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Small loop refactor to make Slither happier #90

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merged 2 commits into from
Aug 24, 2020
Merged

Small loop refactor to make Slither happier #90

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d7025e2
Refactored the loop in RNG.bitsRequired
pdyraga Aug 21, 2020
5588f31
Initialize the index in RNG.getIndex function
pdyraga Aug 21, 2020
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30 changes: 15 additions & 15 deletions contracts/RNG.sol
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Original file line number Diff line number Diff line change
Expand Up @@ -135,22 +135,22 @@ library RNG {
/// @return uint The smallest number of bits
/// that can contain the number `range-1`.
function bitsRequired(uint256 range) internal pure returns (uint256) {
uint256 bits;
// Start at 19 to be faster for large ranges
for (bits = (POSITION_BITS - 1); bits >= 0; bits--) {
// Left shift by `bits`,
// so we have a 1 in the (bits + 1)th least significant bit
// and 0 in other bits.
// If this number is equal or greater than `range`,
// the range [0, range-1] fits in `bits` bits.
//
// Because we loop from high bits to low bits,
// we find the highest number of bits that doesn't fit the range,
// and return that number + 1.
if (1 << bits < range) {
break;
}
uint256 bits = POSITION_BITS - 1;

// Left shift by `bits`,
// so we have a 1 in the (bits + 1)th least significant bit
// and 0 in other bits.
// If this number is equal or greater than `range`,
// the range [0, range-1] fits in `bits` bits.
//
// Because we loop from high bits to low bits,
// we find the highest number of bits that doesn't fit the range,
// and return that number + 1.
while (1 << bits >= range) {
bits--;
}

return bits + 1;
}

Expand Down Expand Up @@ -197,7 +197,7 @@ library RNG {
{
uint256 bits = bitsRequired(range);
bool found = false;
uint256 index;
uint256 index = 0;
bytes32 newState = state;
while (!found) {
index = truncate(bits, uint256(newState));
Expand Down