From f57a1c3b171fa8b95ff3148d05fdaff0f4768547 Mon Sep 17 00:00:00 2001
From: Yuri D'Elia <wavexx@thregr.org>
Date: Tue, 6 Jul 2021 00:08:55 +0200
Subject: [PATCH] CircularIndex: add static checks for index/size limits

The empty/full distinction fails to work if size matches the number of
representable positions for the index type.

Add a static check to ensure this invariant is met where possible.
---
 src/hal/circular_buffer.h | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/hal/circular_buffer.h b/src/hal/circular_buffer.h
index 89b16d8..4201a87 100644
--- a/src/hal/circular_buffer.h
+++ b/src/hal/circular_buffer.h
@@ -2,6 +2,9 @@
 
 #include <stdint.h>
 #include <stddef.h>
+#ifndef __AVR__
+    #include <limits>
+#endif
 
 /// A generic circular index class which can be used to build circular buffers
 /// Can hold up to size elements
@@ -12,6 +15,11 @@
 template <typename index_t = uint_fast8_t, size_t size = 16>
 class CircularIndex {
 public:
+#ifndef __AVR__
+    static_assert(size <= std::numeric_limits<index_t>::max(),
+        "index_t is too small for the requested size");
+#endif
+
     constexpr inline CircularIndex()
         : tail(0)
         , head(0) {}