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Reverse ttysafe escaping order

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Sending the escape after its target made things complicated for upcoming
stuff I want to add. Although it makes `recv.asm` slightly larger, it's really
worth it.
This commit is contained in:
Virgil Dupras 2020-02-22 14:11:43 -05:00
parent 69f0c6dafd
commit 049f2cf222
2 changed files with 23 additions and 14 deletions
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31
recipes/trs80/recv.asm
View File

@ -1,7 +1,17 @@
ld hl, 0x3000 ; memory address where to put contents.
.equ COM_DRV_ADDR 0x0238 ; replace with *CL's DCB addr
.equ DEST_ADDR 0x3000 ; memory address where to put contents.
; We process the 0x20 exception by pre-putting a mask in the (HL) we're going
; to write to. If it wasn't a 0x20, we put a 0xff mask. If it was a 0x20, we
; put a 0x7f mask.
ld hl, DEST_ADDR
loop:
ld a, 0xff
ld (hl), a ; default mask
loop2:
ld a, 0x03 ; @GET
ld de, 0xffff ; replace with *CL's DCB addr
ld de, COM_DRV_ADDR
rst 0x28
jr nz, maybeerror
or a
@ -9,25 +19,24 @@ loop:
; @PUT that char back
ld c, a
ld a, 0x04 ; @PUT
ld de, 0xffff ; replace with *CL's DCB addr
rst 0x28
jr nz, error
ld a, c
cp 0x20
jr z, adjust
write:
jr z, escapechar
; not an escape char, just apply the mask and write
and (hl)
ld (hl), a
inc hl
jr loop
adjust:
dec hl
ld a, (hl)
and 0x7f
jr write
escapechar:
; adjust by setting (hl) to 0x7f
res 7, (hl)
jr loop2
maybeerror:
; was it an error?
or a
jr z, loop ; not an error, just loop
jr z, loop2 ; not an error, just loop
; error
error:
ld c, a ; Error code from @GET/@PUT

6
tools/ttysafe.c
View File

@ -4,8 +4,8 @@
/* Converts stdin to a content that is "tty safe", that is, that it doesn't
* contain ASCII control characters that can mess up serial communication.
* How it works is that it leaves any char > 0x20 intact, but any char <= 0x20
* is replaced by two chars: char|0x80, 0x20. A 0x20 char always indicate "take
* the char you've just received and unset the 7th bit from it".
* is replaced by two chars: 0x20, then char|0x80. A 0x20 char always indicate
* "take the next char you'll receive and unset the 7th bit from it".
*/
int main(void)
@ -13,8 +13,8 @@ int main(void)
int c = getchar();
while (c != EOF) {
if (c <= 0x20) {
putchar(c|0x80);
putchar(0x20);
putchar(c|0x80);
} else {
putchar(c&0xff);
}