CODEWITHSUNDEEP
rubypack
Cisplatin
Cisplatin

Reputation: 2998

Ruby: What does unpack("C") actually do?

From the docs, unpack does:

Decodes str (which may contain binary data) according to the format string, returning an array of each value extracted.

And the "C" format means 8-bit unsigned (unsigned char).

But what does this actually end up doing to the string I input? What does the result mean, and if I had to do it by hand, how would I go about doing that?

Upvotes: 2

Views: 2600

Answers (2)

matt
matt

Reputation: 535315

But what does this actually end up doing to the string I input

It doesn't do anything to the input. And the input is not really a string here. It's typed as a string, but it is really a buffer of binary data, such as you might receive by networking, and your goal is to extract that data into an array of integers. Example:

s = "\01\00\02\03"
arr = s.unpack("C*")
p(arr) # [1,0,2,3]

That "string" would be meaningless as a string of text, but it is quite viable as a data buffer. Unpacking it allows you examine the data.

Upvotes: 5

Aleksei Matiushkin
Aleksei Matiushkin

Reputation: 121000

It converts each subsequent char to it’s integer ordinal as String#ord does. That said,

string.unpack 'C*'

is an exact equivalent of

string.each_char.map(&:ord)

Upvotes: 7

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