mirror of https://github.com/hsoft/collapseos.git
116 lines
2.2 KiB
NASM
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
|