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random: fixes read buffer resizing in RandAddSeedPerfmon

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+ Replaces std::max with std::min to resize buffer in RandAddSeedPerfmon
+ Documents behavior of RandAddSeedPerfmon
This commit is contained in:
Ethan Heilman 2020-10-04 21:07:51 -04:00
parent cce1513179
commit bd5215103e
1 changed files with 3 additions and 2 deletions
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5
src/randomenv.cpp
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@ -67,7 +67,8 @@ void RandAddSeedPerfmon(CSHA512& hasher)
#ifdef WIN32
// Seed with the entire set of perfmon data
// This can take up to 2 seconds, so only do it every 10 minutes
// This can take up to 2 seconds, so only do it every 10 minutes.
// Initialize last_perfmon to 0 seconds, we don't skip the first call.
static std::atomic<std::chrono::seconds> last_perfmon{std::chrono::seconds{0}};
auto last_time = last_perfmon.load();
auto current_time = GetTime<std::chrono::seconds>();
@ -83,7 +84,7 @@ void RandAddSeedPerfmon(CSHA512& hasher)
ret = RegQueryValueExA(HKEY_PERFORMANCE_DATA, "Global", nullptr, nullptr, vData.data(), &nSize);
if (ret != ERROR_MORE_DATA || vData.size() >= nMaxSize)
break;
vData.resize(std::max((vData.size() * 3) / 2, nMaxSize)); // Grow size of buffer exponentially
vData.resize(std::min((vData.size() * 3) / 2, nMaxSize)); // Grow size of buffer exponentially
}
RegCloseKey(HKEY_PERFORMANCE_DATA);
if (ret == ERROR_SUCCESS) {