.section .data
.equ SYS_OPEN, 5
.equ SYS_WRITE, 4
.equ SYS_READ, 3
.equ SYS_CLOSE, 6
.equ SYS_EXIT, 1

.equ O_RDONLY, 0
.equ O_CREAT_WRONLY_TRUNC, 03101

.equ STDIN, 0
.equ STDOUT, 1
.equ STDERR, 2
.equ LINUX_SYSCALL, 0x80
.equ END_OF_FILE, 0
.equ NUMBER_ARGUEMNTS, 2

.section .bss
.equ BUFFER_SIZE, 500
.lcomm BUFFER_DATA, BUFFER_SIZE

.section .text
.equ ST_SIZE_RESERVE, 16
.equ ST_FD_IN, -8
.equ ST_FD_OUT, -16
.equ ST_ARGC, 0
.equ ST_ARGV_1, 8
.equ ST_ARGV_1, 16
.equ ST_ARGV_2, 24

.globl _start
_start:
mov %rsp, %rbp
sub $ST_SIZE_RESERVE, %rsp

open_files:
open_fd_in:
mov $SYS_OPEN, %rax
mov ST_ARGV_1(%rbp), %rbx
mov $O_RDONLY, %rcx
mov $0666, %rdx
int $LINUX_SYSCALL

store_fd_in:
mov %rax, ST_FD_IN(%rbp)

open_fd_out:
mov $SYS_OPEN, %rax
mov ST_ARGV_2(%rbp), %rbx
mov $O_CREAT_WRONLY_TRUNC, %rcx
mov $0666, %rdx
int $LINUX_SYSCALL

store_fd_out:
mov %rax, ST_FD_OUT(%rbp)

read_loop_begin:
mov $SYS_READ, %rax
mov ST_FD_IN(%rbp), %rbx
mov $BUFFER_DATA, %rcx
mov $BUFFER_SIZE, %rdx
int $LINUX_SYSCALL

cmp $END_OF_FILE, %rax
jle end_loop

continue_read_loop:
push $BUFFER_DATA
push %rax
call convert_to_upper
pop %rax
add $4, %rsp
mov %rax, %rdx
mov $SYS_WRITE, %rax
mov ST_FD_OUT(%rbp), %rbx
mov $BUFFER_DATA, %rcx
int $LINUX_SYSCALL
jmp read_loop_begin

end_loop:
mov $SYS_CLOSE, %rax
mov ST_FD_OUT(%rbp), %rbx
int $LINUX_SYSCALL

mov $SYS_CLOSE, %rax
mov ST_FD_IN(%rbp), %rbx
int $LINUX_SYSCALL


.equ LOWERCASE_A, 'a'
.equ  LOWERCASE_Z, 'z'

.equ  UPPER_CONVERSION, 'A' - 'a'

.equ  ST_BUFFER_LEN, 8 #Length of buffer
.equ  ST_BUFFER, 12    #actual buffer

convert_to_upper:
push %rbp
mov %rsp, %rbp

movl ST_BUFFER(%rbp), %eax
mov ST_BUFFER_LEN(%rbp), %rbx
movl $0, %edi
cmp $0, %rbx
je end_convert_loop

convert_loop:
movb (%rax,%rdi,1), %cl
cmpb $LOWERCASE_A, %cl
jl next_byte
cmpb $LOWERCASE_Z, %cl
jg next_byte

addb $UPPER_CONVERSION, %cl
movb %cl, (%rax,%rdi,1)

next_byte:
inc %rdi
cmp %rdi, %rbx
jne convert_loop

end_convert_loop:
mov %rbp, %rsp
pop %rbp
ret