scanner.c

#include "scanner.h"

// Palabras reservadas
const char* reserved_words[] = {
	"begin", "end" ,"read", "write"
};

line_t line_info = {1, 0};

token scanner(void){
	int in_char, c;
	clear_buffer(); //Limpia la estructura del token
	
	if(feof(source))
		return SCANEOF;

	while((in_char = getc(source)) != EOF){

		// Ignora los espacios de linea
		if(isspace(in_char)){
			if(in_char == '\n'){
				line_info.number++;
				line_info.offset = ftell(source);
			}
			continue;
		}
		// Identifica IDs y palabras reservadas
		else if(isalpha(in_char)){
			buffer_char(in_char);

			for(c = getc(source); isalnum(c) || c == '_'; c = getc(source))
				buffer_char(c);

			ungetc(c, source);
			return check_reserved();
		}
		// Identifica literales de tipo entero
		else if(isdigit(in_char)){
			buffer_char(in_char);
			
			for (c = getc(source); isdigit(c); c = getc(source))
				buffer_char(c);
			
			ungetc(c, source);
			return INTLITERAL;
		}
		// Identifica el paréntesis izquierdo
		else if(in_char == '('){
			buffer_char(in_char);
			return LPAREN;
		}
		// Identifica el paréntesis derecho
		else if(in_char == ')'){
			buffer_char(in_char);
			return RPAREN;
		}
		// Identifica el ; de cada instrucción
		else if(in_char == ';'){
			buffer_char(in_char);
			return SEMICOLON;
		}
		else if(in_char == ','){
			buffer_char(in_char);
			return COMMA;
		}
		else if(in_char == '+'){
			buffer_char(in_char);
			return PLUSOP;
		}
		else if(in_char == ':'){
			buffer_char(in_char);
			/* looking for ':=' */
			c = getc(source);
			if(c == '='){
				buffer_char(c);
				return ASSIGNOP;
			}
			else{
				ungetc(c, source);
				lexical_error(in_char);
			}
		} else if(in_char == '-'){
			/* looking for '--' */
			c = getc(source);
			if(c == '-'){
				while ((in_char = getc(source)) != '\n');
				line_info.number++;
				line_info.offset = ftell(source);
			} else if(isdigit(c)){
				
				buffer_char(in_char);
				buffer_char(c);
			
				for (c = getc(source); isdigit(c); c = getc(source))
					buffer_char(c);
			
				ungetc(c, source);
				return INTLITERAL;
			}else{
				buffer_char(in_char);
				ungetc(c, source);
				return MINUSOP;
			}
		} else if(in_char == '|'){
			buffer_char(in_char);
			return PIPEOP;
		}
		else{
			lexical_error(in_char);
		}	
	}
	return 0;
}

// Prepara el buffer donde se guarda el token
void buffer_char(char c){
	if(token_buffer.token != NULL){
		token_buffer.size++;
		token_buffer.token = (char *) realloc(token_buffer.token, token_buffer.size * sizeof(char));
	} else{
		token_buffer.token = (char *) calloc(token_buffer.size, sizeof(char));
		token_buffer.size = 1;
	}
	token_buffer.token[token_buffer.size - 1] = c;
}

// Limpia el buffer del token
void clear_buffer(){
	free(token_buffer.token);
	token_buffer.token = NULL;
}

// Verifica si es una palabra reservada o un identificador
token check_reserved(void){
	for (int i = 0; i < 4; ++i)
	{
		if(!strcmp(reserved_words[i], token_buffer.token)){
			switch(i){
				case 0:
					return BEGIN;
				case 1:
					return END;
				case 2:
					return READ;
				case 3:
					return WRITE;
			}
		}
	}
	return ID;
}