scanner.cpp

编译器：用于实现一个简单的编译器的语法分析功能

#include "scanner.h"
#define TOKEN_LEN 100
unsigned int LineNo;

static FILE *InFile;
static char TokenBuffer[TOKEN_LEN];
//===============================================
//========初始化词法分析器=======================
extern int InitScanner(const char *FileName)
{
	LineNo=1;
	InFile=fopen(FileName,"r");
 	if (InFile!=NULL)
		return 1;
	else 
		return 0;
}
//--------------关闭词法分析其器-------------
extern void CloseScanner(void )
{
	if (InFile!=NULL)
		fclose(InFile);
}
//-------从输入源程序中读入一个字符---------
static char GetChar(void)
{
	int Char=getc(InFile);
	return toupper(Char);

}
//--------把预读的字符退回到输入源程序中--------
static void BackChar(char Char)
{
	if (Char!=EOF)
		ungetc(Char,InFile);
}
//-------------假如字符到记号缓冲区中-------------
static void AddCharTokenString (char Char)
{
	int TokenLength=strlen (TokenBuffer);
	if (TokenLength+1>=sizeof(TokenBuffer))
		return;
	TokenBuffer[TokenLength]=Char;
	TokenBuffer[TokenLength+1]='\0';

};
//---------清空记号缓冲区-------------
static void EmptyTokenString()
{
	memset(TokenBuffer,0,TOKEN_LEN);
}
//------------判断所给的字符串是否在符号表中--------------------
static Token JudgeKeyToken(const char *IDString)
{
	int loop;
	for (loop=0;loop<sizeof (TokenTab[0]);loop++)
	{
		if (strcmp(TokenTab[loop].lexeme,IDString)==0)
		return TokenTab[loop];
	}
	Token errortoken;
	memset(&errortoken,0,sizeof(Token));
	errortoken.type=ERRTOKEN;
	return errortoken;
}
//---------------------获取一个记号------------------------
extern Token GetToken(void)
{
	Token token;
	int Char;

	memset(&token,0,sizeof(Token));
	EmptyTokenString();
	token.lexeme=TokenBuffer;
	for(;;)
	{
		Char=GetChar();
		if (Char==EOF)
		{
			token.type=NONTOKEN;
			return token;
		}
		if (Char=='\n')
			LineNo++;
		if (!isspace(Char))
			break;
	}//end of for

	AddCharTokenString(Char);
	if (isalpha(Char))
	{
		for(;;)
		{
			Char=GetChar();
			if (isalnum(Char))
				AddCharTokenString(Char);
			else
				break;
		}
		BackChar(Char);
		token=JudgeKeyToken(TokenBuffer);
		token.lexeme =TokenBuffer;
		return token;

	}
	else if (isdigit(Char))
	{
		for(;;)
		{
			Char=GetChar();
			if(isdigit(Char))
				AddCharTokenString(Char);
			else
				break;

		}
		if(Char=='.')
		{
			AddCharTokenString(Char);
			for(;;)
			{
				Char=GetChar();
				if (isdigit(Char))
					AddCharTokenString(Char);
				else
					break;
			}			
		}
		BackChar(Char);
			token.type=CONST_ID;
			token.value =atof(TokenBuffer);
			return token;
	}
	else
	{
			switch(Char)
			{
			case ';':token.type =SEMICO;
				break;
			case '(':token.type=L_BRACKET;
				break;
			case ')':token.type =R_BRACKET;
				break;
			case ',':token.type =COMMA;
				break;
			case '+':token.type =PLUS;
				break;
			case '-':Char=GetChar();
				if (Char=='-')
				{
					while(Char!='\n'&&Char!=EOF)
						Char=GetChar();
					BackChar(Char);
					return GetToken();
				}
				else
				{
					BackChar(Char);
					token.type =MINUS;
					break;
				}
			case '/': Char=GetChar();
				if (Char=='/')
				{
					while(Char!='\n'&&Char!=EOF)
						Char=GetChar();
					BackChar(Char);
					return GetToken();
				}
				else
				{
					BackChar(Char);
					token.type =DIV;
					break;
				}
			case '*': 
				Char=GetChar();
				if (Char=='*')
				{
					token.type =POWER;
					break;
				}
				else
				{
					BackChar(Char);
					token.type =MUL;
					break;
				}
			default:token.type =ERRTOKEN;
				break;

			}//end of switch
		}//end of else
	
	return token;

}