/*!
* common.js - mining utils
* Copyright (c) 2014-2017, Christopher Jeffrey (MIT License).
* https://github.com/bcoin-org/bcoin
*/
'use strict';
const assert = require('bsert');
const consensus = require('../protocol/consensus');
const BN = require('bcrypto/lib/bn.js');
/**
* @exports mining/common
*/
const common = exports;
/*
* Constants
*/
const DIFF = 0x00000000ffff0000000000000000000000000000000000000000000000000000;
const B192 = 0x1000000000000000000000000000000000000000000000000;
const B128 = 0x100000000000000000000000000000000;
const B64 = 0x10000000000000000;
const B0 = 0x1;
/**
* Swap 32 bit endianness of uint256.
* @param {Buffer} data
* @returns {Buffer}
*/
common.swap32 = function swap32(data) {
for (let i = 0; i < data.length; i += 4) {
const field = data.readUInt32LE(i, true);
data.writeUInt32BE(field, i, true);
}
return data;
};
/**
* Compare two uint256le's.
* @param {Buffer} a
* @param {Buffer} b
* @returns {Number}
*/
common.rcmp = function rcmp(a, b) {
assert(a.length === b.length);
for (let i = a.length - 1; i >= 0; i--) {
if (a[i] < b[i])
return -1;
if (a[i] > b[i])
return 1;
}
return 0;
};
/**
* Convert a uint256le to a double.
* @param {Buffer} target
* @returns {Number}
*/
common.double256 = function double256(target) {
let n = 0;
let hi, lo;
assert(target.length === 32);
hi = target.readUInt32LE(28, true);
lo = target.readUInt32LE(24, true);
n += (hi * 0x100000000 + lo) * B192;
hi = target.readUInt32LE(20, true);
lo = target.readUInt32LE(16, true);
n += (hi * 0x100000000 + lo) * B128;
hi = target.readUInt32LE(12, true);
lo = target.readUInt32LE(8, true);
n += (hi * 0x100000000 + lo) * B64;
hi = target.readUInt32LE(4, true);
lo = target.readUInt32LE(0, true);
n += (hi * 0x100000000 + lo) * B0;
return n;
};
/**
* Calculate mining difficulty
* from little-endian target.
* @param {Buffer} target
* @returns {Number}
*/
common.getDifficulty = function getDifficulty(target) {
const d = DIFF;
const n = common.double256(target);
if (n === 0)
return d;
return Math.floor(d / n);
};
/**
* Get target from bits as a uint256le.
* @param {Number} bits
* @returns {Buffer}
*/
common.getTarget = function getTarget(bits) {
const target = consensus.fromCompact(bits);
if (target.isNeg())
throw new Error('Target is negative.');
if (target.isZero())
throw new Error('Target is zero.');
return target.toArrayLike(Buffer, 'le', 32);
};
/**
* Get bits from target.
* @param {Buffer} data
* @returns {Buffer}
*/
common.getBits = function getBits(data) {
const target = new BN(data, 'le');
if (target.isZero())
throw new Error('Target is zero.');
return consensus.toCompact(target);
};