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| author | bunnei <bunneidev@gmail.com> | 2021-02-19 18:04:23 -0800 |
|---|---|---|
| committer | bunnei <bunneidev@gmail.com> | 2021-02-19 18:04:23 -0800 |
| commit | 3acb265c9ee8ac26ab43361997a5db0e4b9fa47c (patch) | |
| tree | a694010851607ea3aa341a7879db121236867bc7 /src/common/uint128.h | |
| parent | 728ee181ebdabf61ef7d4d9bd688cdfde4a9eaff (diff) | |
common: wall_clock: Fix integer overflow with StandardWallClock.
- Previous optimized impl. resulted in an integer overflow, so revert.
- This is our slow/fallback path that should never be really be used, so the optimization in unimportant.
Diffstat (limited to 'src/common/uint128.h')
| -rw-r--r-- | src/common/uint128.h | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/src/common/uint128.h b/src/common/uint128.h index 83560a9cee..4780b2f9d3 100644 --- a/src/common/uint128.h +++ b/src/common/uint128.h @@ -98,4 +98,24 @@ namespace Common { #endif } +// This function divides a u128 by a u32 value and produces two u64 values: +// the result of division and the remainder +[[nodiscard]] static inline std::pair<u64, u64> Divide128On32(u128 dividend, u32 divisor) { + u64 remainder = dividend[0] % divisor; + u64 accum = dividend[0] / divisor; + if (dividend[1] == 0) + return {accum, remainder}; + // We ignore dividend[1] / divisor as that overflows + const u64 first_segment = (dividend[1] % divisor) << 32; + accum += (first_segment / divisor) << 32; + const u64 second_segment = (first_segment % divisor) << 32; + accum += (second_segment / divisor); + remainder += second_segment % divisor; + if (remainder >= divisor) { + accum++; + remainder -= divisor; + } + return {accum, remainder}; +} + } // namespace Common |