From c3cf8166784515eff25e415535628645d402cb66 Mon Sep 17 00:00:00 2001
From: Nao Pross <naopross@thearcway.org>
Date: Wed, 28 Nov 2018 22:39:59 +0100
Subject: Swap bytes (endianness)

The problem with the code until now, was that x64 is little endian.
Therefore when the input buffer is loaded into a register to perform a
bit operation (i.e shift) the result was messed up.
---
 b32e.asm | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

(limited to 'b32e.asm')

diff --git a/b32e.asm b/b32e.asm
index af02dc3..7f0b14a 100644
--- a/b32e.asm
+++ b/b32e.asm
@@ -49,19 +49,19 @@ b32e:
     xor rbx, rbx
 
     ; get a byte from the input
-    mov bl, byte [input_buffer]
+    mov bl, byte [input_buffer + 4]
 
     ; mask and shift to get 5 bits which is a number in 0 ~ 31
     and bl, 0xf8
     shr bl, 3
 
-    ; rshift the input buffer
-    shr qword [input_buffer], 5
+    ; shift left the input buffer
+    shl qword [input_buffer], 5
 
     ; convert to base32
     add rbx, rfc4648
     mov dl, byte [rbx]
-    mov [output_buffer + r11], dl 
+    mov byte [output_buffer + r11], dl 
 
     ; increase counter
     inc r11
@@ -85,6 +85,13 @@ _start:
     cmp rax, 0
     je .exit
 
+    ; swap endianness of input
+    mov rax, qword [input_buffer]
+    bswap rax
+    ; correct position in qword
+    shr rax, 24
+    mov qword [input_buffer], rax
+
     ; convert to base 32
     call b32e
     ; print
-- 
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