Trying to get pack to work with the * template character

Ruby
1

Ok, here’s a snippet of my code.

@image_array = Array.new
@image = File.open(“test.JPG”, “rb”) do |image|
image.each_byte{|ch| @image_array << ch.to_s}
end
@temp = @image_array.pack(“m*”)

when I display the value of @temp… only the first element of
@image_array has been packed… any idea why the * isn’t working? I
thought the * meant that it would cycle through the entire array and
convert each element… any ideas?

2

John H. wrote:

@image_array = Array.new
@image = File.open(“test.JPG”, “rb”) do |image|
image.each_byte{|ch| @image_array << ch.to_s}
end
@temp = @image_array.pack(“m*”)

I know very little about #pack, so I can’t help you there. However, I
can offer a slightly more terse (faster?) way to get the same array of
strings:

Treat strings as one byte per char ascii

$KCODE=‘a’
File.open( “test.JPG”, “rb” ) do |image|
@image_array = image.read.split(’’).map{ |ch| ch[0].to_s }
end

3

On 11/9/06, John H. [email protected] wrote:

Ok, here’s a snippet of my code.

@image_array = Array.new
@image = File.open(“test.JPG”, “rb”) do |image|
image.each_byte{|ch| @image_array << ch.to_s}
end
@temp = @image_array.pack(“m*”)

Correct me if I guess incorrectly here, but it looks like you want to
base64 encode a JPG image file. Ruby has a nice Base64 class which
will do this for you …

require ‘base64’
@temp = File.open(“test.JPG”, “rb”) {|image| Base64.encode64( image.read
)}

Blessings,
TwP

4

On Fri, 10 Nov 2006 01:21:38 -0000, John H. [email protected] wrote:

thought the * meant that it would cycle through the entire array and
convert each element… any ideas?

As Tim said, ruby does include a base64 library which will probably do
what you want, but if you’re determined to use pack you need to know
that
‘m’ expects a binary string as it’s argument. ‘m*’ expects one or more
binary strings. So in this case, you just need ‘m’ like so:

[File.read('test.JPG')].pack('m')

or possibly:

[File.open('test.JPG','rb') { |f| f.read }].pack('m')