1
0
mirror of https://github.com/hsoft/collapseos.git synced 2024-12-26 05:38:06 +11:00
collapseos/apps/lib/fmt.asm
Virgil Dupras 20151a97f8 recipes/rc2014/zasm: use BASIC shell
Also made Makefile actually portable.
2019-12-11 13:01:51 -05:00

116 lines
2.2 KiB
NASM

; *** Requirements ***
; stdioPutC
; divide
;
; Same as fmtDecimal, but DE is considered a signed number
fmtDecimalS:
bit 7, d
jr z, fmtDecimal ; unset, not negative
; Invert DE. spit '-', unset bit, then call fmtDecimal
push de
ld a, '-'
ld (hl), a
inc hl
ld a, d
cpl
ld d, a
ld a, e
cpl
ld e, a
inc de
call fmtDecimal
dec hl
pop de
ret
; Format the number in DE into the string at (HL) in a decimal form.
; Null-terminated. DE is considered an unsigned number.
fmtDecimal:
push ix
push hl
push de
push af
push hl \ pop ix
ex de, hl ; orig number now in HL
ld e, 0
.loop1:
call .div10
push hl ; push remainder. --> lvl E
inc e
ld a, b ; result 0?
or c
push bc \ pop hl
jr nz, .loop1 ; not zero, continue
; We now have C digits to print in the stack.
; Spit them!
push ix \ pop hl ; restore orig HL.
ld b, e
.loop2:
pop de ; <-- lvl E
ld a, '0'
add a, e
ld (hl), a
inc hl
djnz .loop2
; null terminate
xor a
ld (hl), a
pop af
pop de
pop hl
pop ix
ret
.div10:
push de
ld de, 0x000a
call divide
pop de
ret
; Format the lower nibble of A into a hex char and stores the result in A.
fmtHex:
; The idea here is that there's 7 characters between '9' and 'A'
; in the ASCII table, and so we add 7 if the digit is >9.
; daa is designed for using Binary Coded Decimal format, where each
; nibble represents a single base 10 digit. If a nibble has a value >9,
; it adds 6 to that nibble, carrying to the next nibble and bringing the
; value back between 0-9. This gives us 6 of that 7 we needed to add, so
; then we just condtionally set the carry and add that carry, along with
; a number that maps 0 to '0'. We also need the upper nibble to be a
; set value, and have the N, C and H flags clear.
or 0xf0
daa ; now a =0x50 + the original value + 0x06 if >= 0xfa
add a, 0xa0 ; cause a carry for the values that were >=0x0a
adc a, 0x40
ret
; Print the hex char in A as a pair of hex digits.
printHex:
push af
; let's start with the leftmost char
rra \ rra \ rra \ rra
call fmtHex
call stdioPutC
; and now with the rightmost
pop af \ push af
call fmtHex
call stdioPutC
pop af
ret
; Print the hex pair in HL
printHexPair:
push af
ld a, h
call printHex
ld a, l
call printHex
pop af
ret