From ad7428e471bfff1b81742dda3eb86ccb544b41fd Mon Sep 17 00:00:00 2001
From: Virgil Dupras <hsoft@hardcoded.net>
Date: Fri, 17 May 2019 14:58:16 -0400
Subject: [PATCH] zasm: make io unit handle PC and output suppression

---
 apps/zasm/instr.asm |  4 ++--
 apps/zasm/io.asm    | 25 +++++++++++++++++++++++--
 apps/zasm/main.asm  | 32 +++++++-------------------------
 3 files changed, 32 insertions(+), 29 deletions(-)

diff --git a/apps/zasm/instr.asm b/apps/zasm/instr.asm
index 7b6fb95..171f987 100644
--- a/apps/zasm/instr.asm
+++ b/apps/zasm/instr.asm
@@ -634,7 +634,7 @@ getUpcode:
 	bit	7, (ix+3)
 	jr	z, .absoluteValue	; bit not set? regular byte value,
 	; Our argument is a relative address ("e" type in djnz and jr). We have
-	; to subtract (ZASM_PC) from it.
+	; to subtract (IO_PC) from it.
 
 	; First, check whether we're on first pass. If we are, skip processing
 	; below because not having real symbol value makes relative address
@@ -645,7 +645,7 @@ getUpcode:
 
 	; We're on second pass
 	push	de		; Don't let go of this, that's our dest
-	ld	de, (ZASM_PC)
+	ld	de, (IO_PC)
 	call	intoHL
 	dec	hl		; what we write is "e-2"
 	dec	hl
diff --git a/apps/zasm/io.asm b/apps/zasm/io.asm
index 7fca734..c9bee13 100644
--- a/apps/zasm/io.asm
+++ b/apps/zasm/io.asm
@@ -4,6 +4,9 @@
 ; parameter, two blockdevs: One that we can read and seek and one that we can
 ; write to (we never seek into it).
 ;
+; This unit also has the responsibility of counting the number of written bytes,
+; maintaining IO_PC and of properly disabling output on first pass.
+;
 ; zasm doesn't buffers its reads during tokenization, which simplifies its
 ; process. However, it also means that it needs, in certain cases, a "putback"
 ; mechanism, that is, a way to say "you see that character I've just read? that
@@ -47,7 +50,8 @@
 ; see ioPutBack below
 .equ	IO_PUTBACK_BUF	IO_INCLUDE_HDL+FS_HANDLE_SIZE
 .equ	IO_IN_INCLUDE	IO_PUTBACK_BUF+1
-.equ	IO_RAMEND	IO_IN_INCLUDE+1
+.equ	IO_PC	IO_IN_INCLUDE+1
+.equ	IO_RAMEND	IO_PC+2
 
 ; *** Code ***
 
@@ -55,7 +59,7 @@ ioInit:
 	xor	a
 	ld	(IO_PUTBACK_BUF), a
 	ld	(IO_IN_INCLUDE), a
-	ret
+	jp	ioResetPC
 
 ioGetC:
 	ld	a, (IO_PUTBACK_BUF)
@@ -101,8 +105,20 @@ ioPutBack:
 	ret
 
 ioPutC:
+	push	hl
+	ld	hl, (IO_PC)
+	inc	hl
+	ld	(IO_PC), hl
+	pop	hl
+	push	af
+	call	zasmIsFirstPass
+	jr	z, .skip
+	pop	af
 	ld	ix, (IO_OUT_PUTC)
 	jp	(ix)
+.skip:
+	pop	af
+	ret
 
 ioSavePos:
 	call	_ioTell
@@ -117,6 +133,11 @@ ioRewind:
 	ld	hl, 0
 	jr	_ioSeek
 
+ioResetPC:
+	ld	hl, 0
+	ld	(IO_PC), hl
+	ret
+
 ; always in absolute mode (A = 0)
 _ioSeek:
 	call	ioInInclude
diff --git a/apps/zasm/main.asm b/apps/zasm/main.asm
index d538298..c1e2a8f 100644
--- a/apps/zasm/main.asm
+++ b/apps/zasm/main.asm
@@ -43,13 +43,11 @@
 ; that when we parse instructions and directive that error out because of a
 ; missing symbol, we don't error out and just write down a dummy value.
 .equ	ZASM_FIRST_PASS		RAMSTART
-; The offset where we currently are with regards to outputting opcodes
-.equ	ZASM_PC			ZASM_FIRST_PASS+1
 ; whether we're in "local pass", that is, in local label scanning mode. During
 ; this special pass, ZASM_FIRST_PASS will also be set so that the rest of the
 ; code behaves as is we were in the first pass.
-.equ	ZASM_LOCAL_PASS		ZASM_PC+2
-; What ZASM_PC was when we started our context
+.equ	ZASM_LOCAL_PASS		ZASM_FIRST_PASS+1
+; What IO_PC was when we started our context
 .equ	ZASM_CTX_PC		ZASM_LOCAL_PASS+1
 .equ	ZASM_RAMEND		ZASM_CTX_PC+2
 
@@ -109,21 +107,11 @@ zasmIsLocalPass:
 	cp	1
 	ret
 
-; Increase (ZASM_PC) by A
-incOutputOffset:
-	push	de
-	ld	de, (ZASM_PC)
-	call	addDE
-	ld	(ZASM_PC), de
-	pop	de
-	ret
-
 ; Repeatedly reads lines from IO, assemble them and spit the binary code in
 ; IO. Z is set on success, unset on error. DE contains the last line number to
 ; be read (first line is 1).
 zasmParseFile:
-	ld	de, 0
-	ld	(ZASM_PC), de
+	call	ioResetPC
 .loop:
 	call	parseLine
 	ret	nz		; error
@@ -142,7 +130,7 @@ zasmParseFile:
 	ret
 
 ; Parse next token and accompanying args (when relevant) in I/O, write the
-; resulting opcode(s) through ioPutC and increases (ZASM_PC) by the number of
+; resulting opcode(s) through ioPutC and increases (IO_PC) by the number of
 ; bytes written. BC is set to the result of the call to tokenize.
 ; Sets Z if parse was successful, unset if there was an error. EOF is not an
 ; error.
@@ -166,9 +154,6 @@ _parseInstr:
 	or	a	; is zero?
 	jr	z, .error
 	ld	b, a		; save output byte count
-	call	incOutputOffset
-	call	zasmIsFirstPass
-	jr	z, .success		; first pass, nothing to write
 	ld	hl, instrUpcode
 .loopInstr:
 	ld	a, (hl)
@@ -189,9 +174,6 @@ _parseDirec:
 	or	a		; cp 0
 	jr	z, .success	; if zero, shortcut through
 	ld	b, a		; save output byte count
-	call	incOutputOffset
-	call	zasmIsFirstPass
-	jr	z, .success		; first pass, nothing to write
 	ld	hl, direcData
 .loopDirec:
 	ld	a, (hl)
@@ -233,7 +215,7 @@ _parseLabel:
 	call	_endLocalPass
 	jr	.success
 .registerLabel:
-	ld	de, (ZASM_PC)
+	ld	de, (IO_PC)
 	call	symRegister
 	jr	nz, .error
 	; continue to .success
@@ -248,7 +230,7 @@ _beginLocalPass:
 	; remember were I/O was
 	call	ioSavePos
 	; Remember where PC was
-	ld	hl, (ZASM_PC)
+	ld	hl, (IO_PC)
 	ld	(ZASM_CTX_PC), hl
 	; Fake first pass
 	ld	a, 1
@@ -268,7 +250,7 @@ _endLocalPass:
 	call	ioRecallPos
 	; recall PC
 	ld	hl, (ZASM_CTX_PC)
-	ld	(ZASM_PC), hl
+	ld	(IO_PC), hl
 	; unfake first pass
 	xor	a
 	ld	(ZASM_FIRST_PASS), a