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diff --git a/node_modules/bn.js/README.md b/node_modules/bn.js/README.md new file mode 100644 index 0000000..83030ba --- /dev/null +++ b/node_modules/bn.js/README.md @@ -0,0 +1,228 @@ +# <img src="./logo.png" alt="bn.js" width="160" height="160" /> + +> BigNum in pure javascript + +[](http://travis-ci.org/indutny/bn.js) + +## Install +`npm install --save bn.js` + +## Usage + +```js +const BN = require('bn.js'); + +var a = new BN('dead', 16); +var b = new BN('101010', 2); + +var res = a.add(b); +console.log(res.toString(10)); // 57047 +``` + +**Note**: decimals are not supported in this library. + +## Notation + +### Prefixes + +There are several prefixes to instructions that affect the way the work. Here +is the list of them in the order of appearance in the function name: + +* `i` - perform operation in-place, storing the result in the host object (on + which the method was invoked). Might be used to avoid number allocation costs +* `u` - unsigned, ignore the sign of operands when performing operation, or + always return positive value. Second case applies to reduction operations + like `mod()`. In such cases if the result will be negative - modulo will be + added to the result to make it positive + +### Postfixes + +* `n` - the argument of the function must be a plain JavaScript + Number. Decimals are not supported. +* `rn` - both argument and return value of the function are plain JavaScript + Numbers. Decimals are not supported. + +### Examples + +* `a.iadd(b)` - perform addition on `a` and `b`, storing the result in `a` +* `a.umod(b)` - reduce `a` modulo `b`, returning positive value +* `a.iushln(13)` - shift bits of `a` left by 13 + +## Instructions + +Prefixes/postfixes are put in parens at the of the line. `endian` - could be +either `le` (little-endian) or `be` (big-endian). + +### Utilities + +* `a.clone()` - clone number +* `a.toString(base, length)` - convert to base-string and pad with zeroes +* `a.toNumber()` - convert to Javascript Number (limited to 53 bits) +* `a.toJSON()` - convert to JSON compatible hex string (alias of `toString(16)`) +* `a.toArray(endian, length)` - convert to byte `Array`, and optionally zero + pad to length, throwing if already exceeding +* `a.toArrayLike(type, endian, length)` - convert to an instance of `type`, + which must behave like an `Array` +* `a.toBuffer(endian, length)` - convert to Node.js Buffer (if available). For + compatibility with browserify and similar tools, use this instead: + `a.toArrayLike(Buffer, endian, length)` +* `a.bitLength()` - get number of bits occupied +* `a.zeroBits()` - return number of less-significant consequent zero bits + (example: `1010000` has 4 zero bits) +* `a.byteLength()` - return number of bytes occupied +* `a.isNeg()` - true if the number is negative +* `a.isEven()` - no comments +* `a.isOdd()` - no comments +* `a.isZero()` - no comments +* `a.cmp(b)` - compare numbers and return `-1` (a `<` b), `0` (a `==` b), or `1` (a `>` b) + depending on the comparison result (`ucmp`, `cmpn`) +* `a.lt(b)` - `a` less than `b` (`n`) +* `a.lte(b)` - `a` less than or equals `b` (`n`) +* `a.gt(b)` - `a` greater than `b` (`n`) +* `a.gte(b)` - `a` greater than or equals `b` (`n`) +* `a.eq(b)` - `a` equals `b` (`n`) +* `a.toTwos(width)` - convert to two's complement representation, where `width` is bit width +* `a.fromTwos(width)` - convert from two's complement representation, where `width` is the bit width +* `BN.isBN(object)` - returns true if the supplied `object` is a BN.js instance +* `BN.max(a, b)` - return `a` if `a` bigger than `b` +* `BN.min(a, b)` - return `a` if `a` less than `b` + +### Arithmetics + +* `a.neg()` - negate sign (`i`) +* `a.abs()` - absolute value (`i`) +* `a.add(b)` - addition (`i`, `n`, `in`) +* `a.sub(b)` - subtraction (`i`, `n`, `in`) +* `a.mul(b)` - multiply (`i`, `n`, `in`) +* `a.sqr()` - square (`i`) +* `a.pow(b)` - raise `a` to the power of `b` +* `a.div(b)` - divide (`divn`, `idivn`) +* `a.mod(b)` - reduct (`u`, `n`) (but no `umodn`) +* `a.divRound(b)` - rounded division + +### Bit operations + +* `a.or(b)` - or (`i`, `u`, `iu`) +* `a.and(b)` - and (`i`, `u`, `iu`, `andln`) (NOTE: `andln` is going to be replaced + with `andn` in future) +* `a.xor(b)` - xor (`i`, `u`, `iu`) +* `a.setn(b)` - set specified bit to `1` +* `a.shln(b)` - shift left (`i`, `u`, `iu`) +* `a.shrn(b)` - shift right (`i`, `u`, `iu`) +* `a.testn(b)` - test if specified bit is set +* `a.maskn(b)` - clear bits with indexes higher or equal to `b` (`i`) +* `a.bincn(b)` - add `1 << b` to the number +* `a.notn(w)` - not (for the width specified by `w`) (`i`) + +### Reduction + +* `a.gcd(b)` - GCD +* `a.egcd(b)` - Extended GCD results (`{ a: ..., b: ..., gcd: ... }`) +* `a.invm(b)` - inverse `a` modulo `b` + +## Fast reduction + +When doing lots of reductions using the same modulo, it might be beneficial to +use some tricks: like [Montgomery multiplication][0], or using special algorithm +for [Mersenne Prime][1]. + +### Reduction context + +To enable this tricks one should create a reduction context: + +```js +var red = BN.red(num); +``` +where `num` is just a BN instance. + +Or: + +```js +var red = BN.red(primeName); +``` + +Where `primeName` is either of these [Mersenne Primes][1]: + +* `'k256'` +* `'p224'` +* `'p192'` +* `'p25519'` + +Or: + +```js +var red = BN.mont(num); +``` + +To reduce numbers with [Montgomery trick][0]. `.mont()` is generally faster than +`.red(num)`, but slower than `BN.red(primeName)`. + +### Converting numbers + +Before performing anything in reduction context - numbers should be converted +to it. Usually, this means that one should: + +* Convert inputs to reducted ones +* Operate on them in reduction context +* Convert outputs back from the reduction context + +Here is how one may convert numbers to `red`: + +```js +var redA = a.toRed(red); +``` +Where `red` is a reduction context created using instructions above + +Here is how to convert them back: + +```js +var a = redA.fromRed(); +``` + +### Red instructions + +Most of the instructions from the very start of this readme have their +counterparts in red context: + +* `a.redAdd(b)`, `a.redIAdd(b)` +* `a.redSub(b)`, `a.redISub(b)` +* `a.redShl(num)` +* `a.redMul(b)`, `a.redIMul(b)` +* `a.redSqr()`, `a.redISqr()` +* `a.redSqrt()` - square root modulo reduction context's prime +* `a.redInvm()` - modular inverse of the number +* `a.redNeg()` +* `a.redPow(b)` - modular exponentiation + +### Number Size + +Optimized for elliptic curves that work with 256-bit numbers. +There is no limitation on the size of the numbers. + +## LICENSE + +This software is licensed under the MIT License. + +Copyright Fedor Indutny, 2015. + +Permission is hereby granted, free of charge, to any person obtaining a +copy of this software and associated documentation files (the +"Software"), to deal in the Software without restriction, including +without limitation the rights to use, copy, modify, merge, publish, +distribute, sublicense, and/or sell copies of the Software, and to permit +persons to whom the Software is furnished to do so, subject to the +following conditions: + +The above copyright notice and this permission notice shall be included +in all copies or substantial portions of the Software. + +THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS +OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF +MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN +NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, +DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR +OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE +USE OR OTHER DEALINGS IN THE SOFTWARE. + +[0]: https://en.wikipedia.org/wiki/Montgomery_modular_multiplication +[1]: https://en.wikipedia.org/wiki/Mersenne_prime |