mirror of https://github.com/hsoft/collapseos.git
63 lines
1.9 KiB
NASM
63 lines
1.9 KiB
NASM
|
; ed - line editor
|
||
|
|
;
|
||
|
|
; A text editor modeled after UNIX's ed, but simpler. The goal is to stay tight
|
||
|
|
; on resources and to avoid having to implement screen management code (that is,
|
||
|
|
; develop the machinery to have ncurses-like apps in Collapse OS).
|
||
|
|
;
|
||
|
|
; ed has a mechanism to avoid having to move a lot of memory around at each
|
||
|
|
; edit. Each line is an element in an doubly-linked list and each element point
|
||
|
|
; to an offset in the "scratchpad". The scratchpad starts with the file
|
||
|
|
; contents and every time we change or add a line, that line goes to the end of
|
||
|
|
; the scratch pad and linked lists are reorganized whenever lines are changed.
|
||
|
|
; Contents itself is always appended to the scratchpad.
|
||
|
|
;
|
||
|
|
; That's on a resourceful UNIX system.
|
||
|
|
;
|
||
|
|
; That doubly linked list on the z80 would use 7 bytes per line (prev, next,
|
||
|
|
; offset, len), which is a bit much. Moreover, there's that whole "scratchpad
|
||
|
|
; being loaded in memory" thing that's a bit iffy. We sacrifice speed for
|
||
|
|
; memory usage.
|
||
|
|
;
|
||
|
|
; So here's what we do. First, we have two scratchpads. The first one is the
|
||
|
|
; file being read itself. The second one is is memory, for modifications we
|
||
|
|
; make to the file. When reading the file, we note the offset at which it ends.
|
||
|
|
; All offsets under this limit refer to the first scratchpad. Other offsets
|
||
|
|
; refer to the second.
|
||
|
|
;
|
||
|
|
; Then, our line list if just an array of 16-bit offsets. This means that we
|
||
|
|
; don't have an easy access to line length and we have to move a lot of memory
|
||
|
|
; around whenever we add or delete lines. Hopefully, "LDIR" will be our friend
|
||
|
|
; here...
|
||
|
|
;
|
||
|
|
; *** Requirements ***
|
||
|
|
; printstr
|
||
|
|
; printcrlf
|
||
|
|
; stdioReadC
|
||
|
|
; stdioGetLine
|
||
|
|
|
||
|
|
edMain:
|
||
|
|
edLoop:
|
||
|
|
ld hl, .prompt
|
||
|
|
call printstr
|
||
|
|
.inner:
|
||
|
|
call stdioReadC
|
||
|
|
jr nz, .inner ; not done? loop
|
||
|
|
; We're done. Process line.
|
||
|
|
call printcrlf
|
||
|
|
call stdioGetLine
|
||
|
|
call edProcessLine
|
||
|
|
ret z
|
||
|
|
jr edLoop
|
||
|
|
|
||
|
|
.prompt:
|
||
|
|
.db ":", 0
|
||
|
|
|
||
|
|
; Sets Z if we need to quit
|
||
|
|
edProcessLine:
|
||
|
|
call printstr
|
||
|
|
ld a, (hl)
|
||
|
|
cp 'q'
|
||
|
|
ret z
|
||
|
|
call printcrlf
|
||
|
|
jp unsetZ
|