           
   case ' ': break;      //删除程序中的横向制表符
   case -1 : break;      //删除文件尾符号
   default : report_error(ch);
     break;
  }

 }
 return;
}
void main(int argc,char *argv[])
{
 FILE *fp;

 try
 {
  if(argc!=2)
   throw argc;
  fp=fopen(argv[1],"r");
  if(!fp)
   throw argv[1];
  
 }
 
 catch(char *str)
 {
  cout<<"打开文件 : "<<str<<" 时发生错误!"<<endl;
  exit(1);
 }

 catch(int)
 {
  cout<<"请输入一个文件名!"<<endl;
  exit(1);
 }


 scanner_example(fp);

 fclose (fp);
}