CODEWITHSUNDEEP
rubystringbinarycharacter-encodingendianness
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Reputation: 6231

Convert a raw string to an array of big-endian words with Ruby

I would like to convert a raw string to an array of big-endian words.

As example, here is a JavaScript function that do it well (by Paul Johnston):

/*
 * Convert a raw string to an array of big-endian words
 * Characters >255 have their high-byte silently ignored.
 */
function rstr2binb(input)
{
  var output = Array(input.length >> 2);
  for(var i = 0; i < output.length; i++)
    output[i] = 0;
  for(var i = 0; i < input.length * 8; i += 8)
    output[i>>5] |= (input.charCodeAt(i / 8) & 0xFF) << (24 - i % 32);
  return output;
}

I believe the Ruby equivalent can be String#unpack(format).

However, I don't know what should be the correct format parameter.

Thank you for any help.

Regards

Upvotes: 2

Views: 1279

Answers (1)

Mladen Jablanović
Mladen Jablanović

Reputation: 44110

I think you should have posted few examples of the input/output pairs. Here's code that gives me the same output as your JS code in Chrome:

/* JS in Chrome: */
rstr2binb('hello world!')
[1751477356, 1864398703, 1919706145]

# irb, Ruby 1.9.1:
'hello world!'.unpack('N*')
#=> [1751477356, 1864398703, 1919706145]

However, I am not sure it will give the same results if you try it on some multibyte characters, unpack shouldn't be ignoring anything.

Upvotes: 2

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