From 9e64d69bf74c8a381fb59841519cc3736bce14d4 Mon Sep 17 00:00:00 2001
From: John Newbery <john@johnnewbery.com>
Date: Tue, 14 Dec 2021 10:15:10 +0000
Subject: [move] Move PoissonNextSend to src/random and update comment

PoissonNextSend is used by net and net_processing and is stateless, so
place it in the utility random.cpp translation unit.
---
 src/random.cpp | 7 +++++++
 1 file changed, 7 insertions(+)

(limited to 'src/random.cpp')

diff --git a/src/random.cpp b/src/random.cpp
index 6eb06c5d47..919061e61d 100644
--- a/src/random.cpp
+++ b/src/random.cpp
@@ -19,6 +19,7 @@
 #include <sync.h>     // for Mutex
 #include <util/time.h> // for GetTimeMicros()
 
+#include <cmath>
 #include <stdlib.h>
 #include <thread>
 
@@ -714,3 +715,9 @@ void RandomInit()
 
     ReportHardwareRand();
 }
+
+std::chrono::microseconds PoissonNextSend(std::chrono::microseconds now, std::chrono::seconds average_interval)
+{
+    double unscaled = -log1p(GetRand(1ULL << 48) * -0.0000000000000035527136788 /* -1/2^48 */);
+    return now + std::chrono::duration_cast<std::chrono::microseconds>(unscaled * average_interval + 0.5us);
+}
-- 
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