/
gettoken2.cpp
174 lines (148 loc) · 3.81 KB
/
gettoken2.cpp
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//
// gettoken.cpp
// p2lexer
//
// Created by Gerard Ryan on 2/26/15.
// Copyright (c) 2015 Gerard Ryan. All rights reserved.
//
#include "p2lex.h"
#include <cctype>
#include <cstdlib>
enum LexState {
START,
INID,
ININT,
INSTRING,
INCOMMENT,
ONESLASH
};
inline Token
keywordCheck(const string& word)
{
if (word == "set") {
return SET;
}
else if (word == "print") {
return PRINT;
}
return ID;
}
int currLine = 1;
static bool pushedBack = false;
static Token pushedToken;
static string pushedLexeme;
bool
pushbackToken(Token t, string lexeme)
{
if( pushedBack ) return false; // cannot push more than 1
pushedToken = t;
pushedLexeme = lexeme;
pushedBack = true;
return true;
}
Token
getToken(istream *br, string& lexeme)
{
if( pushedBack ) {
pushedBack = false;
lexeme = pushedLexeme;
return pushedToken;
}
LexState state = START;
lexeme.clear();
int inchar;
while ( (inchar = br->get()) ) {
if( inchar == '\n' ) currLine++;
switch (state) {
case START:
if (isspace(inchar)) {
continue;
}
lexeme += inchar;
if (inchar == '+') {
return PLUS;
}
if (inchar == '-') {
return MINUS;
}
if (inchar == '*') {
return STAR;
}
if (inchar == ';') {
return SC;
}
if (inchar == '/') {
state = ONESLASH;
}
else if (inchar == '"') {
state = INSTRING;
}
else if (isdigit(inchar)) {
state = ININT;
}
else if (isalpha(inchar)) {
state = INID;
}
else
return DONE;
break;
case INID:
if (isalpha(inchar)) {
lexeme += inchar;
continue;
}
br->putback(inchar);
return keywordCheck(lexeme);
break;
case ININT:
if (isdigit(inchar)) {
lexeme += inchar;
continue;
}
br->putback(inchar);
return INT;
break;
case INSTRING:
lexeme += inchar;
if (inchar == '\n') {
return DONE;
}
if (inchar != '"') {
continue;
}
return STRING;
break;
case INCOMMENT:
if (inchar != '\n') {
continue;
}
state = START;
break;
case ONESLASH:
if (inchar != '/') {
br->putback(inchar);
return SLASH;
}
lexeme.clear();
state = INCOMMENT;
break;
default:
cerr << "This should never happen!" << endl;
exit(1);
break;
}
}
// I reached an end of file... perhaps it happened in the middle of something...
if (state == INID) {
return keywordCheck(lexeme);
}
else if (state == ININT) {
return INT;
}
else if (state == ONESLASH) {
return SLASH;
}
else {
return DONE;
}
}