unpack = String#unpack
Endian = Byte Order
MSB, LSB = bit order
1 byte = 2 nibbles = 8bits
bit
C Ascii = 67 (2^0 + 2^1 + 2^6)
'C'.unpack('b*') # LSB
# => ["11000010"]
'C'.unpack('B*') # MSB
# => ["01000011"]
String to ASCII Values
C* = 8-bit unsigned integer
"hello".unpack('C*')
=> [104, 101, 108, 108, 111]
hex
104.to_s 16 = hex value of the string.
"hello".unpack('C*').map {|e| e.to_s 16}
=> ["68", "65", "6c", "6c", "6f"]
You can also do
> "hello".unpack('H*')
=> ["68656c6c6f"]
"hello".unpack('H*') # high nibble first
=> ["68656c6c6f"]
"hello".unpack('h*')# low nibble first
=> ["8656c6c6f6"]
6 8 # high nibble first
X
8 6 # low nibble first
count
> "hello".unpack('CC')
=> [104, 101]
> "hello".unpack('CCC')
=> [104, 101, 108]
> "hello".unpack('CCCCC')
=> [104, 101, 108, 108, 111]
"aa".unpack('b8B8') # mix MSB and LSB
=> ["10000110", "01100001"]
pack = Array#pack
pack = read the stored data.
[1000001].pack('C') # binary -> 8 bit unsigned integer
=> "A"
['1000001'].pack('b*')
=> "A"
['A'].pack('H') # hex -> Ascii
=> "\xA0" # no Ascii for A0
['a'].pack('H')
=> "\xA0" # in hex, 'A' = 'a'
['a'].pack('h')
=> "\n" # in Ascii table, '\x0A' = new line
Binary File Parsing
or parse image
binary_data = "\x05\x00\x68\x65\x6c\x6c\x6f"
length, message = binary_data.unpack("Sa*")
# [5, "hello"]