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lex.c
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/**
* School project to subject IFJ (Formal Languages and Compilers)
* Compiler implementation of imperative language IFJ18
*
* Module for lexical analysis
*
* Author: Martin Rockar
* Login: xrocka00
*/
#include<stdio.h>
#include<stdlib.h>
#include<ctype.h>
#include <string.h>
#include "lex.h"
#include "error.h"
/**
* Function compares string with reserved keywords,
* if there is a match,function returns value of a reserved word.
* @param *tmp string to compare
* @return value of a keyword or -1 if it is an identifier
*/
int checkKeywords(char *tmp) {
if (strcmp("def", tmp) == 0) return KEYWORD_DEF;
else if (strcmp("do", tmp) == 0) return KEYWORD_DO;
else if (strcmp("else", tmp) == 0) return KEYWORD_ELSE;
else if (strcmp("end", tmp) == 0) return KEYWORD_END;
else if (strcmp("if", tmp) == 0) return KEYWORD_IF;
else if (strcmp("not", tmp) == 0) return KEYWORD_NOT;
else if (strcmp("nil", tmp) == 0) return KEYWORD_NIL;
else if (strcmp("then", tmp) == 0) return KEYWORD_THEN;
else if (strcmp("while", tmp) == 0) return KEYWORD_WHILE;
else if (strcmp("inputs", tmp) == 0) return INPUTS;
else if (strcmp("inputf", tmp) == 0) return INPUTF;
else if (strcmp("inputi", tmp) == 0) return INPUTI;
else if (strcmp("print", tmp) == 0) return PRINT;
else if (strcmp("ord", tmp) == 0) return ORD;
else if (strcmp("chr", tmp) == 0) return CHR;
else if (strcmp("substr", tmp) == 0) return SUBSTR;
else if (strcmp("length", tmp) == 0) return LENGTH;
else return -1;
}
int prev_token = -1;
/**
* Function stores previous token, if there is no token stored, function getTokenFromInput is called.
* @param value value of a token
* @return previous token or calls function getTokenFromInput
*/
int getToken(string *value) {
if (prev_token != -1) {
int temp = prev_token;
prev_token = -1;
return temp;
}
return getTokenFromInput(value);
}
/**
* Main function of a scanner, this function read characters from stdin and transform
* them into lexems(tokens)
* @param value value of a token
* @return type of a token represented by integer number.
*/
int getTokenFromInput(string *value) {
int s, state = START;
int res = 0;
int resTmp[4] = {0, 0, 0, '\0'};
static int isFirstToken = 1;
strClear(value);
while (1) {
s = fgetc(stdin);
if (s == EOF) {
if (state == START) {
return LEX_EOF;
}
}
switch (state) {
//main switch for states
case START:
if (isFirstToken) {
if (isFirstToken) {
isFirstToken = 0;
}
if (s == '=') {
while (!isspace(s)) {
strAddChar(value, s);
if (value->length > 6) {
return ERR_LEXICAL;
}
s = fgetc(stdin);
}
if (strcmp(value->str, "=begin") == 0) {
state = BLOCK_COMMENT;
break;
} else {
return ERR_LEXICAL;
}
}
}
if (s == '\n') {
s = fgetc(stdin);
if (s == '=') {
while (!isspace(s)) {
strAddChar(value, s);
if (value->length > 6) {
return ERR_LEXICAL;
}
s = fgetc(stdin);
}
if (strcmp(value->str, "=begin") == 0) {
state = BLOCK_COMMENT;
break;
} else {
return ERR_LEXICAL;
}
} else {
ungetc(s, stdin);
return LEX_EOL;
}
} else if (isspace(s)); //skip white spaces
else if (islower(s) || s == '_') {
strAddChar(value, s);
s = fgetc(stdin);
if (isalnum(s) || s == '_' || s == '?' || s == '!') {
ungetc(s, stdin);
state = IDENTIF;
} else {
ungetc(s, stdin);
return ID;
}
break;
} else if (isdigit(s)) {
strAddChar(value, s);
if (s == '0') {
//check if first number of an multi digit number is not 0
s = fgetc(stdin);
if (isdigit(s)) {
return ERR_LEXICAL;
} else {
ungetc(s, stdin);
}
}
state = NUM;
break;
} else {
switch (s) {
//switch for operators
case '+':
return PLUS;
case '-':
return MINUS;
case '*':
return MUL;
case '/':
return DIV;
case '<':
s = fgetc(stdin);
if (s == '=') {
return LESS_EQUAL;
} else {
ungetc(s, stdin);
return LESS;
}
case '>':
s = fgetc(stdin);
if (s == '=') {
return MORE_EQUAL;
} else {
ungetc(s, stdin);
return MORE;
}
case '(':
return ROUNDL;
case ')':
return ROUNDR;
case ',':
return COMMA;
case '"':
state = STRING;
break;
case '#':
//line comment
s = fgetc(stdin);
while (s != '\n') {
if (s == EOF)
return LEX_EOF;
s = fgetc(stdin);
}
return LEX_EOL;
case '=':
s = fgetc(stdin);
if (s == '=') {
return EQUAL;
} else {
ungetc(s, stdin);
return ASSIGN;
}
case '!':
s = fgetc(stdin);
if (s == '=')
return NOT_EQUAL;
ungetc(s, stdin);
return ERR_LEXICAL;
default:
return ERR_LEXICAL;
}
}
break;
case STRING:
if (s == '#') {
strAddChar(value, '\\');
strAddChar(value, '0');
strAddChar(value, '3');
strAddChar(value, '5');
} else if (s == '\\') {
//escape sequence
s = fgetc(stdin);
if (s == '"') {
strAddChar(value, '\\');
strAddChar(value, '0');
strAddChar(value, '3');
strAddChar(value, '4');
} else if (s == 'n') {
strAddChar(value, '\\');
strAddChar(value, '0');
strAddChar(value, '1');
strAddChar(value, '0');
} else if (s == 't') {
strAddChar(value, '\\');
strAddChar(value, '0');
strAddChar(value, '0');
strAddChar(value, '9');
} else if (s == 's') {
strAddChar(value, '\\');
strAddChar(value, '0');
strAddChar(value, '3');
strAddChar(value, '2');
} else if (s == '\\') {
strAddChar(value, '\\');
strAddChar(value, '0');
strAddChar(value, '9');
strAddChar(value, '2');
} else if (s == 'x') {
//hexadecimal escape sequence
s = fgetc(stdin);
if (s >= 65 && s <= 70) {
res = ((s - 'A') + 10);
} else if (s >= 97 && s <= 102) {
res = ((s - 'a') + 10);
} else if (isdigit(s)) {
res = s - '0';
} else return ERR_LEXICAL;
s = fgetc(stdin);
if (s >= 65 && s <= 70) {
res = res * 16 + ((s - 'A') + 10);
} else if (s >= 97 && s <= 102) {
res = res * 16 + ((s - 'a') + 10);
} else if (isdigit(s)) {
res = res * 16 + (s - '0');
} else ungetc(s, stdin);
strAddChar(value, '\\');
resTmp[0] = res % 10 + '0';
res /= 10;
resTmp[1] = res % 10 + '0';
res /= 10;
resTmp[2] = res % 10 + '0';
strAddChar(value, resTmp[2]);
strAddChar(value, resTmp[1]);
strAddChar(value, resTmp[0]);
} else {
ungetc(s, stdin);
}
} else if (s == ' ') {
strAddChar(value, '\\');
strAddChar(value, '0');
strAddChar(value, '3');
strAddChar(value, '2');
} else if (s == '"') {
return STRING;
} else strAddChar(value, s);
while (1) {
s = fgetc(stdin);
if (s == '#') {
strAddChar(value, '\\');
strAddChar(value, '0');
strAddChar(value, '3');
strAddChar(value, '5');
} else if (s == '\\') {
//escape sequence
s = fgetc(stdin);
if (s == '"') {
strAddChar(value, '\\');
strAddChar(value, '0');
strAddChar(value, '3');
strAddChar(value, '4');
} else if (s == 'n') {
strAddChar(value, '\\');
strAddChar(value, '0');
strAddChar(value, '1');
strAddChar(value, '0');
} else if (s == 't') {
strAddChar(value, '\\');
strAddChar(value, '0');
strAddChar(value, '0');
strAddChar(value, '9');
} else if (s == 's') {
strAddChar(value, '\\');
strAddChar(value, '0');
strAddChar(value, '3');
strAddChar(value, '2');
} else if (s == '\\') {
strAddChar(value, '\\');
strAddChar(value, '0');
strAddChar(value, '9');
strAddChar(value, '2');
} else if (s == 'x') {
//hexadecimal escape sequence
s = fgetc(stdin);
if (isupper(s)) {
res = ((s - 'A') + 10);
} else if (islower(s)) {
res = ((s - 'a') + 10);
} else if (isdigit(s)) {
res = s - '0';
} else if (!isalpha(s)) return ERR_LEXICAL;
s = fgetc(stdin);
if (isupper(s)) {
res = res * 16 + ((s - 'A') + 10);
} else if (islower(s)) {
res = res * 16 + ((s - 'a') + 10);
} else if (isdigit(s)) {
res = res * 16 + (s - '0');
} else ungetc(s, stdin);
strAddChar(value, '\\');
resTmp[0] = res % 10 + '0';
res /= 10;
resTmp[1] = res % 10 + '0';
res /= 10;
resTmp[2] = res % 10 + '0';
strAddChar(value, resTmp[2]);
strAddChar(value, resTmp[1]);
strAddChar(value, resTmp[0]);
} else {
ungetc(s, stdin);
}
} else if (s == ' ') {
strAddChar(value, '\\');
strAddChar(value, '0');
strAddChar(value, '3');
strAddChar(value, '2');
} else if (s == EOF) {
return ERR_LEXICAL;
} else if (s == '"') {
return STRING;
} else {
strAddChar(value, s);
}
//printf("value: %s\n",value->str);
}
case IDENTIF:
if (isalnum(s) || s == '_' || s == '?' || s == '!') {
while (isalnum(s) || s == '_') {
strAddChar(value, s);
s = fgetc(stdin);
}
if (s == '?' || s == '!') {
strAddChar(value, s);
s = fgetc(stdin);
if (isalpha(s)) {
while (isalpha(s)) {
strAddChar(value, s);
s = fgetc(stdin);
}
return ERR_LEXICAL;
} else {
ungetc(s, stdin);
}
} else {
ungetc(s, stdin);
}
int a = checkKeywords(value->str); //checks if string is a reserved word or an identifier
if (a == -1) {
if (value->str[value->length - 1] == '?' || value->str[value->length - 1] == '!')
return IDF;
return ID;
} else {
return a;
}
}
break;
case BLOCK_COMMENT:
//checking for end of a block comment (=end) in input
while (1) {
if (s == '\n') {
s = fgetc(stdin);
if (s == '=') {
s = fgetc(stdin);
if (s == 'e') {
s = fgetc(stdin);
if (s == 'n') {
s = fgetc(stdin);
if (s == 'd') {
s = fgetc(stdin);
if (s == ' ' || s == '\t') {
while ((s = fgetc(stdin)) != '\n') {
if (s == EOF)
return ERR_LEXICAL;
}
}
return (s == '\n') ? LEX_EOL : ERR_LEXICAL;
}
}
}
}
}
s = fgetc(stdin);
if (s == EOF) {
return ERR_LEXICAL;
}
}
case NUM:
while (isdigit(s)) {
strAddChar(value, s);
s = fgetc(stdin);
}
if (s == '.') {
strAddChar(value, s);
state = NUM_FLOAT;
break;
} else if (s == 'e' || s == 'E') {
strAddChar(value, s);
state = NUM_EXP;
break;
} else if (isOperator(s) || isspace(s)) {
ungetc(s, stdin);
return NUM_INT;
} else {
return ERR_LEXICAL;
}
case NUM_FLOAT:
if (!isdigit(s)) {
return ERR_LEXICAL;
}
while (isdigit(s)) {
strAddChar(value, s);
s = fgetc(stdin);
}
if (s == 'e' || s == 'E') {
strAddChar(value, s);
state = NUM_EXP;
break;
} else {
ungetc(s, stdin);
return NUM_FLOAT;
}
case NUM_EXP:
if (s == '+' || s == '-') {
strAddChar(value, s);
s = fgetc(stdin);
}
if (!isdigit(s)) {
return ERR_LEXICAL;
}
while (isdigit(s)) {
strAddChar(value, s);
s = fgetc(stdin);
}
if (!isspace(s) && !isOperator(s))
return ERR_LEXICAL;
ungetc(s, stdin);
return NUM_EXP;
}
}
}
/**
* Function for checking if character is an operator.
* @param symbol character to check
* @return true if character is an operator, else it return false
*/
bool isOperator(int symbol) {
return ((symbol == '*' || symbol == '+' || symbol == '-' || symbol == '/' || symbol == ')') ||
(symbol == '<' || symbol == '>' || symbol == '=' || symbol == ',')) ? true : false;
}