From 8a4f4928e5b9c6eec5ccee8574d9dc2f0b948d74 Mon Sep 17 00:00:00 2001
From: Paul Gardner-Stephen <paul@servalproject.org>
Date: Sat, 20 Apr 2019 02:06:31 +0930
Subject: [PATCH] begin implementing chrin to read from keyboard buffer

---
 c64/kernal/chrin.s | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/c64/kernal/chrin.s b/c64/kernal/chrin.s
index 44999288..3d48373b 100644
--- a/c64/kernal/chrin.s
+++ b/c64/kernal/chrin.s
@@ -5,8 +5,27 @@
 	;; Repeated calls after that read out the successive bytes of the line of input.
 chrin:
 	;; XXX - Not yet implemented, so infinite loop for now
-	inc $d020
-	jmp chrin
+	lda keys_in_key_buffer
+	beq chrin
+
+	;; Print character
+	lda keyboard_buffer
+	jsr chrout
+
+	;; Pop key out of keyboard buffer
+	;; Disable interrupts while reading from keyboard buffer
+	;; so that no race conditions can occur
+	sei
+	ldx #$00
+	ldy #$01
+*	lda keyboard_buffer,y
+	sta keyboard_buffer,x
+	inx
+	iny
+	cpy keys_in_key_buffer
+	bne -
+	dec keys_in_key_buffer
+	cli
 	
 	lda #$00
 	clc