How to read bytes from a binary file?

Other
1

I’m using Corona SDK Version 3.0.0, Build 2-16.2906, simulator in Windows10.

I need to read a file, byte by byte

I´ve tried opening the file in “rb” mode:
     Local file, errorString = io.open (PathAndFileName, “rb”)
     byte = file:read ()
     Print (“byte =” … string.format ("%x", byte))
Error: bad argument # 2 to ‘format’ (number expected, got string)
How to solve the problem?

2

Hi. It’s your format() that’s failing. Try it with “%s” rather than “%x”.

3

or, if you’re trying to do the opposite… then you need a “1” in file:read(1), and to print an 8-bit number with your %x you’ll need to string.byte() it first, fe as a “one-liner” with all the pieces you’d need:  print(string.format("%x", string.byte(file:read(1))))

4

Thanks for the tips.
I also checked the book “Programming in Lua” and found a solution:

local FileName, file, errorString, char, byte
FileName = “xxxxx.wav”
PathAndFileName = system.pathForFile(FileName, system.DocumentsDirectory )
file  = io.open( PathAndFileName, “rb” )

bytes = {}
for n = 1, 45 do   – first 45 bytes from file
  char = file:read(1)
  byte = string.byte(char)
  bytes[#bytes+1] = byte
end
io.close(file)

5

Hi. It’s your format() that’s failing. Try it with “%s” rather than “%x”.

6

or, if you’re trying to do the opposite… then you need a “1” in file:read(1), and to print an 8-bit number with your %x you’ll need to string.byte() it first, fe as a “one-liner” with all the pieces you’d need:  print(string.format("%x", string.byte(file:read(1))))

7

Thanks for the tips.
I also checked the book “Programming in Lua” and found a solution:

local FileName, file, errorString, char, byte
FileName = “xxxxx.wav”
PathAndFileName = system.pathForFile(FileName, system.DocumentsDirectory )
file  = io.open( PathAndFileName, “rb” )

bytes = {}
for n = 1, 45 do   – first 45 bytes from file
  char = file:read(1)
  byte = string.byte(char)
  bytes[#bytes+1] = byte
end
io.close(file)