Merge #20602: util: Allow use of C++14 chrono literals

fa11110bff6288f63e0c487e2e4b4079fb0f4569 util: Allow use of C++14 chrono literals (MarcoFalke)

Pull request description:

  I think we should allow the use of chrono literals for new code to make it less verbose. Obviously old code can stay as-is.

  This patch pulls in the needed namespace and replaces some lines for illustrative purposes.

ACKs for top commit:
  vasild:
    ACK fa11110bff6288f63e0c487e2e4b4079fb0f4569
  jonatack:
    ACK fa11110bff6288f63e0c487e2e4b4079fb0f4569

Tree-SHA512: ee2b72c8f28dee07b33b9a8ee8f7c87c0bc43b05c56a17b786cf9803ef204c7628e01b02de1af1a4eb01f5cdf6fc336f69c2833e17acd606ebda20ac6917e6bb

src/net.h

@@ -1016,7 +1016,7 @@ public:
         // Used for BIP35 mempool sending
         bool fSendMempool GUARDED_BY(cs_tx_inventory){false};
         // Last time a "MEMPOOL" request was serviced.
-        std::atomic<std::chrono::seconds> m_last_mempool_req{std::chrono::seconds{0}};
+        std::atomic<std::chrono::seconds> m_last_mempool_req{0s};
         std::chrono::microseconds nNextInvSend{0};
 
         RecursiveMutex cs_feeFilter;
@@ -1049,7 +1049,7 @@ public:
     // The pong reply we're expecting, or 0 if no pong expected.
     std::atomic<uint64_t> nPingNonceSent{0};
     /** When the last ping was sent, or 0 if no ping was ever sent */
-    std::atomic<std::chrono::microseconds> m_ping_start{std::chrono::microseconds{0}};
+    std::atomic<std::chrono::microseconds> m_ping_start{0us};
     // Last measured round-trip time.
     std::atomic<int64_t> nPingUsecTime{0};
     // Best measured round-trip time.

src/net_processing.cpp

@@ -4057,7 +4057,7 @@ bool PeerManager::SendMessages(CNode* pto)
             // over since our last self-announcement, but there is only a small
             // bandwidth cost that we can incur by doing this (which happens
             // once a day on average).
-            if (pto->m_next_local_addr_send != std::chrono::microseconds::zero()) {
+            if (pto->m_next_local_addr_send != 0us) {
                 pto->m_addr_known->reset();
             }
             AdvertiseLocal(pto);

src/randomenv.cpp

@@ -69,7 +69,7 @@ void RandAddSeedPerfmon(CSHA512& hasher)
 
     // 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}};
+    static std::atomic<std::chrono::seconds> last_perfmon{0s};
     auto last_time = last_perfmon.load();
     auto current_time = GetTime<std::chrono::seconds>();
     if (current_time < last_time + std::chrono::minutes{10}) return;

src/util/time.h

@@ -6,9 +6,11 @@
 #ifndef BITCOIN_UTIL_TIME_H
 #define BITCOIN_UTIL_TIME_H
 
+#include <chrono>
 #include <stdint.h>
 #include <string>
-#include <chrono>
+
+using namespace std::chrono_literals;
 
 void UninterruptibleSleep(const std::chrono::microseconds& n);