machine: update ringbuffer to use runtime/volatile.Register8

This avoids the //go:volatile pragma, which will be removed soon.
There were no changes to the output of the smoke tests.

src/machine/buffer.go

@@ -1,9 +1,10 @@
 package machine
 
-const bufferSize = 128
+import (
+	"runtime/volatile"
+)
 
-//go:volatile
-type volatileByte byte
+const bufferSize = 128
 
 // RingBuffer is ring buffer implementation inspired by post at
 // https://www.embeddedrelated.com/showthread/comp.arch.embedded/77084-1.php
@@ -12,9 +13,9 @@ type volatileByte byte
 // members of a struct are not compiled correctly by TinyGo.
 // See https://github.com/tinygo-org/tinygo/issues/151 for details.
 type RingBuffer struct {
-	rxbuffer [bufferSize]volatileByte
-	head     volatileByte
-	tail     volatileByte
+	rxbuffer [bufferSize]volatile.Register8
+	head     volatile.Register8
+	tail     volatile.Register8
 }
 
 // NewRingBuffer returns a new ring buffer.
@@ -24,15 +25,15 @@ func NewRingBuffer() *RingBuffer {
 
 // Used returns how many bytes in buffer have been used.
 func (rb *RingBuffer) Used() uint8 {
-	return uint8(rb.head - rb.tail)
+	return uint8(rb.head.Get() - rb.tail.Get())
 }
 
 // Put stores a byte in the buffer. If the buffer is already
 // full, the method will return false.
 func (rb *RingBuffer) Put(val byte) bool {
 	if rb.Used() != bufferSize {
-		rb.head++
-		rb.rxbuffer[rb.head%bufferSize] = volatileByte(val)
+		rb.head.Set(rb.head.Get() + 1)
+		rb.rxbuffer[rb.head.Get()%bufferSize].Set(val)
 		return true
 	}
 	return false
@@ -42,8 +43,8 @@ func (rb *RingBuffer) Put(val byte) bool {
 // the method will return a false as the second value.
 func (rb *RingBuffer) Get() (byte, bool) {
 	if rb.Used() != 0 {
-		rb.tail++
-		return byte(rb.rxbuffer[rb.tail%bufferSize]), true
+		rb.tail.Set(rb.tail.Get() + 1)
+		return rb.rxbuffer[rb.tail.Get()%bufferSize].Get(), true
 	}
 	return 0, false
 }