Add padding to output

1 files changed, 21 insertions, 6 deletions

diff --git a/b32e.asm b/b32e.asm
index c7ef93b..8bab796 100644
--- a/b32e.asm
+++ b/b32e.asm
@@ -38,11 +38,18 @@ write_output:
 
 ; b32e
 ; encodes 40 bits (5 bytes) to 8 RFC4648 base32 characters
-; uses reg: rbx, r11
+; uses reg: rax(in: bytes read), rbx, rcx, r11
 ; uses mem: input_buffer, output_buffer
 b32e:
+    ; save the number of bits read in cl
+    mov bl, 8 ; each byte contains 8 bits
+    mul bl
+    mov cl, al
     ; set up output counter
     xor r11, r11
+    ; initialize output buffer with padding
+    mov rbx, 0x3d3d3d3d3d3d3d3d
+    mov qword [output_buffer], rbx
 
 .loop:
     ; clear rbx
@@ -66,12 +73,20 @@ b32e:
     ; increase counter
     inc r11
 
+    ; check number of bits converted >= bits read
+    mov bl, 5 ; each iteration processed 5 bits
+    mov rax, r11
+    mul bl
+    cmp al, cl
+    jge .exit
+
     ; check counter
     ; when the counter reaches 8 it means that 8 characters (40 bits)
     ; have been processed and written
     cmp r11, 8
-    js .loop 
+    jl .loop 
 
+.exit:
     ret
 
 
@@ -86,11 +101,11 @@ _start:
     je .exit
 
     ; swap endianness of input
-    mov rax, qword [input_buffer]
-    bswap rax
+    mov rbx, qword [input_buffer]
+    bswap rbx
     ; correct position in qword
-    shr rax, 24
-    mov qword [input_buffer], rax
+    shr rbx, 24
+    mov qword [input_buffer], rbx
 
     ; convert to base 32
     call b32e