From 2e126cb99fa94c842dc08b409047dc5eda64704c Mon Sep 17 00:00:00 2001
From: Pavel Nadein <pavel.nadein@cpp.canon>
Date: Mon, 22 Aug 2022 11:22:22 +0200
Subject: [PATCH] [SPSCQueue] limit the idx value

When the reader/writed index pointer is increased, limit the value to
the maximum queue size making a queue circular.

Signed-off-by: Pavel Nadein <pavel.nadein@cpp.canon>
---
 SPSCQueue.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/SPSCQueue.h b/SPSCQueue.h
index 2c700db..2eeab36 100644
--- a/SPSCQueue.h
+++ b/SPSCQueue.h
@@ -42,7 +42,7 @@ class SPSCQueue
     }
 
     void push() {
-      ((std::atomic<uint32_t>*)&write_idx)->store(write_idx + 1, std::memory_order_release);
+      ((std::atomic<uint32_t>*)&write_idx)->store((write_idx + 1) % CNT, std::memory_order_release);
     }
 
     template<typename Writer>
@@ -68,7 +68,7 @@ class SPSCQueue
     }
 
     void pop() {
-      ((std::atomic<uint32_t>*)&read_idx)->store(read_idx + 1, std::memory_order_release);
+      ((std::atomic<uint32_t>*)&read_idx)->store((read_idx + 1) % CNT, std::memory_order_release);
     }
 
     template<typename Reader>