AgNES/scanner.cpp at master · taurheim/AgNES · GitHub

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#include <cctype>
#include <string.h>
#include <stdexcept>
#include "scanner.h"
#include "tokenMaps.h"
#include "util/tokenUtil.h"

Scanner::Scanner(std::ifstream & input)
    : input (input) {
    line = 0;
    pos = 0;
    ch = 0;
};

void Scanner::getChar() {
    input.get(ch);
    std::cout << ch;
}

Token Scanner::getNextToken() {
    Token sym;
    while (std::isspace(ch) && !input.eof()) getChar(); // skip to next non-whitespace character
    if (std::isalpha(ch)) {
        // Identifier
        sym = identifyKeyword();
    } else if (std::isdigit(ch)) {
        // Number
        sym = identifyNumber();
    } else if (ch == '\'') {
        // Char
        sym = identifyChar();
    } else if (input.eof()) {
        sym = { T_EOF_TOKEN };
    } else {
        sym = identifySpecialToken();
    }
    return sym;
}

Token Scanner::identifyKeyword() {
    std::string word;
    while (std::isalpha(ch)) { // create string... TODO: include numeric
        word += ch;
        getChar();
    }
    auto search = stringToToken.find(word);
    if (search == stringToToken.end()) {
        Token identToken;
        identToken.type = TokenType::T_IDENT;
        identToken.stringVal = word;
        return identToken;
    } else {
        return { search->second };
    }
}

Token Scanner::identifySpecialToken() {
    char firstChar = ch;
    getChar();
    switch (firstChar) {
        case '<': {
            if (ch == '=') {
                getChar();
                return Token(T_LESSEQUAL);
            }
        }
        case '>': {
            if (ch == '=') {
                getChar();
                return Token(T_GREATEREQUAL);
            }
        }
        case '&': {
            if (ch == '&') {
                getChar();
                return Token(T_AND);
            }
        }
        case '|' : {
            if (ch == '|') {
                getChar();
                return Token(T_OR);
            }
        }
        default: {
           break;
        }
    }
    auto search = charToToken.find(firstChar);
    if (search == charToToken.end()) {
        std::cerr << "Invalid character!";
        exit(1);
    }
    return { search->second };
}

Token Scanner::identifyNumber() {
    Token numberToken;
    numberToken.type = TokenType::T_INTVALUE;
    numberToken.intVal = 0;

    // Go through all the digits to get the full number
    while (std::isdigit(ch)) {
        numberToken.intVal = (numberToken.intVal * 10) + (ch - '0');
        getChar();
    }

    return numberToken;
}

Token Scanner::identifyChar() {
    if(ch != '\'') {
        reject("Char must begin with \"'\"");
    }

    getChar();
    Token charToken;
    charToken.type = TokenType::T_CHARVALUE;
    charToken.charVal = ch;
    getChar();

    if(ch != '\'') {
        reject("Char can only be of length 1, expected \"'\"");
    }
    getChar();

    return charToken;
}

std::list<Token> Scanner::scan() {
    std::cout << "Scanning...\n";
    getChar();

    std::list<Token> tokenList;
    while (true) {
        Token t = getNextToken();
        tokenList.push_back(t);

        if (t.type == T_EOF_TOKEN) break;
    }

    if (debug) {
        std::cout << "Scanner output: \n\t";
        for (auto const & i : tokenList) {
            std::cout << tokenToStr(i) << " ";
        }
        std::cout << std::endl;
    }

    return tokenList;
}

void Scanner::reject(std::string str) {
    std::cerr << std::endl << str << std::endl;
    exit(1);
}