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section .data
rfc4648 db 'ABCDEFGHIJKLMNOPQRSTUVWXYZ234567'
section .bss
input_buffer resb 5
output_buffer resb 8
section .text
global _start
; read_input
; reads 5 bytes (40 bits) of input
read_input:
; linux x64 read(stdin, input_buffer, 5)
mov rax, 0
mov rdi, 0
mov rsi, input_buffer
mov rdx, 5
syscall
ret
; write_output
; writes the output buffer to stdout
write_output:
; linux x64 write(stdout, output_buffer, 8)
mov rax, 1
mov rdi, 1
mov rsi, output_buffer
mov rdx, 5
syscall
ret
; b32e
; encodes 40 bits (5 bytes) to 8 RFC4648 base32 characters
; inputs: bl=5 bits
; uses: rxb, rdx, r11
b32e:
; set up outputs counter
xor r11, r11
.loop:
; get 5 bits from the input
xor rbx, rbx
mov bl, byte [input_buffer]
and bl, 0x1f
; rshift the input buffer
; convert to base32
add rbx, rfc4648
mov dl, byte [rbx]
mov byte [output_buffer + r11], dl
; increase counter
inc r11
cmp r11, 8
js .loop
ret
_start:
nop
call read_input
call b32e
call write_output
.exit:
; linux x64 exit(0)
mov rax, 60
mov rdi, 0
syscall
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