SafeMath.sol

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SafeMath.sol
View Source: contracts/SafeMath.sol​
Wrappers over Solidity's arithmetic operations with added overflow checks.
Arithmetic operations in Solidity wrap on overflow. This can easily result
in bugs, because programmers usually assume that an overflow raises an
error, which is the standard behavior in high level programming languages.
SafeMath restores this intuition by reverting the transaction when an
operation overflows.
Using this library instead of the unchecked operations eliminates an entire
class of bugs, so it's recommended to use it always.
Functions
add(uint256 a, uint256 b)
add(uint256 a, uint256 b, string errorMessage)
sub(uint256 a, uint256 b)
sub(uint256 a, uint256 b, string errorMessage)
mul(uint256 a, uint256 b)
mul(uint256 a, uint256 b, string errorMessage)
div(uint256 a, uint256 b)
div(uint256 a, uint256 b, string errorMessage)
mod(uint256 a, uint256 b)
mod(uint256 a, uint256 b, string errorMessage)
add
Returns the addition of two unsigned integers, reverting on overflow.
Counterpart to Solidity's + operator.
Requirements:
Addition cannot overflow.
1
function add(uint256 a, uint256 b) internal pure
2
returns(uint256)
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Arguments
Name
Type
Description
a
uint256
​
b
uint256
​
add
Returns the addition of two unsigned integers, reverting with custom message on overflow.
Counterpart to Solidity's + operator.
Requirements:
Addition cannot overflow.
1
function add(uint256 a, uint256 b, string errorMessage) internal pure
2
returns(uint256)
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Arguments
Name
Type
Description
a
uint256
​
b
uint256
​
errorMessage
string
​
sub
Returns the subtraction of two unsigned integers, reverting on underflow (when the result is negative).
Counterpart to Solidity's - operator.
Requirements:
Subtraction cannot underflow.
1
function sub(uint256 a, uint256 b) internal pure
2
returns(uint256)
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Arguments
Name
Type
Description
a
uint256
​
b
uint256
​
sub
Returns the subtraction of two unsigned integers, reverting with custom message on underflow (when the result is negative).
Counterpart to Solidity's - operator.
Requirements:
Subtraction cannot underflow.
1
function sub(uint256 a, uint256 b, string errorMessage) internal pure
2
returns(uint256)
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Arguments
Name
Type
Description
a
uint256
​
b
uint256
​
errorMessage
string
​
mul
Returns the multiplication of two unsigned integers, reverting on overflow.
Counterpart to Solidity's * operator.
Requirements:
Multiplication cannot overflow.
1
function mul(uint256 a, uint256 b) internal pure
2
returns(uint256)
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Arguments
Name
Type
Description
a
uint256
​
b
uint256
​
mul
Returns the multiplication of two unsigned integers, reverting on overflow.
Counterpart to Solidity's * operator.
Requirements:
Multiplication cannot overflow.
1
function mul(uint256 a, uint256 b, string errorMessage) internal pure
2
returns(uint256)
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Arguments
Name
Type
Description
a
uint256
​
b
uint256
​
errorMessage
string
​
div
Returns the integer division of two unsigned integers. Reverts on division by zero. The result is rounded towards zero.
Counterpart to Solidity's / operator. Note: this function uses a
revert opcode (which leaves remaining gas untouched) while Solidity
uses an invalid opcode to revert (consuming all remaining gas).
Requirements:
The divisor cannot be zero.
1
function div(uint256 a, uint256 b) internal pure
2
returns(uint256)
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Arguments
Name
Type
Description
a
uint256
​
b
uint256
​
div
Returns the integer division of two unsigned integers. Reverts with custom message on division by zero. The result is rounded towards zero.
Counterpart to Solidity's / operator. Note: this function uses a
revert opcode (which leaves remaining gas untouched) while Solidity
uses an invalid opcode to revert (consuming all remaining gas).
Requirements:
The divisor cannot be zero.
1
function div(uint256 a, uint256 b, string errorMessage) internal pure
2
returns(uint256)
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Arguments
Name
Type
Description
a
uint256
​
b
uint256
​
errorMessage
string
​
mod
Returns the remainder of dividing two unsigned integers. (unsigned integer modulo), Reverts when dividing by zero.
Counterpart to Solidity's % operator. This function uses a revert
opcode (which leaves remaining gas untouched) while Solidity uses an
invalid opcode to revert (consuming all remaining gas).
Requirements:
The divisor cannot be zero.
1
function mod(uint256 a, uint256 b) internal pure
2
returns(uint256)
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Arguments
Name
Type
Description
a
uint256
​
b
uint256
​
mod
Returns the remainder of dividing two unsigned integers. (unsigned integer modulo), Reverts with custom message when dividing by zero.
Counterpart to Solidity's % operator. This function uses a revert
opcode (which leaves remaining gas untouched) while Solidity uses an
invalid opcode to revert (consuming all remaining gas).
Requirements:
The divisor cannot be zero.
1
function mod(uint256 a, uint256 b, string errorMessage) internal pure
2
returns(uint256)
Copied!
Arguments
Name
Type
Description
a
uint256
​
b
uint256
​
errorMessage
string
​
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Functions