Hello -- I'm trying to write out specific byte sequences over the
wire / to a file / etc. Let's say for example that I wanted to write
out
99 111 108 108 105 110
as a simple, six byte sequence to a file. In Java, I might use the
byte primitive, but it seems that in Ruby you have Fixnum and then a
Float for fractions. If I simply create a Fixnum using the 99
literal, I think that that will create more than an 8-bit sequence
when I write out to the file.
Any ideas on how to do this?
String objects are arrays of bytes, so you could simply do...
num_string = "99 111 108 108 105 110"
byte_string = num_string.split.map! {|word| word.to_i.chr}.join
# Now, to illustrate...
byte_string.class
# gives String
byte[0]
# gives 99, the base 10 representation of 1100011
# note that each byte can store numbers up to 255
puts byte_string
# gives collin
If you want to store the 1's and 0's as a text string, you can use the
Integer#to_s(2) method.
hth,
Todd
On 11/6/07, Collin VanDyck <gluedtomyseat@gmail.com> wrote:
Hello -- I'm trying to write out specific byte sequences over the
wire / to a file / etc. Let's say for example that I wanted to write
out99 111 108 108 105 110
as a simple, six byte sequence to a file. In Java, I might use the
byte primitive, but it seems that in Ruby you have Fixnum and then a
Float for fractions. If I simply create a Fixnum using the 99
literal, I think that that will create more than an 8-bit sequence
when I write out to the file.Any ideas on how to do this?
Hello -- I'm trying to write out specific byte sequences over the
wire / to a file / etc. Let's say for example that I wanted to write
out99 111 108 108 105 110
as a simple, six byte sequence to a file. In Java, I might use the
byte primitive, but it seems that in Ruby you have Fixnum and then a
Float for fractions. If I simply create a Fixnum using the 99
literal, I think that that will create more than an 8-bit sequence
when I write out to the file.Any ideas on how to do this?
I *think* you'll want to use Array#pack. E.g., to write them out in
big-endian order:
a = [99, 111, 108, 108, 105, 110].pack 'n*'
=> "\000c\000o\000l\000l\000i\000n"
file.write a
If you want little-endian, use 's*' (or 'S*' for unsigned) instead of
'n*'. See RDoc Documentation and check Array#pack for more
details on the directives.
On Nov 6, 6:42 pm, Collin VanDyck <gluedtomys...@gmail.com> wrote:
Thank you for your replies!
Both methods seem to work equally well, but I'm seeming to favor the
pack method because i can just push in my random bytes (0-255) into an
array. I decided to use pack "C*" though, because I think that the C*
directive will limit the packed members to 8 bits, if I'm not mistaken.
Hmm, I was thinking about #pack, but your example creates 12 bytes.
On 11/6/07, yermej <yermej@gmail.com> wrote:
On Nov 6, 6:42 pm, Collin VanDyck <gluedtomys...@gmail.com> wrote:
> Hello -- I'm trying to write out specific byte sequences over the
> wire / to a file / etc. Let's say for example that I wanted to write
> out
>
> 99 111 108 108 105 110
>
> as a simple, six byte sequence to a file. In Java, I might use the
> byte primitive, but it seems that in Ruby you have Fixnum and then a
> Float for fractions. If I simply create a Fixnum using the 99
> literal, I think that that will create more than an 8-bit sequence
> when I write out to the file.
>
> Any ideas on how to do this?I *think* you'll want to use Array#pack. E.g., to write them out in
big-endian order:> a = [99, 111, 108, 108, 105, 110].pack 'n*'
=> "\000c\000o\000l\000l\000i\000n"
> file.write aIf you want little-endian, use 's*' (or 'S*' for unsigned) instead of
'n*'. See RDoc Documentation and check Array#pack for more
details on the directives.
Good choice!
Todd
On 11/6/07, Collin VanDyck <gluedtomyseat@gmail.com> wrote:
Thank you for your replies!
Both methods seem to work equally well, but I'm seeming to favor the
pack method because i can just push in my random bytes (0-255) into an
array. I decided to use pack "C*" though, because I think that the C*
directive will limit the packed members to 8 bits, if I'm not mistaken.
Todd Benson wrote:
On 11/6/07, yermej <yermej@gmail.com> wrote:
On Nov 6, 6:42 pm, Collin VanDyck <gluedtomys...@gmail.com> wrote:
Hello -- I'm trying to write out specific byte sequences over the
wire / to a file / etc. Let's say for example that I wanted to write
out99 111 108 108 105 110
as a simple, six byte sequence to a file. In Java, I might use the
byte primitive, but it seems that in Ruby you have Fixnum and then a
Float for fractions. If I simply create a Fixnum using the 99
literal, I think that that will create more than an 8-bit sequence
when I write out to the file.Any ideas on how to do this?
I *think* you'll want to use Array#pack. E.g., to write them out in
big-endian order:a = [99, 111, 108, 108, 105, 110].pack 'n*'
=> "\000c\000o\000l\000l\000i\000n"
file.write a
If you want little-endian, use 's*' (or 'S*' for unsigned) instead of
'n*'. See RDoc Documentation and check Array#pack for more
details on the directives.Hmm, I was thinking about #pack, but your example creates 12 bytes.
That's because n isn't the code for a byte - you want c or C, for signed or unsigned char:
irb(main):004:0> a = [1, 2, 3, 4, 5, 6].pack 'C*'
=> "\001\002\003\004\005\006"
--
Alex