bignum
Arbitrary-precision integer arithmetic using OpenSSL    Last updated a year ago by rvagg .
MIT · Repository · Bugs · Original npm · Tarball · package.json
`\$ cnpm install bignum `
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# bignum Arbitrary precision integral arithmetic for Node.js using OpenSSL.

This library is based on node-bigint by substack, but instead of using libgmp, it uses the builtin bignum functionality provided by OpenSSL. The advantage is that OpenSSL is already part of Node.js, so this library does not add any external dependency whatsoever.

# BigInt

JavaScript now has a BigInt object. If you are using Node 10.4 or newer, you should use or migrate to BigInt.

# differences

When switching from node-bigint to node-bignum, please be aware of these differences:

• Bignum rounds towards zero for integer divisions, e.g. `10 / -3 = -3`, whereas bigint rounds towards negative infinity, e.g. `10 / -3 = -4`.
• nextPrime() is not supported.
• sqrt() and root() are not supported.

(Patches for the missing functionality are welcome.)

# example

## simple.js

``````var bignum = require('bignum');

var b = bignum('782910138827292261791972728324982')
.sub('182373273283402171237474774728373')
.div(8)
;
console.log(b);
``````

``````\$ node simple.js
<Bignum 75067108192986261319312244199576>
``````

## perfect.js

Generate the perfect numbers:

``````// If 2**n-1 is prime, then (2**n-1) * 2**(n-1) is perfect.
var bignum = require('bignum');

for (var n = 0; n < 100; n++) {
var p = bignum.pow(2, n).sub(1);
if (p.probPrime(50)) {
var perfect = p.mul(bignum.pow(2, n - 1));
console.log(perfect.toString());
}
}
``````

``````6
28
496
8128
33550336
8589869056
137438691328
2305843008139952128
2658455991569831744654692615953842176
191561942608236107294793378084303638130997321548169216
``````

# methods

## bignum(n, base=10)

Create a new `bignum` from `n` and a base. `n` can be a string, integer, or another `bignum`.

If you pass in a string you can set the base that string is encoded in.

## .toString(base=10)

Print out the `bignum` instance in the requested base as a string.

## bignum.fromBuffer(buf, opts)

Create a new `bignum` from a `Buffer`.

The default options are:

``````{
endian : 'big',
size : 1, // number of bytes in each word
}
``````

Note that endian doesn't matter when size = 1. If you wish to reverse the entire buffer byte by byte, pass size: 'auto'.

## bignum.prime(bits, safe=true)

Generate a probable prime of length `bits`. If `safe` is true, it will be a "safe" prime of the form p=2p'+1 where p' is also prime.

## bignum.isBigNum(num)

Return true if `num` is identified as a bignum instance. Otherwise, return false.

# methods

For all of the instance methods below you can write either

``````bignum.method(x, y, z)
``````

or if x is a `bignum` instance``

``````x.method(y, z)
``````

## .toNumber()

Turn a `bignum` into a `Number`. If the `bignum` is too big you'll lose precision or you'll get ±`Infinity`.

## .toBuffer(opts)

Return a new `Buffer` with the data from the `bignum`.

The default options are:

``````{
endian : 'big',
size : 1, // number of bytes in each word
}
``````

Note that endian doesn't matter when size = 1. If you wish to reverse the entire buffer byte by byte, pass size: 'auto'.

Return a new `bignum` containing the instance value plus `n`.

## .sub(n)

Return a new `bignum` containing the instance value minus `n`.

## .mul(n)

Return a new `bignum` containing the instance value multiplied by `n`.

## .div(n)

Return a new `bignum` containing the instance value integrally divided by `n`.

## .abs()

Return a new `bignum` with the absolute value of the instance.

## .neg()

Return a new `bignum` with the negative of the instance value.

## .cmp(n)

Compare the instance value to `n`. Return a positive integer if `> n`, a negative integer if `< n`, and 0 if `== n`.

## .gt(n)

Return a boolean: whether the instance value is greater than n (`> n`).

## .ge(n)

Return a boolean: whether the instance value is greater than or equal to n (`>= n`).

## .eq(n)

Return a boolean: whether the instance value is equal to n (`== n`).

## .lt(n)

Return a boolean: whether the instance value is less than n (`< n`).

## .le(n)

Return a boolean: whether the instance value is less than or equal to n (`<= n`).

## .and(n)

Return a new `bignum` with the instance value bitwise AND (&)-ed with `n`.

## .or(n)

Return a new `bignum` with the instance value bitwise inclusive-OR (|)-ed with `n`.

## .xor(n)

Return a new `bignum` with the instance value bitwise exclusive-OR (^)-ed with `n`.

## .mod(n)

Return a new `bignum` with the instance value modulo `n`.

## `m`. .pow(n)

Return a new `bignum` with the instance value raised to the `n`th power.

## .powm(n, m)

Return a new `bignum` with the instance value raised to the `n`th power modulo `m`.

## .invertm(m)

Compute the multiplicative inverse modulo `m`.

## .rand(upperBound)

If `upperBound` is supplied, return a random `bignum` between the instance value and `upperBound - 1`, inclusive.

Otherwise, return a random `bignum` between 0 and the instance value - 1, inclusive.

## .probPrime()

Return whether the bignum is:

• certainly prime (true)
• probably prime ('maybe')
• certainly composite (false)

using BN_is_prime_ex.

## .sqrt()

Return a new `bignum` that is the square root. This truncates.

## .root(n)

Return a new `bignum` that is the `nth` root. This truncates.

## .shiftLeft(n)

Return a new `bignum` that is the `2^n` multiple. Equivalent of the `<<` operator.

## .shiftRight(n)

Return a new `bignum` of the value integer divided by `2^n`. Equivalent of the `>>` operator.

## .gcd(n)

Return the greatest common divisor of the current `bignum` with `n` as a new `bignum`.

## .jacobi(n)

Return the Jacobi symbol (or Legendre symbol if `n` is prime) of the current `bignum` (= a) over `n`. Note that `n` must be odd and >= 3. 0 <= a < n.

Returns -1 or 1 as an int (NOT a bignum). Throws an error on failure.

## .bitLength()

Return the number of bits used to represent the current `bignum`.

# install

To compile the package, your system needs to be set up for building Node.js modules.

You can install node-bignum with npm:

``````npm install bignum
``````

# develop

You can clone the git repo and compile with

``````git clone git://github.com/justmoon/node-bignum.git
cd node-bignum
npm install
``````

Run the tests with

``````npm test
``````

## Current Tags

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