avr: added RingBufferY_PeekByte

avr/common/ringbuffer_y.asm

@@ -52,9 +52,9 @@ RingBufferY_WriteByte:
 
 
 ; ---------------------------------------------------------------------------
-; @macro m_ringbuffer_y_readbyte
+; @routine RingBufferY_ReadByte
 ;
-; @param Y   base address of ringbuffer struct
+; @param  Y     base address of ringbuffer struct
 ; @return CFLAG set if okay, cleared on error (i.e. buffer empty)
 ; @return R16 byte read
 ; @clobbers R17, R18, X
@@ -71,6 +71,31 @@ RingBufferY_ReadByte:
 
 
 
+; ---------------------------------------------------------------------------
+; @routine RingBufferY_PeekByte
+;
+; @param Y   base address (for "LDD Y+nn" and "STD Y+nn")
+; @param %0 offset to Y to access maxBytes variable (for "LDD Y+nn" and "STD Y+nn")
+; @param %1 offset to Y to access usedBytes
+; @param %2 offset to Y to access readPos variable
+; @param %3 offset to Y to access writePos variable
+; @param %4 offset to Y to access buffer
+; @return CFLAG set if okay, cleared on error (i.e. buffer empty)
+; @return R16 byte read
+; @clobbers R17, R18, X
+
+RingBufferY_PeekByte:
+  m_ringbuffer_y_peekbyte \
+    RINGBUFFERY_OFFS_MAXSIZE, \
+    RINGBUFFERY_OFFS_USED, \
+    RINGBUFFERY_OFFS_READPOS, \
+    RINGBUFFERY_OFFS_WRITEPOS, \
+    RINGBUFFERY_OFFS_DATA
+  ret
+; @end
+
+
+
 ; ---------------------------------------------------------------------------
 ; @macro m_ringbuffer_y_reset
 ;