// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.1.0) (utils/math/Math.sol)
pragma solidity ^0.8.20;
import {Panic} from "./Panic.sol";
import {SafeCast} from "./SafeCast.sol";
/**
* @dev Standard math utilities missing in the Solidity language.
*/
library Math {
enum Rounding {
Floor, // Toward negative infinity
Ceil, // Toward positive infinity
Trunc, // Toward zero
Expand // Away from zero
}
/**
* @dev Return the 512-bit addition of two uint256.
*
* The result is stored in two 256 variables such that sum = high * 2²⁵⁶ + low.
*/
function add512(uint256 a, uint256 b) internal pure returns (uint256 high, uint256 low) {
assembly ("memory-safe") {
low := add(a, b)
high := lt(low, a)
}
}
/**
* @dev Return the 512-bit multiplication of two uint256.
*
* The result is stored in two 256 variables such that product = high * 2²⁵⁶ + low.
*/
function mul512(uint256 a, uint256 b) internal pure returns (uint256 high, uint256 low) {
// 512-bit multiply [high low] = x * y. Compute the product mod 2²⁵⁶ and mod 2²⁵⁶ - 1, then use
// the Chinese Remainder Theorem to reconstruct the 512 bit result. The result is stored in two 256
// variables such that product = high * 2²⁵⁶ + low.
assembly ("memory-safe") {
let mm := mulmod(a, b, not(0))
low := mul(a, b)
high := sub(sub(mm, low), lt(mm, low))
}
}
/**
* @dev Returns the addition of two unsigned integers, with a success flag (no overflow).
*/
function tryAdd(uint256 a, uint256 b) internal pure returns (bool success, uint256 result) {
unchecked {
uint256 c = a + b;
success = c >= a;
result = c * SafeCast.toUint(success);
}
}
/**
* @dev Returns the subtraction of two unsigned integers, with a success flag (no overflow).
*/
function trySub(uint256 a, uint256 b) internal pure returns (bool success, uint256 result) {
unchecked {
uint256 c = a - b;
success = c <= a;
result = c * SafeCast.toUint(success);
}
}
/**
* @dev Returns the multiplication of two unsigned integers, with a success flag (no overflow).
*/
function tryMul(uint256 a, uint256 b) internal pure returns (bool success, uint256 result) {
unchecked {
uint256 c = a * b;
assembly ("memory-safe") {
// Only true when the multiplication doesn't overflow
// (c / a == b) || (a == 0)
success := or(eq(div(c, a), b), iszero(a))
}
// equivalent to: success ? c : 0
result = c * SafeCast.toUint(success);
}
}
/**
* @dev Returns the division of two unsigned integers, with a success flag (no division by zero).
*/
function tryDiv(uint256 a, uint256 b) internal pure returns (bool success, uint256 result) {
unchecked {
success = b > 0;
assembly ("memory-safe") {
// The `DIV` opcode returns zero when the denominator is 0.
result := div(a, b)
}
}
}
/**
* @dev Returns the remainder of dividing two unsigned integers, with a success flag (no division by zero).
*/
function tryMod(uint256 a, uint256 b) internal pure returns (bool success, uint256 result) {
unchecked {
success = b > 0;
assembly ("memory-safe") {
// The `MOD` opcode returns zero when the denominator is 0.
result := mod(a, b)
}
}
}
/**
* @dev Unsigned saturating addition, bounds to `2²⁵⁶ - 1` instead of overflowing.
*/
function saturatingAdd(uint256 a, uint256 b) internal pure returns (uint256) {
(bool success, uint256 result) = tryAdd(a, b);
return ternary(success, result, type(uint256).max);
}
/**
* @dev Unsigned saturating subtraction, bounds to zero instead of overflowing.
*/
function saturatingSub(uint256 a, uint256 b) internal pure returns (uint256) {
(, uint256 result) = trySub(a, b);
return result;
}
/**
* @dev Unsigned saturating multiplication, bounds to `2²⁵⁶ - 1` instead of overflowing.
*/
function saturatingMul(uint256 a, uint256 b) internal pure returns (uint256) {
(bool success, uint256 result) = tryMul(a, b);
return ternary(success, result, type(uint256).max);
}
/**
* @dev Branchless ternary evaluation for `a ? b : c`. Gas costs are constant.
*
* IMPORTANT: This function may reduce bytecode size and consume less gas when used standalone.
* However, the compiler may optimize Solidity ternary operations (i.e. `a ? b : c`) to only compute
* one branch when needed, making this function more expensive.
*/
function ternary(bool condition, uint256 a, uint256 b) internal pure returns (uint256) {
unchecked {
// branchless ternary works because:
// b ^ (a ^ b) == a
// b ^ 0 == b
return b ^ ((a ^ b) * SafeCast.toUint(condition));
}
}
/**
* @dev Returns the largest of two numbers.
*/
function max(uint256 a, uint256 b) internal pure returns (uint256) {
return ternary(a > b, a, b);
}
/**
* @dev Returns the smallest of two numbers.
*/
function min(uint256 a, uint256 b) internal pure returns (uint256) {
return ternary(a < b, a, b);
}
/**
* @dev Returns the average of two numbers. The result is rounded towards
* zero.
*/
function average(uint256 a, uint256 b) internal pure returns (uint256) {
// (a + b) / 2 can overflow.
return (a & b) + (a ^ b) / 2;
}
/**
* @dev Returns the ceiling of the division of two numbers.
*
* This differs from standard division with `/` in that it rounds towards infinity instead
* of rounding towards zero.
*/
function ceilDiv(uint256 a, uint256 b) internal pure returns (uint256) {
if (b == 0) {
// Guarantee the same behavior as in a regular Solidity division.
Panic.panic(Panic.DIVISION_BY_ZERO);
}
// The following calculation ensures accurate ceiling division without overflow.
// Since a is non-zero, (a - 1) / b will not overflow.
// The largest possible result occurs when (a - 1) / b is type(uint256).max,
// but the largest value we can obtain is type(uint256).max - 1, which happens
// when a = type(uint256).max and b = 1.
unchecked {
return SafeCast.toUint(a > 0) * ((a - 1) / b + 1);
}
}
/**
* @dev Calculates floor(x * y / denominator) with full precision. Throws if result overflows a uint256 or
* denominator == 0.
*
* Original credit to Remco Bloemen under MIT license (https://xn--2-umb.com/21/muldiv) with further edits by
* Uniswap Labs also under MIT license.
*/
function mulDiv(uint256 x, uint256 y, uint256 denominator) internal pure returns (uint256 result) {
unchecked {
(uint256 high, uint256 low) = mul512(x, y);
// Handle non-overflow cases, 256 by 256 division.
if (high == 0) {
// Solidity will revert if denominator == 0, unlike the div opcode on its own.
// The surrounding unchecked block does not change this fact.
// See https://docs.soliditylang.org/en/latest/control-structures.html#checked-or-unchecked-arithmetic.
return low / denominator;
}
// Make sure the result is less than 2²⁵⁶. Also prevents denominator == 0.
if (denominator <= high) {
Panic.panic(ternary(denominator == 0, Panic.DIVISION_BY_ZERO, Panic.UNDER_OVERFLOW));
}
///////////////////////////////////////////////
// 512 by 256 division.
///////////////////////////////////////////////
// Make division exact by subtracting the remainder from [high low].
uint256 remainder;
assembly ("memory-safe") {
// Compute remainder using mulmod.
remainder := mulmod(x, y, denominator)
// Subtract 256 bit number from 512 bit number.
high := sub(high, gt(remainder, low))
low := sub(low, remainder)
}
// Factor powers of two out of denominator and compute largest power of two divisor of denominator.
// Always >= 1. See https://cs.stackexchange.com/q/138556/92363.
uint256 twos = denominator & (0 - denominator);
assembly ("memory-safe") {
// Divide denominator by twos.
denominator := div(denominator, twos)
// Divide [high low] by twos.
low := div(low, twos)
// Flip twos such that it is 2²⁵⁶ / twos. If twos is zero, then it becomes one.
twos := add(div(sub(0, twos), twos), 1)
}
// Shift in bits from high into low.
low |= high * twos;
// Invert denominator mod 2²⁵⁶. Now that denominator is an odd number, it has an inverse modulo 2²⁵⁶ such
// that denominator * inv ≡ 1 mod 2²⁵⁶. Compute the inverse by starting with a seed that is correct for
// four bits. That is, denominator * inv ≡ 1 mod 2⁴.
uint256 inverse = (3 * denominator) ^ 2;
// Use the Newton-Raphson iteration to improve the precision. Thanks to Hensel's lifting lemma, this also
// works in modular arithmetic, doubling the correct bits in each step.
inverse *= 2 - denominator * inverse; // inverse mod 2⁸
inverse *= 2 - denominator * inverse; // inverse mod 2¹⁶
inverse *= 2 - denominator * inverse; // inverse mod 2³²
inverse *= 2 - denominator * inverse; // inverse mod 2⁶⁴
inverse *= 2 - denominator * inverse; // inverse mod 2¹²⁸
inverse *= 2 - denominator * inverse; // inverse mod 2²⁵⁶
// Because the division is now exact we can divide by multiplying with the modular inverse of denominator.
// This will give us the correct result modulo 2²⁵⁶. Since the preconditions guarantee that the outcome is
// less than 2²⁵⁶, this is the final result. We don't need to compute the high bits of the result and high
// is no longer required.
result = low * inverse;
return result;
}
}
/**
* @dev Calculates x * y / denominator with full precision, following the selected rounding direction.
*/
function mulDiv(uint256 x, uint256 y, uint256 denominator, Rounding rounding) internal pure returns (uint256) {
return mulDiv(x, y, denominator) + SafeCast.toUint(unsignedRoundsUp(rounding) && mulmod(x, y, denominator) > 0);
}
/**
* @dev Calculates floor(x * y >> n) with full precision. Throws if result overflows a uint256.
*/
function mulShr(uint256 x, uint256 y, uint8 n) internal pure returns (uint256 result) {
unchecked {
(uint256 high, uint256 low) = mul512(x, y);
if (high >= 1 << n) {
Panic.panic(Panic.UNDER_OVERFLOW);
}
return (high << (256 - n)) | (low >> n);
}
}
/**
* @dev Calculates x * y >> n with full precision, following the selected rounding direction.
*/
function mulShr(uint256 x, uint256 y, uint8 n, Rounding rounding) internal pure returns (uint256) {
return mulShr(x, y, n) + SafeCast.toUint(unsignedRoundsUp(rounding) && mulmod(x, y, 1 << n) > 0);
}
/**
* @dev Calculate the modular multiplicative inverse of a number in Z/nZ.
*
* If n is a prime, then Z/nZ is a field. In that case all elements are inversible, except 0.
* If n is not a prime, then Z/nZ is not a field, and some elements might not be inversible.
*
* If the input value is not inversible, 0 is returned.
*
* NOTE: If you know for sure that n is (big) a prime, it may be cheaper to use Fermat's little theorem and get the
* inverse using `Math.modExp(a, n - 2, n)`. See {invModPrime}.
*/
function invMod(uint256 a, uint256 n) internal pure returns (uint256) {
unchecked {
if (n == 0) return 0;
// The inverse modulo is calculated using the Extended Euclidean Algorithm (iterative version)
// Used to compute integers x and y such that: ax + ny = gcd(a, n).
// When the gcd is 1, then the inverse of a modulo n exists and it's x.
// ax + ny = 1
// ax = 1 + (-y)n
// ax ≡ 1 (mod n) # x is the inverse of a modulo n
// If the remainder is 0 the gcd is n right away.
uint256 remainder = a % n;
uint256 gcd = n;
// Therefore the initial coefficients are:
// ax + ny = gcd(a, n) = n
// 0a + 1n = n
int256 x = 0;
int256 y = 1;
while (remainder != 0) {
uint256 quotient = gcd / remainder;
(gcd, remainder) = (
// The old remainder is the next gcd to try.
remainder,
// Compute the next remainder.
// Can't overflow given that (a % gcd) * (gcd // (a % gcd)) <= gcd
// where gcd is at most n (capped to type(uint256).max)
gcd - remainder * quotient
);
(x, y) = (
// Increment the coefficient of a.
y,
// Decrement the coefficient of n.
// Can overflow, but the result is casted to uint256 so that the
// next value of y is "wrapped around" to a value between 0 and n - 1.
x - y * int256(quotient)
);
}
if (gcd != 1) return 0; // No inverse exists.
return ternary(x < 0, n - uint256(-x), uint256(x)); // Wrap the result if it's negative.
}
}
/**
* @dev Variant of {invMod}. More efficient, but only works if `p` is known to be a prime greater than `2`.
*
* From https://en.wikipedia.org/wiki/Fermat%27s_little_theorem[Fermat's little theorem], we know that if p is
* prime, then `a**(p-1) ≡ 1 mod p`. As a consequence, we have `a * a**(p-2) ≡ 1 mod p`, which means that
* `a**(p-2)` is the modular multiplicative inverse of a in Fp.
*
* NOTE: this function does NOT check that `p` is a prime greater than `2`.
*/
function invModPrime(uint256 a, uint256 p) internal view returns (uint256) {
unchecked {
return Math.modExp(a, p - 2, p);
}
}
/**
* @dev Returns the modular exponentiation of the specified base, exponent and modulus (b ** e % m)
*
* Requirements:
* - modulus can't be zero
* - underlying staticcall to precompile must succeed
*
* IMPORTANT: The result is only valid if the underlying call succeeds. When using this function, make
* sure the chain you're using it on supports the precompiled contract for modular exponentiation
* at address 0x05 as specified in https://eips.ethereum.org/EIPS/eip-198[EIP-198]. Otherwise,
* the underlying function will succeed given the lack of a revert, but the result may be incorrectly
* interpreted as 0.
*/
function modExp(uint256 b, uint256 e, uint256 m) internal view returns (uint256) {
(bool success, uint256 result) = tryModExp(b, e, m);
if (!success) {
Panic.panic(Panic.DIVISION_BY_ZERO);
}
return result;
}
/**
* @dev Returns the modular exponentiation of the specified base, exponent and modulus (b ** e % m).
* It includes a success flag indicating if the operation succeeded. Operation will be marked as failed if trying
* to operate modulo 0 or if the underlying precompile reverted.
*
* IMPORTANT: The result is only valid if the success flag is true. When using this function, make sure the chain
* you're using it on supports the precompiled contract for modular exponentiation at address 0x05 as specified in
* https://eips.ethereum.org/EIPS/eip-198[EIP-198]. Otherwise, the underlying function will succeed given the lack
* of a revert, but the result may be incorrectly interpreted as 0.
*/
function tryModExp(uint256 b, uint256 e, uint256 m) internal view returns (bool success, uint256 result) {
if (m == 0) return (false, 0);
assembly ("memory-safe") {
let ptr := mload(0x40)
// | Offset | Content | Content (Hex) |
// |-----------|------------|--------------------------------------------------------------------|
// | 0x00:0x1f | size of b | 0x0000000000000000000000000000000000000000000000000000000000000020 |
// | 0x20:0x3f | size of e | 0x0000000000000000000000000000000000000000000000000000000000000020 |
// | 0x40:0x5f | size of m | 0x0000000000000000000000000000000000000000000000000000000000000020 |
// | 0x60:0x7f | value of b | 0x<...............................b> |
// | 0x80:0x9f | value of e | 0x<...............................e> |
// | 0xa0:0xbf | value of m | 0x<...............................m> |
mstore(ptr, 0x20)
mstore(add(ptr, 0x20), 0x20)
mstore(add(ptr, 0x40), 0x20)
mstore(add(ptr, 0x60), b)
mstore(add(ptr, 0x80), e)
mstore(add(ptr, 0xa0), m)
// Given the result < m, it's guaranteed to fit in 32 bytes,
// so we can use the memory scratch space located at offset 0.
success := staticcall(gas(), 0x05, ptr, 0xc0, 0x00, 0x20)
result := mload(0x00)
}
}
/**
* @dev Variant of {modExp} that supports inputs of arbitrary length.
*/
function modExp(bytes memory b, bytes memory e, bytes memory m) internal view returns (bytes memory) {
(bool success, bytes memory result) = tryModExp(b, e, m);
if (!success) {
Panic.panic(Panic.DIVISION_BY_ZERO);
}
return result;
}
/**
* @dev Variant of {tryModExp} that supports inputs of arbitrary length.
*/
function tryModExp(
bytes memory b,
bytes memory e,
bytes memory m
) internal view returns (bool success, bytes memory result) {
if (_zeroBytes(m)) return (false, new bytes(0));
uint256 mLen = m.length;
// Encode call args in result and move the free memory pointer
result = abi.encodePacked(b.length, e.length, mLen, b, e, m);
assembly ("memory-safe") {
let dataPtr := add(result, 0x20)
// Write result on top of args to avoid allocating extra memory.
success := staticcall(gas(), 0x05, dataPtr, mload(result), dataPtr, mLen)
// Overwrite the length.
// result.length > returndatasize() is guaranteed because returndatasize() == m.length
mstore(result, mLen)
// Set the memory pointer after the returned data.
mstore(0x40, add(dataPtr, mLen))
}
}
/**
* @dev Returns whether the provided byte array is zero.
*/
function _zeroBytes(bytes memory byteArray) private pure returns (bool) {
for (uint256 i = 0; i < byteArray.length; ++i) {
if (byteArray[i] != 0) {
return false;
}
}
return true;
}
/**
* @dev Returns the square root of a number. If the number is not a perfect square, the value is rounded
* towards zero.
*
* This method is based on Newton's method for computing square roots; the algorithm is restricted to only
* using integer operations.
*/
function sqrt(uint256 a) internal pure returns (uint256) {
unchecked {
// Take care of easy edge cases when a == 0 or a == 1
if (a <= 1) {
return a;
}
// In this function, we use Newton's method to get a root of `f(x) := x² - a`. It involves building a
// sequence x_n that converges toward sqrt(a). For each iteration x_n, we also define the error between
// the current value as `ε_n = | x_n - sqrt(a) |`.
//
// For our first estimation, we consider `e` the smallest power of 2 which is bigger than the square root
// of the target. (i.e. `2**(e-1) ≤ sqrt(a) < 2**e`). We know that `e ≤ 128` because `(2¹²⁸)² = 2²⁵⁶` is
// bigger than any uint256.
//
// By noticing that
// `2**(e-1) ≤ sqrt(a) < 2**e → (2**(e-1))² ≤ a < (2**e)² → 2**(2*e-2) ≤ a < 2**(2*e)`
// we can deduce that `e - 1` is `log2(a) / 2`. We can thus compute `x_n = 2**(e-1)` using a method similar
// to the msb function.
uint256 aa = a;
uint256 xn = 1;
if (aa >= (1 << 128)) {
aa >>= 128;
xn <<= 64;
}
if (aa >= (1 << 64)) {
aa >>= 64;
xn <<= 32;
}
if (aa >= (1 << 32)) {
aa >>= 32;
xn <<= 16;
}
if (aa >= (1 << 16)) {
aa >>= 16;
xn <<= 8;
}
if (aa >= (1 << 8)) {
aa >>= 8;
xn <<= 4;
}
if (aa >= (1 << 4)) {
aa >>= 4;
xn <<= 2;
}
if (aa >= (1 << 2)) {
xn <<= 1;
}
// We now have x_n such that `x_n = 2**(e-1) ≤ sqrt(a) < 2**e = 2 * x_n`. This implies ε_n ≤ 2**(e-1).
//
// We can refine our estimation by noticing that the middle of that interval minimizes the error.
// If we move x_n to equal 2**(e-1) + 2**(e-2), then we reduce the error to ε_n ≤ 2**(e-2).
// This is going to be our x_0 (and ε_0)
xn = (3 * xn) >> 1; // ε_0 := | x_0 - sqrt(a) | ≤ 2**(e-2)
// From here, Newton's method give us:
// x_{n+1} = (x_n + a / x_n) / 2
//
// One should note that:
// x_{n+1}² - a = ((x_n + a / x_n) / 2)² - a
// = ((x_n² + a) / (2 * x_n))² - a
// = (x_n⁴ + 2 * a * x_n² + a²) / (4 * x_n²) - a
// = (x_n⁴ + 2 * a * x_n² + a² - 4 * a * x_n²) / (4 * x_n²)
// = (x_n⁴ - 2 * a * x_n² + a²) / (4 * x_n²)
// = (x_n² - a)² / (2 * x_n)²
// = ((x_n² - a) / (2 * x_n))²
// ≥ 0
// Which proves that for all n ≥ 1, sqrt(a) ≤ x_n
//
// This gives us the proof of quadratic convergence of the sequence:
// ε_{n+1} = | x_{n+1} - sqrt(a) |
// = | (x_n + a / x_n) / 2 - sqrt(a) |
// = | (x_n² + a - 2*x_n*sqrt(a)) / (2 * x_n) |
// = | (x_n - sqrt(a))² / (2 * x_n) |
// = | ε_n² / (2 * x_n) |
// = ε_n² / | (2 * x_n) |
//
// For the first iteration, we have a special case where x_0 is known:
// ε_1 = ε_0² / | (2 * x_0) |
// ≤ (2**(e-2))² / (2 * (2**(e-1) + 2**(e-2)))
// ≤ 2**(2*e-4) / (3 * 2**(e-1))
// ≤ 2**(e-3) / 3
// ≤ 2**(e-3-log2(3))
// ≤ 2**(e-4.5)
//
// For the following iterations, we use the fact that, 2**(e-1) ≤ sqrt(a) ≤ x_n:
// ε_{n+1} = ε_n² / | (2 * x_n) |
// ≤ (2**(e-k))² / (2 * 2**(e-1))
// ≤ 2**(2*e-2*k) / 2**e
// ≤ 2**(e-2*k)
xn = (xn + a / xn) >> 1; // ε_1 := | x_1 - sqrt(a) | ≤ 2**(e-4.5) -- special case, see above
xn = (xn + a / xn) >> 1; // ε_2 := | x_2 - sqrt(a) | ≤ 2**(e-9) -- general case with k = 4.5
xn = (xn + a / xn) >> 1; // ε_3 := | x_3 - sqrt(a) | ≤ 2**(e-18) -- general case with k = 9
xn = (xn + a / xn) >> 1; // ε_4 := | x_4 - sqrt(a) | ≤ 2**(e-36) -- general case with k = 18
xn = (xn + a / xn) >> 1; // ε_5 := | x_5 - sqrt(a) | ≤ 2**(e-72) -- general case with k = 36
xn = (xn + a / xn) >> 1; // ε_6 := | x_6 - sqrt(a) | ≤ 2**(e-144) -- general case with k = 72
// Because e ≤ 128 (as discussed during the first estimation phase), we know have reached a precision
// ε_6 ≤ 2**(e-144) < 1. Given we're operating on integers, then we can ensure that xn is now either
// sqrt(a) or sqrt(a) + 1.
return xn - SafeCast.toUint(xn > a / xn);
}
}
/**
* @dev Calculates sqrt(a), following the selected rounding direction.
*/
function sqrt(uint256 a, Rounding rounding) internal pure returns (uint256) {
unchecked {
uint256 result = sqrt(a);
return result + SafeCast.toUint(unsignedRoundsUp(rounding) && result * result < a);
}
}
/**
* @dev Return the log in base 2 of a positive value rounded towards zero.
* Returns 0 if given 0.
*/
function log2(uint256 x) internal pure returns (uint256 r) {
// If value has upper 128 bits set, log2 result is at least 128
r = SafeCast.toUint(x > 0xffffffffffffffffffffffffffffffff) << 7;
// If upper 64 bits of 128-bit half set, add 64 to result
r |= SafeCast.toUint((x >> r) > 0xffffffffffffffff) << 6;
// If upper 32 bits of 64-bit half set, add 32 to result
r |= SafeCast.toUint((x >> r) > 0xffffffff) << 5;
// If upper 16 bits of 32-bit half set, add 16 to result
r |= SafeCast.toUint((x >> r) > 0xffff) << 4;
// If upper 8 bits of 16-bit half set, add 8 to result
r |= SafeCast.toUint((x >> r) > 0xff) << 3;
// If upper 4 bits of 8-bit half set, add 4 to result
r |= SafeCast.toUint((x >> r) > 0xf) << 2;
// Shifts value right by the current result and use it as an index into this lookup table:
//
// | x (4 bits) | index | table[index] = MSB position |
// |------------|---------|-----------------------------|
// | 0000 | 0 | table[0] = 0 |
// | 0001 | 1 | table[1] = 0 |
// | 0010 | 2 | table[2] = 1 |
// | 0011 | 3 | table[3] = 1 |
// | 0100 | 4 | table[4] = 2 |
// | 0101 | 5 | table[5] = 2 |
// | 0110 | 6 | table[6] = 2 |
// | 0111 | 7 | table[7] = 2 |
// | 1000 | 8 | table[8] = 3 |
// | 1001 | 9 | table[9] = 3 |
// | 1010 | 10 | table[10] = 3 |
// | 1011 | 11 | table[11] = 3 |
// | 1100 | 12 | table[12] = 3 |
// | 1101 | 13 | table[13] = 3 |
// | 1110 | 14 | table[14] = 3 |
// | 1111 | 15 | table[15] = 3 |
//
// The lookup table is represented as a 32-byte value with the MSB positions for 0-15 in the last 16 bytes.
assembly ("memory-safe") {
r := or(r, byte(shr(r, x), 0x0000010102020202030303030303030300000000000000000000000000000000))
}
}
/**
* @dev Return the log in base 2, following the selected rounding direction, of a positive value.
* Returns 0 if given 0.
*/
function log2(uint256 value, Rounding rounding) internal pure returns (uint256) {
unchecked {
uint256 result = log2(value);
return result + SafeCast.toUint(unsignedRoundsUp(rounding) && 1 << result < value);
}
}
/**
* @dev Return the log in base 10 of a positive value rounded towards zero.
* Returns 0 if given 0.
*/
function log10(uint256 value) internal pure returns (uint256) {
uint256 result = 0;
unchecked {
if (value >= 10 ** 64) {
value /= 10 ** 64;
result += 64;
}
if (value >= 10 ** 32) {
value /= 10 ** 32;
result += 32;
}
if (value >= 10 ** 16) {
value /= 10 ** 16;
result += 16;
}
if (value >= 10 ** 8) {
value /= 10 ** 8;
result += 8;
}
if (value >= 10 ** 4) {
value /= 10 ** 4;
result += 4;
}
if (value >= 10 ** 2) {
value /= 10 ** 2;
result += 2;
}
if (value >= 10 ** 1) {
result += 1;
}
}
return result;
}
/**
* @dev Return the log in base 10, following the selected rounding direction, of a positive value.
* Returns 0 if given 0.
*/
function log10(uint256 value, Rounding rounding) internal pure returns (uint256) {
unchecked {
uint256 result = log10(value);
return result + SafeCast.toUint(unsignedRoundsUp(rounding) && 10 ** result < value);
}
}
/**
* @dev Return the log in base 256 of a positive value rounded towards zero.
* Returns 0 if given 0.
*
* Adding one to the result gives the number of pairs of hex symbols needed to represent `value` as a hex string.
*/
function log256(uint256 x) internal pure returns (uint256 r) {
// If value has upper 128 bits set, log2 result is at least 128
r = SafeCast.toUint(x > 0xffffffffffffffffffffffffffffffff) << 7;
// If upper 64 bits of 128-bit half set, add 64 to result
r |= SafeCast.toUint((x >> r) > 0xffffffffffffffff) << 6;
// If upper 32 bits of 64-bit half set, add 32 to result
r |= SafeCast.toUint((x >> r) > 0xffffffff) << 5;
// If upper 16 bits of 32-bit half set, add 16 to result
r |= SafeCast.toUint((x >> r) > 0xffff) << 4;
// Add 1 if upper 8 bits of 16-bit half set, and divide accumulated result by 8
return (r >> 3) | SafeCast.toUint((x >> r) > 0xff);
}
/**
* @dev Return the log in base 256, following the selected rounding direction, of a positive value.
* Returns 0 if given 0.
*/
function log256(uint256 value, Rounding rounding) internal pure returns (uint256) {
unchecked {
uint256 result = log256(value);
return result + SafeCast.toUint(unsignedRoundsUp(rounding) && 1 << (result << 3) < value);
}
}
/**
* @dev Returns whether a provided rounding mode is considered rounding up for unsigned integers.
*/
function unsignedRoundsUp(Rounding rounding) internal pure returns (bool) {
return uint8(rounding) % 2 == 1;
}
}