hash.ts

//================================================================ 
/**
 * @packageDocumentation
 * @module std  
 */
//================================================================
import { IComparable } from "./IComparable";
import { get_uid } from "./uid";

/**
 * Hash function.
 * 
 * @param items The items to be hashed.
 * @return The hash code.
 */
export function hash(...items: any[]): number
{
    let ret: number = INIT_VALUE;
    
    for (let item of items)
    {
        item = item ? item.valueOf() : item;
        let type: string = typeof item;

        if (type === "boolean") // BOOLEAN -> 1 BYTE
            ret = _Hash_boolean(item, ret);
        else if (type === "number" || type === "bigint") // NUMBER -> 8 BYTES
            ret = _Hash_number(item, ret);
        else if (type === "string") // STRING -> {LENGTH} BYTES
            ret = _Hash_string(item, ret);
        else if (item instanceof Object && (<any>item as IComparable<{}>).hashCode instanceof Function)
        {
            let hashed: number = (<any>item as IComparable<{}>).hashCode();
            if (items.length === 1)
                return hashed;
            else
            {
                ret = ret ^ hashed;
                ret *= MULTIPLIER;
            }
        }
        else // object | null | undefined
            ret = _Hash_number(get_uid(item), ret);
    }
    return Math.abs(ret);
}

function _Hash_boolean(val: boolean, ret: number): number
{
    ret ^= val ? 1 : 0;
    ret *= MULTIPLIER;

    return ret;
}

function _Hash_number(val: number, ret: number): number
{
    return _Hash_string(val.toString(), ret);
    // // ------------------------------------------
    // //    IN C++
    // //        CONSIDER A NUMBER AS A STRING
    // //        HASH<STRING>((CHAR*)&VAL, 8)
    // // ------------------------------------------
    // // CONSTRUCT BUFFER AND BYTE_ARRAY
    // let buffer: ArrayBuffer = new ArrayBuffer(8);
    // let byteArray: Int8Array = new Int8Array(buffer);
    // let valueArray: Float64Array = new Float64Array(buffer);
    // valueArray[0] = val;

    // for (let i: number = 0; i < byteArray.length; ++i)
    // {
    //     let byte = (byteArray[i] < 0) ? byteArray[i] + 256 : byteArray[i];

    //     ret ^= byte;
    //     ret *= _HASH_MULTIPLIER;
    // }
    // return Math.abs(ret);
}

function _Hash_string(str: string, ret: number): number
{
    for (let i: number = 0; i < str.length; ++i)
    {
        ret ^= str.charCodeAt(i);
        ret *= MULTIPLIER;
    }
    return Math.abs(ret);
}

/* ---------------------------------------------------------
    RESERVED ITEMS
--------------------------------------------------------- */
const INIT_VALUE: number = 2166136261;
const MULTIPLIER: number = 16777619;