scan.cpp

一个词法语法分析器

#include "globals.h"                     //分析器的词法扫描部分
#include "scan.h"


void Do_Tag(char * strSource);           //识别标识符的中间状态
void Do_Digit(char * StrSource);         //识别数字中间状态
void Do_EndOfTag(char * strSource);       //识别标识符最后一个状态
void Do_EndOfDigit(char * strSource);     //识别最后一个数字状态
void Do_EndOfEqual(char * strSource);     //=，==
void Do_EndOfPlus(char * strSource);      //+
void Do_EndOfSubtraction(char * strSource);  //-
void Do_EndOfMultiply(char * strSource);     //*
void Do_EndOfDivide(char * strSource);       ///
void Do_EndOfLParen(char * strSource);       //(
void Do_EndOfRParen(char * strSource);       //)
void Do_EndOfLeftBracket1(char * strSource);  //[
void Do_EndOfRightBracket1(char * strSource); //]
void Do_EndOfLeftBracket2(char * strSource);  //{
void Do_EndOfRightBracket2(char * strSource); //}
void Do_EndOfColon(char * strSource);     //:
void Do_EndOfComma(char * strSource);     //,
void Do_EndOfSemicolon(char * strSource); //;
void Do_EndOfMore(char * strSource);      //>,>=
void Do_EndOfLess(char * strSource);      //<,<=
void Do_EndOfEnd(char * strSource);       //用'\0'作为源程序结束
void PrintError(int nColumn, int nRow, char chInput); //词法分析错误输出
void Scaner(void);                       //词法扫描函数
void scaner(void);

extern char * strSource;                 //待分析的源程序
extern FILE * fw;                        //结果输出文件
int gnColumn,
    gnRow,                               //行列号
	gnLocate,                            //下一个字符脚标
	gnLocateStart;                       //下一个单词开始位置

WORD uWord;  //Word uWord;              扫描出的单词

char * KEY_WORDS[20] = {"main","int","char","if","else","for",
                       "while","void","bool","string","this",
					   "double","public","private","new","true",
					   "false","print","null","class"};  //_ _KEY

int IsDigit(char chInput)                //判断是否数字
{
	if (chInput<='9' && chInput>='0')return 1;
	else return 0;
}

int IsChar(char chInput)                //判断是否字母
{
	if ((chInput<='z' && chInput>='a')
		||(chInput<='Z' && chInput>='A'))
		return 1;
	else return 0;
}


void Do_Start(char * strSource)         //开始识别最先一个单词
{
	gnLocateStart = gnLocate;        //gnLocateStart = gnLocate
	switch(strSource[gnLocate]){       //根据第一个字符判断
	case '+':Do_EndOfPlus(strSource);                break;
	case '-':Do_EndOfSubtraction(strSource);         break; 
    case '*':Do_EndOfMultiply(strSource);            break; 
	case '/':Do_EndOfDivide(strSource);              break;  
	case '(':Do_EndOfLParen(strSource);              break; 
    case ')':Do_EndOfRParen(strSource);              break; 
	case '[':Do_EndOfLeftBracket1(strSource);        break; 
	case ']':Do_EndOfRightBracket1(strSource);       break; 
    case '{':Do_EndOfLeftBracket2(strSource);        break; 
	case '}':Do_EndOfRightBracket2(strSource);       break; 
	case ':':Do_EndOfColon(strSource);               break; 
    case ',':Do_EndOfComma(strSource);               break; 
	case ';':Do_EndOfSemicolon(strSource);           break; 
	case '>':Do_EndOfMore(strSource);                break; 
    case '<':Do_EndOfLess(strSource);                break; 
	case '=':Do_EndOfEqual(strSource);               break; 
    case '\0':Do_EndOfEnd(strSource);                break;
	default:
		if(IsChar(strSource[gnLocate]))         //是标识符或关键字
		{     
			Do_Tag(strSource);
		}
		else if(IsDigit(strSource[gnLocate]))  //可能是整数
		{ 
			uWord.value.T2 = strSource[gnLocate] - '0';
			Do_Digit(strSource);
		}
		else                                   //其他符号
		{                                
			if(strSource[gnLocate] != ' '   
				&& strSource[gnLocate] != '\t'
				&& strSource[gnLocate] != '\n'
				&& strSource[gnLocate] != '\r')
			{
				PrintError(gnColumn, gnRow, strSource[gnLocate]);
			}
			if(strSource[gnLocate] == '\n'
				|| strSource[gnLocate] == '\r')
			{
				gnColumn++;
				gnRow = 1;
			}
			else if(strSource[gnLocate] == '\t')
			{
				gnColumn += _TAB_LEGNTH; 
			}
			else gnRow++;

			gnLocate++;

			Do_Start(strSource);  
		}
		break;
	}
	return;
}


void Do_Tag(char * strSource)         //识别标识符的中间状态
{
	gnLocate++;
	gnRow++;
	if(IsChar(strSource[gnLocate]) || IsDigit(strSource[gnLocate])) //是数字或字母
	{ 
		Do_Tag(strSource);
	}
	else Do_EndOfTag(strSource);
	return;
}

void Do_Digit(char * strSource)     //识别整数中间状态
{
	gnLocate++;
	gnRow++;
	if(IsDigit(strSource[gnLocate]))//是数字
	{    
		uWord.value.T2 = uWord.value.T2 * 10  //累加识别数字
			+ strSource[gnLocate] - '0';
		Do_Digit(strSource);
	}
	else Do_EndOfDigit(strSource);
	return;
}

void Do_EndOfTag(char * strSource)        //标识符最后状态
{
	int nLoop;
	uWord.syn=_SYN_ID;                   //单词种别码缺省为标识符
	strncpy(uWord.value.T1, strSource+gnLocateStart, gnLocate-gnLocateStart);//记录标识符
	uWord.value.T1[gnLocate-gnLocateStart] = '\0';
	nLoop = 0;

	while(strcmp(KEY_WORDS[nLoop], "class")) //_KEY_WORD_END)){  //查关键字表，是否关键字
	{ 
		if(! strcmp(KEY_WORDS[nLoop], uWord.value.T1))	//比较和某关键字相符
		{
			uWord.syn = nLoop + 1;      //设置正确的syn          
			break;
		}
		nLoop++;
	}
	return;
}

void Do_EndOfDigit(char * strSource)    //识别数字最后状态
{
	uWord.syn = _SYN_NUM;
	return;
}

void Do_EndOfEqual(char * strSource)    //=，==
{
	if(strSource[gnLocate+1] != '=')
	{
		uWord.syn = _SYN_ASSIGN;
		uWord.value.T3 = strSource[gnLocate];
	}
	else                               //==
	{                             
		gnLocate++;
		gnRow++;
		uWord.syn = _SYN_EQ;
		strcpy(uWord.value.T1, "==");
	}
	gnLocate++;
	gnRow++;
	return;
}

void Do_EndOfPlus(char * strSource)   //+
{
	uWord.syn = _SYN_PLUS;
	uWord.value.T3 = strSource[gnLocate];

	gnLocate++;
	gnRow++;
	return;
}

void Do_EndOfSubtraction(char * strSource)  //-
{
	uWord.syn = _SYN_MINUS;
	uWord.value.T3 = strSource[gnLocate];

	gnLocate++;
	gnRow++;
	return;
}

void Do_EndOfMultiply(char * strSource)   //*
{
	uWord.syn = _SYN_TIMES;
	uWord.value.T3 = strSource[gnLocate];

	gnLocate++;
	gnRow++;
	return;
}

void Do_EndOfDivide(char * strSource)    ///
{
	uWord.syn = _SYN_DIVIDE;
	uWord.value.T3 = strSource[gnLocate];

	gnLocate++;
	gnRow++;
	return;
}

void Do_EndOfLParen(char * strSource)   //（
{
	uWord.syn = _SYN_LPAREN;
	uWord.value.T3 = strSource[gnLocate];

	gnLocate++;
	gnRow++;
	return;
}

void Do_EndOfRParen(char * strSource)   //）
{
	uWord.syn = _SYN_RPAREN;
	uWord.value.T3 = strSource[gnLocate];

	gnLocate++;
	gnRow++;
	return;
}

void Do_EndOfLeftBracket1(char * strSource)    //[
{
	uWord.syn = _SYN_LEFTBRACKET1;
	uWord.value.T3 = strSource[gnLocate];

	gnLocate++;
	gnRow++;
	return;
}

void Do_EndOfRightBracket1(char * strSource)  //]
{
	uWord.syn = _SYN_RIGHTBRACKET1;
	uWord.value.T3 = strSource[gnLocate];

	gnLocate++;
	gnRow++;
	return;
}

void Do_EndOfLeftBracket2(char * strSource)  //{
{
	uWord.syn = _SYN_LEFTBRACKET2;
	uWord.value.T3 = strSource[gnLocate];

	gnLocate++;
	gnRow++;
	return;
}

void Do_EndOfRightBracket2(char * strSource) //}
{
	uWord.syn = _SYN_RIGHTBRACKET2;
	uWord.value.T3 = strSource[gnLocate];

	gnLocate++;
	gnRow++;
	return;
}

void Do_EndOfColon(char * strSource)     //：
{
	uWord.syn = _SYN_COLON;
	uWord.value.T3 = strSource[gnLocate];

	gnLocate++;
	gnRow++;
	return;
}

void Do_EndOfComma(char * strSource)  //，
{
	uWord.syn = _SYN_COMMA;
	uWord.value.T3 = strSource[gnLocate];

	gnLocate++;
	gnRow++;
	return;
}

void Do_EndOfSemicolon(char * strSource)  //；
{
	uWord.syn = _SYN_SEMICOLON;
	uWord.value.T3 = strSource[gnLocate];

	gnLocate++;
	gnRow++;
	return;
}

void Do_EndOfMore(char * strSource)  //>，>=
{
	if(strSource[gnLocate+1] != '=') //>
	{  
		uWord.syn = _SYN_LG;
		uWord.value.T3 = strSource[gnLocate];
	}
	else              //>=
	{          
		gnLocate++;
		gnRow++;
		uWord.syn = _SYN_ME;
		strcpy(uWord.value.T1, ">=");
	}
	gnLocate++;
	gnRow++;
	return;
}

void Do_EndOfLess(char * strSource)  //<,<=
{
	if(strSource[gnLocate+1] != '=') //<
	{ 
		uWord.syn = _SYN_LT;
		uWord.value.T3 = strSource[gnLocate];
	}
	else   //<=
	{ 
		gnLocate++;
		gnRow++;
		uWord.syn = _SYN_LE;
		strcpy(uWord.value.T1, "<=");
	}
	gnLocate++;
	gnRow++;
	return;
}

void Do_EndOfEnd(char * strSource)   //读到'\0',源程序结束
{
	uWord.syn = _SYN_END;
	uWord.value.T3 = strSource[gnLocate];

	gnLocate++;
	gnRow++;
	return;
}

void PrintWord(WORD uWord)   //Word uWord 打印二元组
{
	
	if(uWord.syn <= _SYN_ID    //关键字、标识符有错误
		|| uWord.syn == _SYN_ME  //>=
		|| uWord.syn == _SYN_LE  //<=
		|| uWord.syn == _SYN_EQ)  //==
	{
		fprintf(fw,"\n%s\t               %d", uWord.value.T1, uWord.syn);
	}
	else if(uWord.syn == _SYN_NUM)  //数字
	{
		fprintf(fw,"\n%d\t               %d", uWord.value.T2, uWord.syn);
	} 
	else               //其他符号
	{
		fprintf(fw,"\n%c\t               %d", uWord.value.T3, uWord.syn);
	}
	return;
}

void ApartWord(char * strSource)  //根据输入的源程序识别所有的单词
{
	gnColumn = gnRow = 1;
	gnLocate = gnLocateStart = 0;
	fprintf(fw,"\n词法分析结果:");
	fprintf(fw,"\n单词符号             种别码"); 
	                        
	while(strSource[gnLocate])
	{
		Scaner();
	}
	return;
}

void Scaner(void)           //词法扫描函数
{
	Do_Start(strSource);    //识别出一个单词	
	PrintWord(uWord);       //打印二元组
	return;
}

void scaner(void)
{
	Do_Start(strSource);    //识别出一个单词	
//	return;
}

void PrintError(int nColumn, int nRow, char chInput)
//打印词法扫描发现的错误
{
	fprintf(fw,"\nCol:%d  Row:%d :%c", nColumn, nRow, chInput);
	fprintf(fw,"(无法识别的单词)");
	return;
}