Can't read every byte of binary files on Lua 5.1 - file

Question

,Hello, friends! I've been trying to add compatibility with Lua 5.1 to a library I'm working on and that's written, originally, to Lua 5.3. Everything was going considerably fine until now.
I've stumbled with a behavior I have absolutely no clue about the cause. Here's the thing: apparently, I can't read binary files properly on Lua 5.1. For the sake of clarity, running this test snippet produces different outputs depending on the version it's ran.
local f = io.open("test.bin", "wb")
local t = {}
for i=1, 256 do t[i] = i-1 end
local unpack = unpack or table.unpack
local str = string.char(unpack(t))
f:write(str)
f:close()
f = io.open("test.bin", "rb")
local buffer = {}
for line in f:lines() do
print(#line)
for i=1, #line do
buffer[#buffer+1] = string.byte(line:sub(i,i))
end
end
print('Total:', #buffer)
f:close()
Using Lua 5.1:
245
Total: 245
Using Lua 5.3:
10
245
Total: 255
So, the way I see it is that version 5.1 simply jumps the first "line" of the file for some reason.
Any help will be profoundly appreciated.

Answer 1

This was a bug in Lua 5.1 and Lua 5.2 that was corrected in Lua 5.3.
Anyway, don't use f:lines() with binary files. Instead, read the whole file with f:read("*a")or read it by blocks.