User:Brooke Vibber/Gadget-ParserPlayground-HashMap.js

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/**
 * Very primitive hashmap class that allows using objects as keys;
 * JSON flattening of the key object is used as a hash code, so only
 * suitable for objects that will be immutable for now.
 *
 * Actual final comparison is done using object identity, but the
 * bucket match is from the JSON, so don't mess around!
 *
 * Used to map parse tree nodes to output nodes for the inspector mode.
 */
function HashMap() {
    this.keyBuckets = {};
    this.valBuckets = {};
}

/**
 * @param {object} keyObj
 * @return {object} original object, or null if no match found.
 */
HashMap.prototype.get = function(keyObj) {
    var key = this.hash(keyObj);
    if (typeof this.keyBuckets[key] !== 'undefined') {
        var keys = this.keyBuckets[key],
            max = keys.length;
        for (var i = 0; i < max; i++) {
            if (keyObj === keys[i]) {
                return this.valBuckets[key][i];
            }
        }
    }
    return null;
};

/**
 * @param {object} keyObj
 * @param {object} val
 */
HashMap.prototype.put = function(keyObj, val) {
    var key = this.hash(keyObj);
    if (typeof this.keyBuckets[key] === 'undefined') {
        this.keyBuckets[key] = [];
        this.valBuckets[key] = [];
    }
    this.keyBuckets[key].push(keyObj);
    this.valBuckets[key].push(val);
};

/**
 * This will do for us for now. :)
 */
HashMap.prototype.hash = function(keyObj) {
    return JSON.stringify(keyObj).substr(0, 40);
};