; I/Os in zasm
;
; As a general rule, I/O in zasm is pretty straightforward. We receive, as a
; 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.
;
; On top of that, this unit has the responsibility of keeping track of the
; current lineno. Whenever GetB is called, we check if the fetched byte is a
; newline. If it is, we increase our lineno. This unit is the best place to
; keep track of this because we have to handle ioRecallPos.
;
; 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
; was out of my bounds. Could you make it as if I had never read it?". That
; buffer is one character big and is made with the expectation that ioPutBack
; is always called right after a ioGetB (when it's called).
;
; ioPutBack will mess up seek and tell offsets, so thath "put back" should be
; consumed before having to seek and tell.
;
; That's for the general rules.
;
; Now, let's enter includes. To simplify processing, we make include mostly
; transparent to all other units. They always read from ioGetB and a include
; directive should have the exact same effect as copy/pasting the contents of
; the included file in the caller.
;
; By the way: we don't support multiple level of inclusion. Only top level files
; can include.
;
; When we include, all we do here is open the file with fsOpen and set a flag
; indicating that we're inside an include. When that flag is on, GetB, Seek and
; Tell are transparently redirected to their fs* counterpart.
;
; When we reach EOF in an included file, we transparently unset the "in include"
; flag and continue on the general IN stream.
; *** Variables ***
equ IO_IN_BLK IO_RAMSTART
equ IO_OUT_BLK IO_IN_BLK+BLOCKDEV_SIZE
; Save pos for ioSavePos and ioRecallPos
equ IO_SAVED_POS IO_OUT_BLK+BLOCKDEV_SIZE
; File handle for included source
equ IO_INCLUDE_HDL IO_SAVED_POS+2
; blkdev for include file
equ IO_INCLUDE_BLK IO_INCLUDE_HDL+FS_HANDLE_SIZE
; see ioPutBack below
equ IO_PUTBACK_BUF IO_INCLUDE_BLK+BLOCKDEV_SIZE
equ IO_IN_INCLUDE IO_PUTBACK_BUF+1
equ IO_PC IO_IN_INCLUDE+1
; Current lineno in top-level file
equ IO_LINENO IO_PC+2
; Current lineno in include file
equ IO_INC_LINENO IO_LINENO+2
; Line number (can be top-level or include) when ioSavePos was last called.
equ IO_SAVED_LINENO IO_INC_LINENO+2
; Handle for the ioSpitBin
equ IO_BIN_HDL IO_SAVED_LINENO+2
equ IO_RAMEND IO_BIN_HDL+FS_HANDLE_SIZE
; *** Code ***
ioInit:
xor a
ld (IO_PUTBACK_BUF), a
ld (IO_IN_INCLUDE), a
ld de, IO_INCLUDE_BLK
ld hl, _ioIncBlk
call blkSet
jp ioResetCounters
ioGetB:
ld a, (IO_PUTBACK_BUF)
or a ; cp 0
jr nz, .getback
call ioInInclude
jr z, .normalmode
; We're in "include mode", read from FS
push ix ; --> lvl 1
ld ix, IO_INCLUDE_BLK
call _blkGetB
pop ix ; <-- lvl 1
jr nz, .includeEOF
cp 0x0a ; newline
ret nz ; not newline? nothing to do
; We have newline. Increase lineno and return (the rest of the
; processing below isn't needed.
push hl
ld hl, (IO_INC_LINENO)
inc hl
ld (IO_INC_LINENO), hl
pop hl
ret
includeEOF:
; We reached EOF. What we do depends on whether we're in Local Pass
; mode. Yes, I know, a bit hackish. Normally, we *should* be
; transparently getting of include mode and avoid meddling with global
; states, but here, we need to tell main.asm that the local scope if
; over *before* we get off include mode, otherwise, our IO_SAVED_POS
; will be wrong (an include IO_SAVED_POS used in global IN stream).
call zasmIsLocalPass
ld a, 0 ; doesn't affect Z flag
ret z ; local pass? return EOF
; regular pass (first or second)? transparently get off include mode.
ld (IO_IN_INCLUDE), a ; A already 0
ld (IO_INC_LINENO), a
ld (IO_INC_LINENO+1), a
; continue on to "normal" reading. We don't want to return our zero
normalmode:
; normal mode, read from IN stream
push ix ; --> lvl 1
ld ix, IO_IN_BLK
call _blkGetB
pop ix ; <-- lvl 1
cp LF ; newline
ret nz ; not newline? return
; inc current lineno
push hl
ld hl, IO_LINENO
inc (hl)
pop hl
cp a ; ensure Z
ret
getback:
push af
xor a
ld (IO_PUTBACK_BUF), a
pop af
ret
; Put back non-zero character A into the "ioGetB stack". The next ioGetB call,
; instead of reading from IO_IN_BLK, will return that character. That's the
; easiest way I found to handle the readWord/gotoNextLine problem.
ioPutBack:
ld (IO_PUTBACK_BUF), a
ret
ioPutB:
push hl ; --> lvl 1
ld hl, (IO_PC)
inc hl
ld (IO_PC), hl
pop hl ; <-- lvl 1
push af ; --> lvl 1
call zasmIsFirstPass
jr z, .skip
pop af ; <-- lvl 1
push ix ; --> lvl 1
ld ix, IO_OUT_BLK
call _blkPutB
pop ix ; <-- lvl 1
ret
skip:
pop af ; <-- lvl 1
cp a ; ensure Z
ret
; always in absolute mode (A = 0)
_ioSeek:
call ioInInclude
ld a, 0 ; don't alter flags
jr nz, .include
; normal mode, seek in IN stream
ld ix, IO_IN_BLK
jp _blkSeek
include:
; We're in "include mode", seek in FS
ld ix, IO_INCLUDE_BLK
jp _blkSeek ; returns
_ioTell:
call ioInInclude
jp nz, .include
; normal mode, seek in IN stream
ld ix, IO_IN_BLK
jp _blkTell
include:
; We're in "include mode", tell from FS
ld ix, IO_INCLUDE_BLK
jp _blkTell ; returns
; Sets Z according to whether we're inside an include
; Z is set when we're *not* in includes. A bit weird, I know...
ioInInclude:
ld a, (IO_IN_INCLUDE)
or a ; cp 0
ret
; Open include file name specified in (HL).
; Sets Z on success, unset on error.
ioOpenInclude:
call ioPrintLN
call fsFindFN
ret nz
ld ix, IO_INCLUDE_HDL
call fsOpen
ld a, 1
ld (IO_IN_INCLUDE), a
ld hl, 0
ld (IO_INC_LINENO), hl
xor a
ld ix, IO_INCLUDE_BLK
call _blkSeek
cp a ; ensure Z
ret
; Open file specified in (HL) and spit its contents through ioPutB
; Sets Z on success.
ioSpitBin:
call fsFindFN
ret nz
push hl ; --> lvl 1
ld ix, IO_BIN_HDL
call fsOpen
ld hl, 0
loop:
ld ix, IO_BIN_HDL
call fsGetB
jr nz, .loopend
call ioPutB
inc hl
jr .loop
loopend:
pop hl ; <-- lvl 1
cp a ; ensure Z
ret
; Return current lineno in HL and, if in an include, its lineno in DE.
; If not in an include, DE is set to 0
ioLineNo:
push af
ld hl, (IO_LINENO)
ld de, 0
call ioInInclude
jr z, .end
ld de, (IO_INC_LINENO)
end:
pop af
ret
_ioIncGetB:
ld ix, IO_INCLUDE_HDL
jp fsGetB
_ioIncBlk:
.dw _ioIncGetB, unsetZ
; call printstr followed by newline
ioPrintLN:
call printstr
jp printcrlf
