Add rough untested implementation for b32d

1 files changed, 42 insertions, 2 deletions

diff --git a/b32d.asm b/b32d.asm
index aa7582b..1e17582 100644
--- a/b32d.asm
+++ b/b32d.asm
@@ -33,13 +33,53 @@ write_output:
     ret
 
 ; b32d
-; decodes 8 RFC4648 characters without checking its validity (!!!)
-; uses reg:
+; decodes 8 RFC4648 characters (without checking its validity!)
+; uses reg: rax, rbx
 ; uses mem: input_buffer, output_buffer
 b32d:
+    ; reset rax (output)
+    xor rax, rax
+    ; set downwards counter
+    mov bl, 8
+
+.loop:
+    ; get a character
+    mov bh, byte [output_buffer]
+    ; if is padding, exit
+    cmp bh, 0x3d
+    je .exit
+
+    ; shift rax of one byte
+    shl rax, 5
+    ; insert the new 5 bits
+    or al, bh
+
+    ; decrement counter
+    dec bl
+    jnz .loop
+
+.exit:
+    ; save output
+    mov [input_buffer], rax
     ret
 
+
 _start:
+    nop
+
+.loop:
+    ; read input
+    call read_input
+    ; read nothing
+    cmp rax, 0
+    je .exit
+
+    ; decode base32
+    call b32d
+    ; print
+    call write_output
+    jmp .loop
+
 .exit:
     ; linux x64 exit(0)
     mov rax, 60