From dfaedb450b4eb4c8b6165da9383771f801cb8609 Mon Sep 17 00:00:00 2001
From: SASANO Takayoshi <uaa@uaa.org.uk>
Date: Thu, 2 Jul 2020 06:40:26 +0900
Subject: [PATCH] replace rand() -> MT19937 random number generator

sometimes rand() makes problem so replace it to MT19937 in C++11 <random>.
---
 DMRNetwork.cpp   | 18 +++++++++++-------
 DMRNetwork.h     |  2 ++
 DStarNetwork.cpp | 11 +++++++----
 DStarNetwork.h   |  2 ++
 4 files changed, 22 insertions(+), 11 deletions(-)

diff --git a/DMRNetwork.cpp b/DMRNetwork.cpp
index b2aedb5..fece49c 100644
--- a/DMRNetwork.cpp
+++ b/DMRNetwork.cpp
@@ -66,7 +66,8 @@ m_height(0),
 m_location(),
 m_description(),
 m_url(),
-m_beacon(false)
+m_beacon(false),
+m_random()
 {
 	assert(!address.empty());
 	assert(port > 0U);
@@ -85,11 +86,13 @@ m_beacon(false)
 	m_id[2U] = id >> 8;
 	m_id[3U] = id >> 0;
 
-	CStopWatch stopWatch;
-	::srand(stopWatch.start());
+	std::random_device rd;
+	std::mt19937 mt(rd());
+	m_random = mt;
 
-	m_streamId[0U] = ::rand() + 1U;
-	m_streamId[1U] = ::rand() + 1U;
+	std::uniform_int_distribution<uint32_t> dist(0x00000001, 0xfffffffe);
+	m_streamId[0U] = dist(m_random);
+	m_streamId[1U] = dist(m_random);
 }
 
 CDMRNetwork::~CDMRNetwork()
@@ -246,6 +249,7 @@ bool CDMRNetwork::write(const CDMRData& data)
 
 	unsigned int slotIndex = slotNo - 1U;
 
+	std::uniform_int_distribution<uint32_t> dist(0x00000001, 0xfffffffe);
 	unsigned char dataType = data.getDataType();
 	if (dataType == DT_VOICE_SYNC) {
 		buffer[15U] |= 0x10U;
@@ -253,10 +257,10 @@ bool CDMRNetwork::write(const CDMRData& data)
 		buffer[15U] |= data.getN();
 	} else {
 		if (dataType == DT_VOICE_LC_HEADER)
-			m_streamId[slotIndex] = ::rand() + 1U;
+			m_streamId[slotIndex] = dist(m_random);
 
 		if (dataType == DT_CSBK || dataType == DT_DATA_HEADER)
-			m_streamId[slotIndex] = ::rand() + 1U;
+			m_streamId[slotIndex] = dist(m_random);
 
 		buffer[15U] |= (0x20U | dataType);
 	}
diff --git a/DMRNetwork.h b/DMRNetwork.h
index 9d1c52e..754c970 100644
--- a/DMRNetwork.h
+++ b/DMRNetwork.h
@@ -27,6 +27,7 @@
 
 #include <string>
 #include <cstdint>
+#include <random>
 
 class CDMRNetwork
 {
@@ -106,6 +107,7 @@ private:
 	std::string    m_url;
 
 	bool           m_beacon;
+	std::mt19937   m_random;
 
 	bool writeLogin();
 	bool writeAuthorisation();
diff --git a/DStarNetwork.cpp b/DStarNetwork.cpp
index de0af69..d13d773 100644
--- a/DStarNetwork.cpp
+++ b/DStarNetwork.cpp
@@ -44,14 +44,16 @@ m_inId(0U),
 m_buffer(1000U, "D-Star Network"),
 m_pollTimer(1000U, 60U),
 m_linkStatus(LS_NONE),
-m_linkReflector(NULL)
+m_linkReflector(NULL),
+m_random()
 {
 	m_address = CUDPSocket::lookup(gatewayAddress);
 
 	m_linkReflector = new unsigned char[DSTAR_LONG_CALLSIGN_LENGTH];
 
-	CStopWatch stopWatch;
-	::srand(stopWatch.start());
+	std::random_device rd;
+	std::mt19937 mt(rd());
+	m_random = mt;
 }
 
 CDStarNetwork::~CDStarNetwork()
@@ -85,7 +87,8 @@ bool CDStarNetwork::writeHeader(const unsigned char* header, unsigned int length
 	buffer[4] = busy ? 0x22U : 0x20U;
 
 	// Create a random id for this transmission
-	m_outId = (::rand() % 65535U) + 1U;
+	std::uniform_int_distribution<uint16_t> dist(0x0001, 0xfffe);
+	m_outId = dist(m_random);
 
 	buffer[5] = m_outId / 256U;	// Unique session id
 	buffer[6] = m_outId % 256U;
diff --git a/DStarNetwork.h b/DStarNetwork.h
index aeebbbf..991c031 100644
--- a/DStarNetwork.h
+++ b/DStarNetwork.h
@@ -26,6 +26,7 @@
 
 #include <cstdint>
 #include <string>
+#include <random>
 
 class CDStarNetwork {
 public:
@@ -64,6 +65,7 @@ private:
 	CTimer         m_pollTimer;
 	LINK_STATUS    m_linkStatus;
 	unsigned char* m_linkReflector;
+	std::mt19937   m_random;
 
 	bool writePoll(const char* text);
 };