gnosis/solidity-arithmetic

Name: solidity-arithmetic

Owner: GNOSIS

Description: A solidity library for performing arithmetic.

Created: 2017-02-22 17:52:26.0

Updated: 2018-05-17 12:01:37.0

Pushed: 2017-03-09 15:16:02.0

Homepage: null

Size: 31

Language: JavaScript

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README

solidity-arithmetic

A solidity library for performing arithmetic.

Usage

The contract source is in the repo at contracts/Arithmetic.sol. Simply copy the contract file into your source tree and import it with:

rt "./path/to/Arithmetic.sol";

ract MyContract {
function myFunction() {
    uint a, b, d;
    // your code here
    uint result = Arithmetic.overflowResistantFraction(a, b, d);
}

library Arithmetic API

tion mul256By256(uint a, uint b)
constant
returns (uint ab32, uint ab1, uint ab0)

This function takes two unsigned 256-bit integers and multiplies them, returning a 512-bit result split into a high 256-bit limb, a middle 128-bit limb, and a low 128-bit limb.

tion div256_128By256(uint a21, uint a0, uint b)
constant
returns (uint q, uint r)

This function takes a unsigned 384-bit integer and divides it by a 256-bit integer, returning a high-bits truncated 256-bit quotient and a remainder. The 384-bit dividend is represented as a high 256-bit limb and a low 128-bit limb.

tion overflowResistantFraction(uint a, uint b, uint divisor)
returns (uint)

This function returns a 256-bit truncated a * b / divisor, where the division is integer division. The overflow from a * b is handled in a 512-bit buffer, so this method calculates the expression correctly for high values of a and b.