@woosh/meep-engine/src/core/parser/simple/readStringToken.js

Pure JavaScript game engine. Fully featured and production ready.

import { assert } from "../../assert.js";
import DataType from "./DataType.js";
import ParserError from "./ParserError.js";
import Token from "./Token.js";
import TokenType from "./TokenType.js";

/**
 *
 * @param {string} text
 * @param {number} cursor
 * @returns {string}
 */
function readQuote(text, cursor) {
    const char = text.charAt(cursor);

    if (char !== '"' && char !== '\'') {
        throw new ParserError(cursor, "Expected \", found " + char + " instead", text);
    }

    return char;
}

/**
 *
 * @param {string} text
 * @param {number} cursor
 * @param {number} length
 * @returns {Token}
 */
export function readStringToken(text, cursor, length) {
    assert.isString(text, 'text');
    assert.isNonNegativeInteger(cursor, 'cursor');
    assert.isNonNegativeInteger(length, 'length');

    let i = cursor;

    const openingQuote = readQuote(text, i);

    i++;

    let char;

    let value = '';
    const lastPossibleChar = length - 1;

    for (; i < lastPossibleChar; i++) {
        char = text.charAt(i);

        if (char === '\\') {
            i++;
            //read escape sequence
            char = text.charAt(i);

            switch (char) {
                case 'n':
                    value += '\n';
                    break;
                case 't':
                    value += '\t';
                    break;
                case 'r':
                    value += '\r';
                    break;
                case 'b':
                    value += '\b';
                    break;
                case 'f':
                    value += '\f';
                    break;
                case 'v':
                    value += '\v';
                    break;
                case '0':
                    value += '\0';
                    break;
                case '\\':
                case "'":
                case '"':
                default:
                    value += char;
                    break;
            }
        } else if (char !== openingQuote) {
            value += char;
        } else {
            break;
        }
    }

    char = text.charAt(i);

    if (char !== openingQuote) {
        throw new ParserError(cursor, "Expected string terminator : " + openingQuote + ", but found '" + char + "' instead", text);
    }

    i++;

    return new Token(value, cursor, i, TokenType.LiteralString, DataType.String);
}