unpack("N*")

Hi,

I’m trying to unpack a string into network byte order (big-endian), such
as the following method:

Convert an 8-bit or 16-bit string to an array of big-endian words

In 8-bit function, characters >255 have their hi-byte silently

ignored.
def str2binb(str)
bin = []
mask = (1 << 8) - 1
i = 0
while (i < str.length * 8)
bin[i>>5] ||= 0
bin[i>>5] |= (str[i / 8] & mask) << (32 - 8 - i%32)
i += 8
end
bin
end

But after using unpack(“N*”) method (according to
http://www.ruby-doc.org/core/classes/String.html#M000760), the result is
not exactly the same. For instance:

str2binb(“Abcdefghijklmnopqrstuvwxyz”)
=> [1096967012, 1701209960, 1768581996, 1835954032, 1903326068,
1970698104, 2038038528]

“Abcdefghijklmnopqrstuvwxyz”.unpack(“N*”)
=> [1096967012, 1701209960, 1768581996, 1835954032, 1903326068,
1970698104]

Moreover, if I try “a”.unpack(“N*”), Ruby returns a void array…

Thanks for any suggestions.

Zangief I. wrote:

mask = (1 << 8) - 1
http://www.ruby-doc.org/core/classes/String.html#M000760), the result is
not exactly the same. For instance:

str2binb(“Abcdefghijklmnopqrstuvwxyz”)
=> [1096967012, 1701209960, 1768581996, 1835954032, 1903326068,
1970698104, 2038038528]

“Abcdefghijklmnopqrstuvwxyz”.unpack(“N*”)
=> [1096967012, 1701209960, 1768581996, 1835954032, 1903326068,
1970698104]

Moreover, if I try “a”.unpack(“N*”), Ruby returns a void array…

Better pad with null chars (\0) up to a multiple of 4 bytes if you want
the same behavior. I guess unpack(“N*”) stops if there is not a full 4
chars.

Many thanks! :slight_smile:

This forum is not affiliated to the Ruby language, Ruby on Rails framework, nor any Ruby applications discussed here.

| Privacy Policy | Terms of Service | Remote Ruby Jobs