cezar asm

# Szyfr Cezara
# %dl klucz dla liter
# %dh klucz dla liczb
.data
SYSREAD = 0
SYSWRITE = 1
SYSEXIT = 60

STDIN = 0
STDOUT = 1

EXIT_SUCCESS = 0
EXIT_ERR = 1
BUFLEN = 512
KEY = 53
ZCODE = 0x30    # zero code
NCODE = 0x3A    # nine code + 1
BACODE = 0x41   # A code
BZCODE = 0x5B   # Z code + 1
SACODE = 0x61   # a code
SZCODE = 0x7B   # z code + 1
LETTER_FIX = 26
NUMBER_FIX = 10

key: .ascii "26"
key_len = .-key
err_msg: .ascii "Klucz zawiera niedozwolone znaki\n"
err_msg_len = .-err_msg

.bss
.comm textin, 512
.comm textout, 512
.comm lkey, 1
.comm nkey, 1

.text
.global main

main:
nop
movq $SYSREAD, %rax
movq $STDIN, %rdi
movq $textin, %rsi
movq $BUFLEN, %rdx
syscall

movq $0, %rdx
movq %rax, %r8
dec %r8 # pokazuje na '\n'
movq $0, %rdi   # licznik

make_key:
# %cl znak
# %r10 wartosc klucza
movb $10, %al
movw $0, %cx
movb key(,%rdi,1), %cl
cmp $ZCODE, %cl
jl err_end
cmp $NCODE, %cl
jge err_end
subw $ZCODE, %cx
movw %r10w, %dx
mulw %dx
movw %ax, %dx
addw %cx, %dx
addw %dx, %r10w
inc %rdi
cmp $key_len, %rdi
jne make_key

#dzielenie klucza

movq $0, %rdx
movq %r10, %rax
movq $26, %rbx
divq %rbx
movq %rdx, %r11

movq $0, %rdx
movw %r10w, %ax
movw $10, %bx
divw %bx
movw %dx, %r12w

movq $0, %rdi
loop:
cmp %rdi, %r8
je end

movb textin(,%rdi, 1), %cl  # n

# 0<n<9 ?
movb $ZCODE, %bl
movb $NCODE, %bh
cmp %cl, %bl
jg no_change
cmp %cl, %bh
jg change_number

# A<n<Z ?
movb $BACODE, %bl
movb $BZCODE, %bh
cmp %cl, %bl
jg no_change
cmp %cl, %bh
jg change_letter
jmp no_change

change_letter:
add %r11b, %cl
# n>Z?
cmp $'Z', %cl
jg letter_overflow
movb %cl, textout(,%rdi, 1)
inc %rdi
jmp loop

letter_overflow:
subb $LETTER_FIX, %cl
# n>Z?
cmp $'Z', %cl
jg letter_overflow
movb %cl, textout(,%rdi, 1)
inc %rdi
jmp loop

change_number:
add %r12b, %cl
# n>9?
cmp $'9', %cl
jg number_overflow
movb %cl, textout(,%rdi, 1)
inc %rdi
jmp loop

number_overflow:
subb $NUMBER_FIX, %cl
# n>9?
cmp $'9', %cl
jg number_overflow
movb %cl, textout(,%rdi, 1)
inc %rdi
jmp loop

no_change:
movb %cl, textout(,%rdi,1)
inc %rdi
jmp loop

end:
movb $'\n', textout(,%rdi,1)
movq $SYSWRITE, %rax
movq $STDOUT, %rdi
movq $textout, %rsi
movq $BUFLEN, %rdx
syscall

movq $SYSEXIT, %rax
movq $EXIT_SUCCESS, %rdi
syscall

err_end:
movq $SYSWRITE, %rax
movq $STDOUT, %rdi
movq $err_msg, %rsi
movq $err_msg_len, %rdx
syscall

movq $SYSEXIT, %rax
movq $EXIT_ERR, %rdi
syscall