archive: freeze IR-protocol WIP before stepwise integration

IrInterruptGuard.h

@@ -0,0 +1,51 @@
+#pragma once
+
+#include <Arduino.h>
+
+#if defined(__AVR__)
+#include <avr/interrupt.h>
+#include <avr/io.h>
+#endif
+
+/**
+ * Nest-safe interrupt guard for the short ISR/main shared-state sections used
+ * by IR-protocol.  Unlike a noInterrupts()/interrupts() pair it restores the
+ * previous state and therefore never enables interrupts from inside an ISR.
+ */
+class IrInterruptGuard final
+{
+public:
+    IrInterruptGuard()
+    {
+#if defined(__arm__) || defined(__thumb__) || defined(ARDUINO_ARCH_STM32)
+        state_ = __get_PRIMASK();
+        __disable_irq();
+#elif defined(__AVR__)
+        state_ = SREG;
+        cli();
+#else
+        noInterrupts();
+#endif
+    }
+
+    ~IrInterruptGuard()
+    {
+#if defined(__arm__) || defined(__thumb__) || defined(ARDUINO_ARCH_STM32)
+        if ((state_ & 1U) == 0U)
+            __enable_irq();
+#elif defined(__AVR__)
+        SREG = static_cast<uint8_t>(state_);
+#else
+        interrupts();
+#endif
+    }
+
+    IrInterruptGuard(const IrInterruptGuard&) = delete;
+    IrInterruptGuard& operator=(const IrInterruptGuard&) = delete;
+
+private:
+#if defined(__arm__) || defined(__thumb__) || defined(ARDUINO_ARCH_STM32) || \
+    defined(__AVR__)
+    uint32_t state_ = 0U;
+#endif
+};