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safemath.sol
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safemath.sol
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pragma solidity >=0.5.0 <0.6.0;
/**
* @title SafeMath
* @dev Math operations with safety checks that throw on error
*/
library SafeMath {
/**
* @dev Multiplies two numbers, throws on overflow.
*/
function mul(uint256 a, uint256 b) internal pure returns (uint256) {
if (a == 0) {
return 0;
}
uint256 c = a * b;
assert(c / a == b);
return c;
}
/**
* @dev Integer division of two numbers, truncating the quotient.
*/
function div(uint256 a, uint256 b) internal pure returns (uint256) {
// assert(b > 0); // Solidity automatically throws when dividing by 0
uint256 c = a / b;
// assert(a == b * c + a % b); // There is no case in which this doesn't hold
return c;
}
/**
* @dev Subtracts two numbers, throws on overflow (i.e. if subtrahend is greater than minuend).
*/
function sub(uint256 a, uint256 b) internal pure returns (uint256) {
assert(b <= a);
return a - b;
}
/**
* @dev Adds two numbers, throws on overflow.
*/
function add(uint256 a, uint256 b) internal pure returns (uint256) {
uint256 c = a + b;
assert(c >= a);
return c;
}
}
/**
* @title SafeMath32
* @dev SafeMath library implemented for uint32
*/
library SafeMath32 {
function mul(uint32 a, uint32 b) internal pure returns (uint32) {
if (a == 0) {
return 0;
}
uint32 c = a * b;
assert(c / a == b);
return c;
}
function div(uint32 a, uint32 b) internal pure returns (uint32) {
// assert(b > 0); // Solidity automatically throws when dividing by 0
uint32 c = a / b;
// assert(a == b * c + a % b); // There is no case in which this doesn't hold
return c;
}
function sub(uint32 a, uint32 b) internal pure returns (uint32) {
assert(b <= a);
return a - b;
}
function add(uint32 a, uint32 b) internal pure returns (uint32) {
uint32 c = a + b;
assert(c >= a);
return c;
}
}
/**
* @title SafeMath16
* @dev SafeMath library implemented for uint16
*/
library SafeMath16 {
function mul(uint16 a, uint16 b) internal pure returns (uint16) {
if (a == 0) {
return 0;
}
uint16 c = a * b;
assert(c / a == b);
return c;
}
function div(uint16 a, uint16 b) internal pure returns (uint16) {
// assert(b > 0); // Solidity automatically throws when dividing by 0
uint16 c = a / b;
// assert(a == b * c + a % b); // There is no case in which this doesn't hold
return c;
}
function sub(uint16 a, uint16 b) internal pure returns (uint16) {
assert(b <= a);
return a - b;
}
function add(uint16 a, uint16 b) internal pure returns (uint16) {
uint16 c = a + b;
assert(c >= a);
return c;
}
}
/*
assert(bool condition) causes a Panic error and thus state change reversion if the condition is not met - to be used for internal errors.
assert is similar to require, where it will throw an error if false. The difference between assert and require is that require will refund the user the rest of their gas when a function fails, whereas assert will not. So most of the time you want to use require in your code; assert is typically used when something has gone horribly wrong with the code (like a uint overflow).
So, simply put, SafeMath's add, sub, mul, and div are functions that do the basic 4 math operations, but throw an error if an overflow or underflow occurs.
*/