2.cpp

分析关键字

#include <stdio.h>
#include <string.h>
#include <process.h>
#define MAX 50
void main()
{
FILE *in,*out;/*存放输入字符串和输出单词串的文件*/
char arr[MAX];/*arr数组存放单词符号*/
char currentchar;/*currentchar存放当前输入字符*/
int i=0;/*arr数组的一个指针*/
/*以读方式打开输入文件*/
if((in=fopen("infile.txt","r"))==NULL)
{
 printf("can not open file\n");
 exit(0);
}
/*以写方式打开输出文件*/
if((out=fopen("outfile.txt","w"))==NULL)
{
 printf("cannout open outfile\n");
    exit(1);
}
//去掉开头空格
currentchar=fgetc(in);
while(currentchar==' ')
{ 
 currentchar=fgetc(in);
}
int ch;
while(currentchar!='@')//判断结束符@
{
    while(currentchar==' ')
	{ 
     currentchar=fgetc(in);
	}
/*常数部分判断*/
if((currentchar>='a'&&currentchar<='z')||(currentchar>='A'&&currentchar<='Z')||(currentchar>='0'&&currentchar<='9')||currentchar=='"'||currentchar==' '||currentchar=='('||currentchar==')'||currentchar=='{'||currentchar=='}'||currentchar=='>'||currentchar=='<'||currentchar==','||currentchar==';'||currentchar==':'||currentchar=='+'||currentchar=='-'||currentchar=='*'||currentchar=='/'||currentchar=='='||currentchar=='!'||currentchar=='&'||(ch=currentchar)=='\n'||currentchar==' '||currentchar=='['||currentchar==']'||currentchar=='#')
{
  i=0;//清空arr字符数组
  if(currentchar>='0'&&currentchar<='9')
  {
    arr[i++]=currentchar;
    currentchar=fgetc(in);//再读入下一个字符
      while(currentchar>='0'&&currentchar<='9')
	 {
        arr[i++]=currentchar;
        currentchar=fgetc(in);
	 }
    if(currentchar!='.')//如果当前读入的符号不为小数点，则常数读完毕，输出此常数
	{
     arr[i++]='\0';
     fprintf(out,"%s%d,%c%s%c%s","(",0,'"',arr,'"',")");//格式化输出到目标文件，0代表种别码， arr为内码值，规定用数字本身代表
	}
    else//当前字符为小数点则继续向下读入
	{
    arr[i++]=currentchar;
    currentchar=fgetc(in);
    while(currentchar>='0'&&currentchar<='9')
	{
    arr[i++]=currentchar;
    currentchar=fgetc(in);
	}
    arr[i++]='\0';
    fprintf(out,"%s%d,%c%s%c%s","(",0,'"',arr,'"',")");
	}
  }
/*判断标识符和关键字部分*/
if((currentchar>='a'&&currentchar<='z')||(currentchar>='A'&&currentchar<='Z'))
{
     i=0;//清空arr字符数组
while((currentchar>='a'&&currentchar<='z')||(currentchar>='0'&&currentchar<='9')||(currentchar>='A'&&currentchar<='Z'))
	{
      arr[i++]=currentchar;
      currentchar=fgetc(in);
	}
//把字符数组arr和关键字表比较，判断单词串是关键字还是标识符
    arr[i++]='\0';
    if(strcmp(arr,"if")==0)          fprintf(out,"%s%d,%c%s%c%s","(",1,'"',arr,'"',")");
    else if(strcmp(arr,"else")==0)   fprintf(out,"%s%d,%c%s%c%s","(",2,'"',arr,'"',")");
    else if(strcmp(arr,"while")==0)  fprintf(out,"%s%d,%c%s%c%s","(",3,'"',arr,'"',")");
    else if(strcmp(arr,"do")==0)     fprintf(out,"%s%d,%c%s%c%s","(",4,'"',arr,'"',")"); 
	else if(strcmp(arr,"for")==0)    fprintf(out,"%s%d,%c%s%c%s","(",5,'"',arr,'"',")"); 
	else if(strcmp(arr,"switch")==0)   fprintf(out,"%s%d,%c%s%c%s","(",6,'"',arr,'"',")");
	else if(strcmp(arr,"case")==0)  fprintf(out,"%s%d,%c%s%c%s","(",7,'"',arr,'"',")");
	else if(strcmp(arr,"continue")==0)  fprintf(out,"%s%d,%c%s%c%s","(",8,'"',arr,'"',")");
	else if(strcmp(arr,"break")==0) fprintf(out,"%s%d,%c%s%c%s","(",9,'"',arr,'"',")");
	else if(strcmp(arr,"return")==0)  fprintf(out,"%s%d,%c%s%c%s","(",10,'"',arr,'"',")");
    else if(strcmp(arr,"goto")==0)  fprintf(out,"%s%d,%c%s%c%s","(",11,'"',arr,'"',")");
	else if(strcmp(arr,"auto")==0)  fprintf(out,"%s%d,%c%s%c%s","(",12,'"',arr,'"',")");
	else if(strcmp(arr,"defalut")==0)  fprintf(out,"%s%d,%c%s%c%s","(",13,'"',arr,'"',")");
	else if(strcmp(arr,"void")==0)  fprintf(out,"%s%d,%c%s%c%s","(",14,'"',arr,'"',")");
	else if(strcmp(arr,"const")==0)  fprintf(out,"%s%d,%c%s%c%s","(",15,'"',arr,'"',")");
	else if(strcmp(arr,"enum")==0)  fprintf(out,"%s%d,%c%s%c%s","(",16,'"',arr,'"',")");
	else if(strcmp(arr,"typedef")==0)  fprintf(out,"%s%d,%c%s%c%s","(",17,'"',arr,'"',")");
    else if(strcmp(arr,"static")==0)  fprintf(out,"%s%d,%c%s%c%s","(",18,'"',arr,'"',")");
	else if(strcmp(arr,"sizeof")==0)  fprintf(out,"%s%d,%c%s%c%s","(",19,'"',arr,'"',")");
	else if(strcmp(arr,"int")==0)  fprintf(out,"%s%d,%c%s%c%s","(",20,'"',arr,'"',")");
	else if(strcmp(arr,"long")==0)  fprintf(out,"%s%d,%c%s%c%s","(",21,'"',arr,'"',")");
	else if(strcmp(arr,"char")==0)  fprintf(out,"%s%d,%c%s%c%s","(",22,'"',arr,'"',")");
	else if(strcmp(arr,"float")==0)  fprintf(out,"%s%d,%c%s%c%s","(",23,'"',arr,'"',")");
	else if(strcmp(arr,"double")==0)  fprintf(out,"%s%d,%c%s%c%s","(",24,'"',arr,'"',")");
	else if(strcmp(arr,"short")==0)  fprintf(out,"%s%d,%c%s%c%s","(",25,'"',arr,'"',")");
	else if(strcmp(arr,"signed")==0)  fprintf(out,"%s%d,%c%s%c%s","(",26,'"',arr,'"',")");
	else if(strcmp(arr,"unsigned")==0)  fprintf(out,"%s%d,%c%s%c%s","(",27,'"',arr,'"',")");
	else if(strcmp(arr,"struct")==0)  fprintf(out,"%s%d,%c%s%c%s","(",28,'"',arr,'"',")");
	else if(strcmp(arr,"register")==0)  fprintf(out,"%s%d,%c%s%c%s","(",29,'"',arr,'"',")");
	else if(strcmp(arr,"extern")==0)  fprintf(out,"%s%d,%c%s%c%s","(",30,'"',arr,'"',")");
	else if(strcmp(arr,"volatile")==0)  fprintf(out,"%s%d,%c%s%c%s","(",31,'"',arr,'"',")");
    else if(strcmp(arr,"union")==0)  fprintf(out,"%s%d,%c%s%c%s","(",32,'"',arr,'"',")");
	else    fprintf(out,"%s%d,%c%s%c%s","(",33,'"',arr,'"',")");
}
//判断运算符和界符
switch(currentchar)
{
case'+':fprintf(out,"%s%d,%c%c%c%s","(",41,'"',currentchar,'"',")");currentchar=fgetc(in);break;
case'-':fprintf(out,"%s%d,%c%c%c%s","(",42,'"',currentchar,'"',")");currentchar=fgetc(in);break;
case'*':fprintf(out,"%s%d,%c%c%c%s","(",43,'"',currentchar,'"',")");currentchar=fgetc(in);break;
case'/':fprintf(out,"%s%d,%c%c%c%s","(",44,'"',currentchar,'"',")");currentchar=fgetc(in);break;
case'%':fprintf(out,"%s%d,%c%c%c%s","(",45,'"',currentchar,'"',")");currentchar=fgetc(in);break;
case'~':fprintf(out,"%s%d,%c%c%c%s","(",46,'"',currentchar,'"',")");currentchar=fgetc(in);break;
case'^':fprintf(out,"%s%d,%c%c%c%s","(",47,'"',currentchar,'"',")");currentchar=fgetc(in);break;
case'|':fprintf(out,"%s%d,%c%c%c%s","(",48,'"',currentchar,'"',")");currentchar=fgetc(in);break;
case'?':fprintf(out,"%s%d,%c%c%c%s","(",49,'"',currentchar,'"',")");currentchar=fgetc(in);break;
case'=':fprintf(out,"%s%d,%c%c%c%s","(",50,'"',currentchar,'"',")");currentchar=fgetc(in);break;
case'>':fprintf(out,"%s%d,%c%c%c%s","(",51,'"',currentchar,'"',")");currentchar=fgetc(in);break;
case'<':fprintf(out,"%s%d,%c%c%c%s","(",52,'"',currentchar,'"',")");currentchar=fgetc(in);break;
case'!':fprintf(out,"%s%d,%c%c%c%s","(",53,'"',currentchar,'"',")");currentchar=fgetc(in);break;
case'&':fprintf(out,"%s%d,%c%c%c%s","(",54,'"',currentchar,'"',")");currentchar=fgetc(in);break;
case':':fprintf(out,"%s%d,%c%c%c%s","(",55,'"',currentchar,'"',")");currentchar=fgetc(in);break;
case'"':fprintf(out,"%s%d,%c%c%c%s","(",56,'"',currentchar,'"',")");currentchar=fgetc(in);break;
case'#':fprintf(out,"%s%d,%c%c%c%s","(",57,'"',currentchar,'"',")");currentchar=fgetc(in);break;
case'.':fprintf(out,"%s%d,%c%c%c%s","(",58,'"',currentchar,'"',")");currentchar=fgetc(in);break;
case',':fprintf(out,"%s%d,%c%c%c%s","(",59,'"',currentchar,'"',")");currentchar=fgetc(in);break;
case';':fprintf(out,"%s%d,%c%c%c%s","(",60,'"',currentchar,'"',")");currentchar=fgetc(in);break;
case'{':fprintf(out,"%s%d,%c%c%c%s","(",61,'"',currentchar,'"',")");currentchar=fgetc(in);break;
case'}':fprintf(out,"%s%d,%c%c%c%s","(",62,'"',currentchar,'"',")");currentchar=fgetc(in);break;
case'[':fprintf(out,"%s%d,%c%c%c%s","(",63,'"',currentchar,'"',")");currentchar=fgetc(in);break;
case']':fprintf(out,"%s%d,%c%c%c%s","(",64,'"',currentchar,'"',")");currentchar=fgetc(in);break;
case'(':fprintf(out,"%s%d,%c%c%c%s","(",65,'"',currentchar,'"',")");currentchar=fgetc(in);break;
case')':fprintf(out,"%s%d,%c%c%c%s","(",66,'"',currentchar,'"',")");currentchar=fgetc(in);break;
}

while((ch=currentchar)=='\n')
{
	currentchar=fgetc(in);
}
}
else//未能识别部分的出错处理
{
    fprintf(out,"%s,%c%c%c","error",'"',currentchar,'"');
    currentchar=fgetc(in);
}
}//结束开头while语句
/*关闭文件退出*/
fclose(in);
fclose(out);
}