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Merge pull request #116 from aave/feat/gas-optimization-4
Feat/gas optimization 4
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@ -1,163 +1,49 @@
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// SPDX-License-Identifier: agpl-3.0
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pragma solidity 0.6.12;
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/**
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* @dev Wrappers over Solidity's arithmetic operations with added overflow
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* checks.
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*
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* Arithmetic operations in Solidity wrap on overflow. This can easily result
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* in bugs, because programmers usually assume that an overflow raises an
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* error, which is the standard behavior in high level programming languages.
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* `SafeMath` restores this intuition by reverting the transaction when an
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* operation overflows.
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*
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* Using this library instead of the unchecked operations eliminates an entire
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* class of bugs, so it's recommended to use it always.
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*/
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/// @title Optimized overflow and underflow safe math operations
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/// @notice Contains methods for doing math operations that revert on overflow or underflow for minimal gas cost
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library SafeMath {
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/**
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* @dev Returns the addition of two unsigned integers, reverting on
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* overflow.
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*
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* Counterpart to Solidity's `+` operator.
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*
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* Requirements:
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* - Addition cannot overflow.
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*/
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function add(uint256 a, uint256 b) internal pure returns (uint256) {
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uint256 c = a + b;
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require(c >= a, 'SafeMath: addition overflow');
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return c;
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}
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/**
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* @dev Returns the subtraction of two unsigned integers, reverting on
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* overflow (when the result is negative).
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*
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* Counterpart to Solidity's `-` operator.
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*
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* Requirements:
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* - Subtraction cannot overflow.
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*/
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function sub(uint256 a, uint256 b) internal pure returns (uint256) {
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return sub(a, b, 'SafeMath: subtraction overflow');
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}
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/**
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* @dev Returns the subtraction of two unsigned integers, reverting with custom message on
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* overflow (when the result is negative).
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*
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* Counterpart to Solidity's `-` operator.
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*
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* Requirements:
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* - Subtraction cannot overflow.
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*/
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function sub(
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uint256 a,
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uint256 b,
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string memory errorMessage
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) internal pure returns (uint256) {
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require(b <= a, errorMessage);
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uint256 c = a - b;
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return c;
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}
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/**
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* @dev Returns the multiplication of two unsigned integers, reverting on
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* overflow.
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*
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* Counterpart to Solidity's `*` operator.
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*
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* Requirements:
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* - Multiplication cannot overflow.
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*/
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function mul(uint256 a, uint256 b) internal pure returns (uint256) {
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// Gas optimization: this is cheaper than requiring 'a' not being zero, but the
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// benefit is lost if 'b' is also tested.
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// See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
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if (a == 0) {
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return 0;
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/// @notice Returns x + y, reverts if sum overflows uint256
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/// @param x The augend
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/// @param y The addend
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/// @return z The sum of x and y
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function add(uint256 x, uint256 y) internal pure returns (uint256 z) {
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require((z = x + y) >= x);
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}
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uint256 c = a * b;
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require(c / a == b, 'SafeMath: multiplication overflow');
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/// @notice Returns x - y, reverts if underflows
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/// @param x The minuend
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/// @param y The subtrahend
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/// @return z The difference of x and y
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function sub(uint256 x, uint256 y) internal pure returns (uint256 z) {
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require((z = x - y) <= x);
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}
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return c;
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}
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/// @notice Returns x - y, reverts if underflows
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/// @param x The minuend
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/// @param y The subtrahend
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/// @param message The error msg
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/// @return z The difference of x and y
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function sub(uint256 x, uint256 y, string memory message) internal pure returns (uint256 z) {
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require((z = x - y) <= x, message);
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}
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/**
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* @dev Returns the integer division of two unsigned integers. Reverts on
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* division by zero. The result is rounded towards zero.
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*
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* Counterpart to Solidity's `/` operator. Note: this function uses a
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* `revert` opcode (which leaves remaining gas untouched) while Solidity
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* uses an invalid opcode to revert (consuming all remaining gas).
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*
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* Requirements:
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* - The divisor cannot be zero.
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*/
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function div(uint256 a, uint256 b) internal pure returns (uint256) {
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return div(a, b, 'SafeMath: division by zero');
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}
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/**
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* @dev Returns the integer division of two unsigned integers. Reverts with custom message on
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* division by zero. The result is rounded towards zero.
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*
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* Counterpart to Solidity's `/` operator. Note: this function uses a
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* `revert` opcode (which leaves remaining gas untouched) while Solidity
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* uses an invalid opcode to revert (consuming all remaining gas).
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*
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* Requirements:
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* - The divisor cannot be zero.
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*/
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function div(
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uint256 a,
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uint256 b,
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string memory errorMessage
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) internal pure returns (uint256) {
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// Solidity only automatically asserts when dividing by 0
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require(b > 0, errorMessage);
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uint256 c = a / b;
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// assert(a == b * c + a % b); // There is no case in which this doesn't hold
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/// @notice Returns x * y, reverts if overflows
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/// @param x The multiplicand
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/// @param y The multiplier
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/// @return z The product of x and y
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function mul(uint256 x, uint256 y) internal pure returns (uint256 z) {
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require(x == 0 || (z = x * y) / x == y);
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}
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return c;
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}
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/// @notice Returns x / y, reverts if overflows - no specific check, solidity reverts on division by 0
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/// @param x The numerator
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/// @param y The denominator
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/// @return z The product of x and y
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function div(uint256 x, uint256 y) internal pure returns (uint256 z) {
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return x / y;
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}
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/**
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* @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
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* Reverts when dividing by zero.
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*
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* Counterpart to Solidity's `%` operator. This function uses a `revert`
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* opcode (which leaves remaining gas untouched) while Solidity uses an
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* invalid opcode to revert (consuming all remaining gas).
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*
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* Requirements:
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* - The divisor cannot be zero.
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*/
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function mod(uint256 a, uint256 b) internal pure returns (uint256) {
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return mod(a, b, 'SafeMath: modulo by zero');
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}
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/**
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* @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
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* Reverts with custom message when dividing by zero.
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*
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* Counterpart to Solidity's `%` operator. This function uses a `revert`
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* opcode (which leaves remaining gas untouched) while Solidity uses an
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* invalid opcode to revert (consuming all remaining gas).
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*
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* Requirements:
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* - The divisor cannot be zero.
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*/
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function mod(
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uint256 a,
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uint256 b,
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string memory errorMessage
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) internal pure returns (uint256) {
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require(b != 0, errorMessage);
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return a % b;
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}
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}
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}
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