Implement line reading in calculator.asm

calculator.asm

@@ -1,21 +1,143 @@
 org 0
 
 start:
-	load r0, lit01
-	load r1, litff
-	cleq r0, r0, pushWord
-	cleq r0, r0, stPrinthex
-
-	xor r0, r0
-	load r1, lit41
-	cleq r0, r0, pushWord
-	cleq r0, r0, stPrinthex
-
-	cleq r0, r0, stSub
-	cleq r0, r0, stPrinthex
+	cleq r0, r0, stReadline
+	cleq r0, r0, dumpstack
 
 	halt
 
+dumpstack:
+	load r0, SPStart+0
+	load r1, SPStart+1
+	store dumpstackPtr+0, r0
+	store dumpstackPtr+1, r1
+
+	dumpstackLoop:
+		load r0, dumpstackPtr+0
+		load r1, dumpstackPtr+1
+		load r2, SP+0
+		load r3, SP+1
+
+		brneq r0, r2, dumpstackDumpword
+		breq r1, r3, dumpstackEnd
+
+		dumpstackDumpword:
+		load r0, dumpstackPtr+0
+		load r1, dumpstackPtr+1
+		store loadByteHigh, r0
+		store loadByteLow, r1
+		cleq r0, r0, loadByte
+		cleq r0, r0, writehexByte
+
+		load r0, dumpstackPtr+0
+		load r1, dumpstackPtr+1
+		cleq r0, r0, incWord
+		store dumpstackPtr+0, r0
+		store dumpstackPtr+1, r1
+
+		load r0, dumpstackPtr+0
+		load r1, dumpstackPtr+1
+		store loadByteHigh, r0
+		store loadByteLow, r1
+		cleq r0, r0, loadByte
+		cleq r0, r0, writehexByte
+
+		load r0, dumpstackPtr+0
+		load r1, dumpstackPtr+1
+		cleq r0, r0, incWord
+		store dumpstackPtr+0, r0
+		store dumpstackPtr+1, r1
+
+		load r0, litcharSpace
+		store ffff, r0
+
+		breq r0, r0, dumpstackLoop
+
+	dumpstackEnd:
+		breq r0, r0, newline
+
+	dumpstackPtr: addr dumpstackPtr
+
+stReadline:
+	; Current index starts at 0
+	xor r0, r0
+	xor r1, r1
+	cleq r0, r0, pushWord
+
+	readlineLoop:
+		; Read a byte of input
+		cleq r0, r0, stKey
+
+		; Is it enter?
+		cleq r0, r0, peekWord
+		load r0, litcharCR
+		breq r0, r1, readlineEnter
+
+		; Is it backspace?
+		load r0, litcharBS
+		breq r0, r1, readlineBackspace
+
+		; Is the buffer full?
+		cleq r0, r0, stOver
+		load r0, linebufSize+0
+		load r1, linebufSize+1
+		cleq r0, r0, pushWord
+		cleq r0, r0, stGtEq
+		brneq r0, r1, readlineBufFull
+
+		; Calculate address
+		cleq r0, r0, stOver
+		load r0, linebufStart+0
+		load r1, linebufStart+1
+		cleq r0, r0, pushWord
+		cleq r0, r0, stAdd
+
+		; Store the read byte
+		cleq r0, r0, stStoreByte
+
+		; Increase index
+		cleq r0, r0, stInc
+
+		breq r0, r0, readlineLoop
+
+	readlineEnter:
+		; Remove the CR byte off the stack, as we only want to return the length
+		cleq r0, r0, popWord
+		breq r0, r0, newline
+
+	readlineBackspace:
+		; Remove the BS byte off the stack
+		cleq r0, r0, popWord
+
+		; Are we at the beginning of the line?
+		cleq r0, r0, stDup
+		xor r0, r0
+		xor r1, r1
+		cleq r0, r0, pushWord
+		cleq r0, r0, stSwap
+		cleq r0, r0, stGtEq
+		brneq r0, r1, readlineLoop
+
+		; Decrease the index and erase the echoed character
+		cleq r0, r0, stDec
+		load r3, litcharSpace
+		store ffff, r3
+		load r3, litcharBS
+		store ffff, r3
+
+		breq r0, r0, readlineLoop
+
+	readlineBufFull:
+		; Drop the input byte and erase the echoed character
+		cleq r0, r0, popWord
+		load r3, litcharBS
+		store ffff, r3
+		load r3, litcharSpace
+		store ffff, r3
+		load r3, litcharBS
+		store ffff, r3
+		breq r0, r0, readlineLoop
+
 ; ==================================================================
 ; Stack-based functions
 ; ==================================================================
@@ -42,6 +164,18 @@ stSub:
 	cleq r0, r0, subWord
 	breq r0, r0, pushWord
 
+; a -- a+1
+stInc:
+	cleq r0, r0, popWord
+	cleq r0, r0, incWord
+	breq r0, r0, pushWord
+
+; a -- a-1
+stDec:
+	cleq r0, r0, popWord
+	cleq r0, r0, decWord
+	breq r0, r0, pushWord
+
 ; a b --
 ; if a >= b then r0:r1 = 0001
 ; else r0:r1 = 0000
@@ -62,7 +196,7 @@ stGtEq:
 
 ; n -- n
 stPrinthex:
-	cleq r0, r0, peekWord
+	cleq r0, r0, popWord
 	cleq r0, r0, writehexWord
 	breq r0, r0, newline
 
@@ -78,6 +212,51 @@ stEmit:
 	store ffff, r1
 	ret
 
+; ------------------------------------------------------------------
+; Stack manipulation
+; ------------------------------------------------------------------
+
+; a - a a
+stDup:
+	cleq r0, r0, peekWord
+	breq r0, r0, pushWord
+
+; a b -- a b a
+stOver:
+	cleq r0, r0, popWord
+	cleq r0, r0, tmpStoreWord01
+	cleq r0, r0, peekWord
+	cleq r0, r0, tmp2StoreWord01
+	cleq r0, r0, tmpLoadWord01
+	cleq r0, r0, pushWord
+	cleq r0, r0, tmp2LoadWord01
+	breq r0, r0, pushWord
+
+; a b -- b a
+stSwap:
+	cleq r0, r0, popWord
+	cleq r0, r0, tmpStoreWord01
+	cleq r0, r0, popWord
+	cleq r0, r0, tmp2StoreWord01
+	cleq r0, r0, tmpLoadWord01
+	cleq r0, r0, pushWord
+	cleq r0, r0, tmp2LoadWord01
+	breq r0, r0, pushWord
+
+; ------------------------------------------------------------------
+; Memory
+; ------------------------------------------------------------------
+
+; a p --
+stStoreByte:
+	cleq r0, r0, popWord
+	store storeByteHigh, r0
+	store storeByteLow, r1
+	cleq r0, r0, popWord
+	xor r0, r0
+	or r0, r1
+	breq r0, r0, storeByte
+
 ; ==================================================================
 ; Low-level functions
 ; ==================================================================
@@ -88,16 +267,8 @@ stEmit:
 
 tmpWordHigh: data 0
 tmpWordLow: data 0
-
-; out:
-;  r0:r1 = word
-; clobbers:
-;  r2, r3
-peekWord:
-	cleq r0, r0, popWord
-	cleq r0, r0, tmpStoreWord01
-	cleq r0, r0, pushWord
-	breq r0, r0, tmpLoadWord01
+tmpWord2High: data 0
+tmpWord2Low: data 0
 
 ; in:
 ;  r0:r1 = word
@@ -120,6 +291,36 @@ tmpLoadWord23:
 	load r3, tmpWordLow
 	ret
 
+; in:
+;  r0:r1 = word
+tmp2StoreWord01:
+	store tmpWord2High, r0
+	store tmpWord2Low, r1
+	ret
+
+; out:
+;  r0:r1 = word
+tmp2LoadWord01:
+	load r0, tmpWord2High
+	load r1, tmpWord2Low
+	ret
+
+; out:
+;  r0:r1 = word
+; clobbers:
+;  r2, r2
+peekWord:
+	cleq r0, r0, popWord
+	store peekWordHigh, r0
+	store peekWordLow, r1
+	cleq r0, r0, pushWord
+	load r0, peekWordHigh
+	load r1, peekWordLow
+	ret
+
+	peekWordHigh: data 0
+	peekWordLow: data 0
+
 ; in:
 ;  r0:r1 = word
 ; clobbers:
@@ -685,6 +886,9 @@ lit0d: data 0d
 lit0e: data 0e
 lit0f: data 0f
 
+litcharSpace:
+lit20: data 20
+
 litchar0:
 lit30: data 30
 litchar1:
@@ -741,8 +945,14 @@ lit72: data 72
 litff: data ff
 
 ; ==================================================================
-; Stack
+; Data
 ; ==================================================================
 
-SP: addr stackBase
-stackBase:
+linebufStart: addr end
+linebufSize:
+	data 00
+	data 80
+SP: addr end + 80
+SPStart: addr end + 80
+
+end: