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[core] Derive fast_div1000_32 constants from expressions

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J. Nick Koston
2026-03-01 23:21:08 -10:00
parent 4dbc139ede
commit 17a10bf303
1 changed files with 3 additions and 3 deletions
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esphome/core/helpers.h
+3 -3
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@@ -546,9 +546,9 @@ inline uint32_t fnv1a_hash(const std::string &str) { return fnv1a_hash(str.c_str
/// See: https://en.wikipedia.org/wiki/Euclidean_division
/// See: https://ridiculousfish.com/blog/posts/labor-of-division-episode-iii.html
inline ESPHOME_ALWAYS_INLINE uint32_t fast_div1000_32(uint64_t us) {
static constexpr uint32_t D = 1000U; // divisor (microseconds per millisecond)
static constexpr uint32_t Q = 4294967U; // 2^32 / 1000
static constexpr uint32_t R = 296U; // 2^32 % 1000
static constexpr uint32_t D = 1000U;
static constexpr uint32_t Q = static_cast<uint32_t>((1ULL << 32) / D); // 4294967
static constexpr uint32_t R = static_cast<uint32_t>((1ULL << 32) % D); // 296
uint32_t lo = static_cast<uint32_t>(us);
uint32_t hi = static_cast<uint32_t>(us >> 32);
// Combine remainder term: hi * (2^32 % 1000) + lo