Ruby: Split binary data

Question

I want to split data to chunks of let's say 8154 byte:

data = Zlib::Deflate.deflate(some_very_long_string)

What would be the best way to do that?

I tried to use this:

chunks = data.scan /.{1,8154}/

...but data was lost! data had a size of 11682, but when looping through every chunk and summing up the size I ended up with a total size of 11677. 5 bytes were lost! Why?

Answer 1

Regexps are not a good way to parse binary data. Use bytes and each_slice to operate bytes. And use pack 'C*' to convert them back into strings for output or debug:

irb> data = File.open("sample.gif", "rb", &:read)
=> "GIF89a\r\x00\r........."

irb> data.bytes.each_slice(10){ |slice| p slice, slice.pack("C*") }
[71, 73, 70, 56, 57, 97, 13, 0, 13, 0]
"GIF89a\r\x00\r\x00"
[247, 0, 0, 0, 0, 0, 0, 0, 51, 0]
"\xF7\x00\x00\x00\x00\x00\x00\x003\x00"
...........