lex.cpp

编译器

#include "stdafx.h"
#include "Lex.h"
#include "string.h"
#include "Type.h"
#include "Token.h"
#include <ctype.h>

Lex::Lex(char *p)
{
	this->sql=new char[strlen(p)+1];
	strcpy(this->sql,p);
	ptr=0;
	end=strlen(this->sql);
	token=new Token();
}

bool Lex::hasNext()
{
	return(ptr<(end-1));
}
void Lex::back()
{
	ptr=backp;
}
Token* Lex::getNextToken()
{
	Type type1;
	if(ptr>=end)
		return NULL;
	backp=ptr;    
	int i=0;
	char temp[20];
	char c;
	c=getAt(this->sql,ptr);
    if(c=='*')
	{
		temp[i++]=c;
        token->type=type1.STAR;
		ptr++;
		temp[i]='\0';
		if(c=getAt(this->sql,ptr)==' ')ptr++;
	}
	else if(c==',')
	{
		temp[i++]=c;
        token->type=type1.DIVIDE;
		ptr++;
		temp[i]='\0';
		if(c=getAt(this->sql,ptr)==' ')ptr++;
	}
	else if (isCompare(c)) {
			temp[i++]=c;
            token->type=type1.COMPARE;
		     ptr++;
			 temp[i]='\0';
			 if(c=getAt(this->sql,ptr)==' ')ptr++;
		} 
		else if (isBracket(c)) {
			temp[i++]=c;
            token->type=type1.BRACKET;
		    ptr++;
			temp[i]='\0';
			if(c=getAt(this->sql,ptr)==' ')ptr++;
		}
		else {
			if (c == '\'') {
			   c=getAt(this->sql,++ptr);
				while (ptr <= end && c != '\'' && c != ' ') {
					temp[i++]=c;
					c=getAt(this->sql,++ptr);
				}
				if (c == '\'') {
					token->type = type1.VARCHAR;
					ptr++;
				} 			
			}
			else if (isalpha(c)) {
				temp[i++]=c;
				c=getAt(this->sql,++ptr);
				while (ptr <= end && isdigit(c)||isalpha(c)) {
					temp[i++]=c;
				    c=getAt(this->sql,++ptr);
				}
				if(c == '.'){
					temp[i++]=c;
				    c=getAt(this->sql,++ptr);
					if(isalpha(c)){
						while (ptr <= end && (isdigit(c)||isalpha(c))) {
							temp[i++]=c;
				            c=getAt(this->sql,++ptr);
						}
					} 
				}
				if(c=getAt(this->sql,ptr)==' ')ptr++;
                temp[i]='\0';
				char *tmp;
	            tmp=new char[i];
				tmp=&temp[0];
				if (strcmp(tmp,"and")==0 ||strcmp(tmp,"or")==0){
					token->type = type1.LOGIC;
				}
				else if(strcmp(tmp,"select")==0 ||strcmp(tmp,"from")==0 ||strcmp(tmp,"where")==0){

					token->type = type1.KEY;
				}
				else {
					token->type = type1.ATTRI;
				}
			}
			else if (isdigit(c)) {
				    temp[i++]=c;
				    c=getAt(this->sql,++ptr);
				while (isdigit(c)) {
					c=getAt(this->sql,ptr);
					temp[i++]=c;
					c=getAt(this->sql,++ptr);
				}
				if(c == '.'){
					temp[i++]=c;
				    c=getAt(this->sql,++ptr);
					if(isdigit(c)){
						while (isdigit(c)) {
						temp[i++]=c;
				    c=getAt(this->sql,++ptr);
						}
					} 
					token->type = type1.DOUBLE;
				}
				else{
					token->type = type1.INTEGER;
				}
				temp[i]='\0';
		        if(c=getAt(this->sql,ptr)==' ')ptr++;
			}
		}
		token->field=new char[i];
		strcpy(token->field,temp);
		return token;
	}
bool Lex::isCompare(char c)
{
	if(c=='='||c=='>'||c=='<')
		return true;
	else
		return false;
}
bool Lex::isBracket(char c)
{
	if(c=='('||c==')')
		return true;
	else
		return false;
}
Token* Lex::getToken()
{
    return token;
}

char Lex::getAt(char *p,int i)
{
	for(int j=0;j<i;j++)
		p++;
	char c=*p;
	return c;
}