diffusion/src/node_modules/cbor/context.js

Diffusion JavaScript client

/*eslint valid-jsdoc: "off"*/

/**
 * Maintain recursive parsing context on a stack.
 */
function Context() {
    var ROOT = { length : -1, type : 'root', read : 0 };
    var stack = [];
    var tail = ROOT;

    /**
     * @returns {Object} the type of the current context
     */
    this.type = function() {
        return tail.type;
    };

    /**
     * @returns {Number} how many tokens have been read in this context
     */
    this.read = function() {
        return tail.read;
    };

    /**
     * @returns {Number} how many tokens are expected by this current context
     */
    this.expected = function() {
        return tail.length;
    };

    /**
     * Add a new context
     */
    this.push = function(type, length) {
        length = length === undefined ? -1 : length;

        tail = {
            length : length,
            type : type,
            read : 0
        };

        stack.push(tail);
    };

    /**
     * Pop the current context
     *
     * @returns the previous tail on the context stack
     */
    this.pop = function() {
        var prev = stack.pop();

        if (stack.length) {
            tail = stack[stack.length - 1];
        } else {
            tail = ROOT;
        }

        return prev;
    };

    /**
     * Progress through the current context's expected value count
     */
    this.next = function() {
        if (this.hasRemaining()) {
            tail.read++;
        } else {
            throw new Error('Exceeded expected collection limit');
        }
    };

    /**
     * Ends this current context.
     */
    this.break = function() {
        if (this.acceptsBreakMarker()) {
            tail.length = 0;
            tail.read = 0;
        }
    };

    /**
     * @returns {Number} the expected number of remaining values from the current context.
     */
    this.hasRemaining = function() {
        return tail.length === -1 ? true : tail.length > tail.read;
    };

    /**
     * @returns {Boolean} whether the current context accepts break marker tokens
     */
    this.acceptsBreakMarker = function() {
        return tail !== ROOT && tail.length === -1;
    };
}

module.exports = Context;