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support backspace when reading line from keyboard

This commit is contained in:
Kartik K. Agaram 2021-10-13 23:15:59 -07:00
parent db0363462f
commit 9a183b8179
3 changed files with 38 additions and 1 deletions
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25
115write-byte.subx
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@ -76,4 +76,29 @@ test-append-byte-single:
# . end
c3/return
undo-append-byte: # f: (addr stream byte)
# . prologue
55/push-ebp
89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp
# . save registers
50/push-eax
# eax = f
8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 0/r32/eax 8/disp8 . # copy *(ebp+8) to eax
# if (f->write <= 0) abort
81 7/subop/compare 0/mod/indirect 0/rm32/eax . . . . . 0/imm32 # compare *eax
7e/jump-if-<= $undo-append-byte:abort/disp8
# --f->write
ff 1/subop/decrement 0/mod/indirect 0/rm32/eax . . . . . . # decrement *eax
$undo-append-byte:end:
# . restore registers
58/pop-to-eax
# . epilogue
89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp
5d/pop-to-ebp
c3/return
$undo-append-byte:abort:
(abort "undo-append-byte: empty stream")
# never gets here
# . . vim:nowrap:textwidth=0

1
400.mu
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@ -65,6 +65,7 @@ sig write-stream-immutable f: (addr stream byte), s: (addr stream byte)
sig read-byte s: (addr stream byte) -> _/eax: byte
sig peek-byte s: (addr stream byte) -> _/eax: byte
sig append-byte f: (addr stream byte), n: int # really just a byte, but I want to pass in literal numbers
sig undo-append-byte f: (addr stream byte) # take most recent append back out
#sig to-hex-char in/eax: int -> out/eax: int
sig append-byte-hex f: (addr stream byte), n: int # really just a byte, but I want to pass in literal numbers
sig write-int32-hex f: (addr stream byte), n: int

13
516read-line.mu
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@ -2,13 +2,24 @@
# abort on stream overflow
fn read-line-from-keyboard keyboard: (addr keyboard), out: (addr stream byte), screen: (addr screen), fg: int, bg: int {
clear-stream out
{
$read-line-from-keyboard:loop: {
draw-cursor screen, 0x20/space
var key/eax: byte <- read-key keyboard
compare key, 0xa/newline
break-if-=
compare key, 0
loop-if-=
compare key, 8/backspace
{
break-if-!=
undo-append-byte out
draw-code-point-at-cursor-over-full-screen screen, 0x20/space, fg 0/bg # clear cursor
move-cursor-left screen
move-cursor-left screen
draw-code-point-at-cursor-over-full-screen screen, 0x20/space, fg 0/bg # clear old cursor
move-cursor-left screen
loop $read-line-from-keyboard:loop
}
var key2/eax: int <- copy key
append-byte out, key2
var c/eax: code-point <- copy key2