apps/ed: add the concept of "current line"

apps/ed/glue.asm

@@ -9,5 +9,6 @@
 #include "ed/io.asm"
 .equ	BUF_RAMSTART	IO_RAMEND
 #include "ed/buf.asm"
+.equ	ED_RAMSTART	BUF_RAMEND
 #include "ed/main.asm"
 

apps/ed/main.asm

@@ -57,19 +57,27 @@
 ; stdioPutC
 ; stdioReadC
 ; unsetZ
+;
+; *** Variables ***
+;
+.equ	ED_CURLINE	ED_RAMSTART
+.equ	ED_RAMEND	ED_CURLINE+2
 
 edMain:
+	; diverge from UNIX: start at first line
+	ld	hl, 0
+	ld	(ED_CURLINE), hl
+
 	; Fill line buffer
-.loop:
+.fillLoop:
 	call	blkTell		; --> HL
 	call	blkGetC
-	jr	nz, edLoop
+	jr	nz, .mainLoop
 	call	bufAddLine
 	call	ioGetLine
-	jr	.loop
-	; Continue to loop
+	jr	.fillLoop
 
-edLoop:
+.mainLoop:
 	ld	a, ':'
 	call	stdioPutC
 .inner:
@@ -80,33 +88,82 @@ edLoop:
 	call	stdioGetLine
 	call	.processLine
 	ret	z
-	jr	edLoop
+	jr	.mainLoop
 
 ; Sets Z if we need to quit
 .processLine:
 	ld	a, (hl)
 	cp	'q'
 	ret	z
-	call	parseDecimal
+	call	edReadAddr
 	jr	z, .processNumber
-	jr	.error
+	jr	.processError
 .processNumber:
-	; number is in IX
-	; Because we don't have a line buffer yet, let's simply print seek
-	; offsets.
-	push	ix \ pop	hl
-	dec	hl		; from 1-based to zero-based
+	; number is in DE
+	; We expect HL (rest of the cmdline) to be a null char, otherwise it's
+	; garbage
+	ld	a, (hl)
+	or	a
+	jr	nz, .processError
+	ex	de, hl
+	ld	(ED_CURLINE), hl
 	call	bufGetLine
-	jr	nz, .error
+	jr	nz, .processError
 	call	printstr
 	call	printcrlf
 	; continue to end
 .processEnd:
 	call	printcrlf
 	jp	unsetZ
-.error:
+.processError:
 	ld	a, '?'
 	call	stdioPutC
 	call	printcrlf
 	jp	unsetZ
 
+; Parse the string at (HL) and sets its corresponding address in DE, properly
+; considering implicit values (current address when nothing is specified).
+; advances HL to the char next to the last parsed char.
+; Sets Z on success, unset on error. Line out of bounds isn't an error. Only
+; overflows.
+edReadAddr:
+	ld	a, (hl)
+	call	parseDecimalDigit
+	jr	c, .NaN
+
+	push	bc
+	push	ix
+	push	hl
+.loop:
+	inc	hl
+	ld	a, (hl)
+	call	parseDecimalDigit
+	jr	nc, .loop
+	; We're at the first non-digit char. Let's save it because we're going
+	; to temporarily replace it with a null.
+	ld	b, a
+	xor	a
+	ld	(hl), a
+	; Now, let's go back to the beginning of the string and parse it.
+	; but before we do this, let's save the end of string in DE
+	ex	de, hl
+	pop	hl
+	call	parseDecimal
+	; Z is set properly at this point. nothing touches Z below.
+	ld	a, b
+	ld	(de), a
+	ex	de, hl	; put end of string back from DE to HL
+	; Put addr in its final register, DE
+	push	ix \ pop de
+	dec	de	; from 1-based to 0-base. 16bit doesn't affect flags.
+	pop	ix
+	pop	bc
+	ret
+.NaN:
+	; Not a number, return current line
+	push	hl
+	ld	hl, (ED_CURLINE)
+	ex	de, hl
+	pop	hl
+	cp	a		; ensure Z
+	ret

apps/lib/parse.asm

@@ -19,10 +19,10 @@ parseDecimalDigit:
 
 ; Parse string at (HL) as a decimal value and return value in IX under the
 ; same conditions as parseLiteral.
+; Sets Z on success, unset on error.
 parseDecimal:
 	push	hl
 	push	de
-	push	bc
 
 	ld	ix, 0
 .loop:
@@ -52,10 +52,11 @@ parseDecimal:
 	inc	hl
 	jr	.loop
 
+	cp	a	; ensure Z
+	jr	.end
 .error:
 	call	unsetZ
 .end:
-	pop	bc
 	pop	de
 	pop	hl
 	ret

kernel/stdio.asm

@@ -160,6 +160,15 @@ stdioReadC:
 
 .complete:
 	; The line in our buffer is complete.
+	; But before we do that, let's take care of a special case: the empty
+	; line. If we didn't add any character since the last "complete", then
+	; our buffer's content is the content from the last time. Let's set this
+	; to an empty string.
+	ld	a, (STDIO_BUFIDX)
+	or	a
+	jr	nz, .completeSkip
+	ld	(STDIO_BUF), a
+.completeSkip:
 	xor	a		; sets Z
 	ld	(STDIO_BUFIDX), a
 	ret