symbol.c

编译原理词法分析源代码（dev c++）

#include "basedata.h"
#include "symbol.h"
#include <conio.h>
#include <string.h>
#include <ctype.h>

char *WORD[WORDLEN]={"BEGIN","CALL","CONST","DO",
			 "END","IF","ODD","PROCEDURE",
			 "READ","THEN","VAR","WHILE",
			 "WRITE"
			 };//保留字字符串表,用于将保留字种别码转为字符串输出
SYMBOL WSYM[WORDLEN]={BEGINSYM,CALLSYM,CONSTSYM,
				   DOSYM,ENDSYM,IFSYM,ODDSYM,
				   PROCSYM,READSYM,THENSYM,
				   VARSYM,WHILESYM,WRITESYM};//保留字种别码表
char* SNAME[SYMBOLNUM]=
  {"NOL","IDENT","NUMBER","PLUS","MINUS","TIMES",
   "SLASH","ODDSYM","EQL","NEQ","LSS","LEQ","GTR",
   "GEQ","LPAREN","RPAREN","COMMA","SEMICOLON",
   "PERIOD","BECOMES","BEGINSYM","ENDSYM","IFSYM",
   "THENSYM","WHILESYM","WRITESYM","READSYM",
   "DOSYM","CALLSYM","CONSTSYM","VARSYM","PROCSYM"};
//单词字符串表,用于将保留字种别码转为字符串输出





SYMBOL sym;//最近已识的单词种别码
char   token[MAXIDLEN+1];//最近已识别的单词
int num;//最近已识别的数字值
char ch;//最近已识别的字符

int col=1,row=1;//当前行和列值
FILE *fd;//指向待编译文件
extern FILE *fout;//指向存放结果文件

void Getchar(void)
{

  ch=fgetc(fd);
  if(ch!=EOF && ch!='\n')
	 col++;
  return;
}

void Getbc(void)
{
  while(ch==SPACE ||ch==TABLE ||ch=='\n')
	{
	  if(ch=='\n') {row++;col=1;}
	  Getchar();
	}//为空字符则一直读至不为空字符
}


void Retract(void)
{
  fseek(fd,-1l,SEEK_CUR);
  col--;
}

void Concat(void)
{
  char temp[2];
  temp[0]=ch;temp[1]='\0';
  strcat(token,temp);
}

int Reserve(void)
{
  int i,j;
  char temp[60];
  j=strlen(token);
  for(i=0;i<j;i++)
   {
	temp[i]=toupper(token[i]);//将当前token字以大写形式存入temp中
   }
  temp[i]='\0';

 for(i=0;i<WORDLEN;i++)
	{

	   if(!strcmp(WORD[i],temp))
		 break;
	}//判断当前token是否是保留字
 if(i>=WORDLEN) i=-1;
 return i;
}

void Errorsym(void)
{
  fprintf(fout,
	"There is error @row: %5d, @col: %5d",
	row,col);
}




int Getsym(void)
{
  int k;
  int flag=TRUE;
  Getchar();
  Getbc();//滤掉白字符
  strcpy(token,"");
  if(isalpha(ch))
	{
	  //以字母开头则是标识符
	  num=0;
	  Concat();
	  Getchar();
	  while(isalnum(ch))
		{
		 Concat();
		 Getchar();
		}
	  Retract();//由于超前搜索了，所以回退一个字符
	  k=Reserve();//判断此标识符是否是保留字
	  if(k!=-1)
		{
		  sym=WSYM[k];//将保留字种别码存入sym中
		}
	  else
		{
		  sym=IDENT;//将一般标识符种别码存入sym中
		}//end else k!=-1;

	}//end of if isalpha
  else if(isdigit(ch))
   {
    //以数字开头则为无符号整数
	Concat();
	Getchar();
	while(isdigit(ch))
		{
		 Concat();
		 Getchar();
		}
	if(isalpha(ch))
	 {
	   flag=FALSE;
		while(isalnum(ch))
		{
		 Concat();
		 Getchar();
		}
	 }//end of flag=FALSE
   Retract();//回退
   if(flag)//若是无符号整数，则将整数值存于num中
	  {sym=NUMBER;num=atoi(token);}
   }//end of if isdigit
  else
   {
	 num=0;
	 switch (ch)
	 {
	 case '+':Concat();sym=PLUS;break;
	 case '-':Concat();sym=MINUS;break;
	 case '*':Concat();sym=TIMES;break;
	 case '/':Concat();sym=SLASH;break;
	 case '(':Concat();sym=LPAREN;break;
	 case ')':Concat();sym=RPAREN;break;
	 case '=':Concat();sym=EQL;break;
	 case '#':Concat();sym=NEQ;break;
/*
   ODDSYM,EQL,NEQ,LSS,LEQ,GTR,GEQ,LPAREN,
   RPAREN,COMMA,SEMICOLON,PERIOD,BECOMES,
*/

	 case ',':Concat();sym=COMMA;break;
	 case '.':Concat();sym=PERIOD;break;
	 case ';':Concat();sym=SEMICOLON;break;
	 case '>':
			  Concat();Getchar();
			  if(ch!='=')//若后不跟'=',则回退
				{sym=GTR;Retract();}
			  else
				{Concat();sym=GEQ;}
			  break;
	 case '<':Concat();Getchar();
			  if(ch!='=')
				{sym=LSS;Retract();}
			  else
				{Concat();sym=LEQ;}
			  break;
	 case ':':Concat();Getchar();
			  if(ch!='=')
				{flag=FALSE;Retract();}
			  else
				{Concat();sym=BECOMES;}
			  break;

	 default :Concat();flag=FALSE;break;

   }//end of switch else char
  }//end of else char
  return flag;
}