How to Use the Ruby unpack Method

09/22/2021

Contents

In this article, you will learn how to use the Ruby unpack method.

Using the unpack method

The unpack method in Ruby is a powerful tool for decoding binary data. It allows you to convert binary data into a series of Ruby objects, such as integers, strings, and floats.

The unpack method is available on Ruby strings, and takes a single argument, which is a string that specifies the format of the data you want to unpack. The format string can include a variety of codes that specify the type and size of each piece of data in the binary string.

Here’s an example of using the unpack method to convert a binary string into an integer:

binary_data = "\x01\x02\x03\x04"
integer_data = binary_data.unpack('N')

In this example, binary_data is a string containing four bytes of binary data. The unpack method is called on this string, with the argument ‘N’, which is a code that specifies that we want to convert the data into a 32-bit unsigned integer. The result of the unpack method is an array containing a single element, which is the integer value of the binary data.

Here are some other codes that can be used in the format string:

  • C: 8-bit unsigned integer
  • S: 16-bit unsigned integer
  • L: 32-bit unsigned integer
  • Q: 64-bit unsigned integer
  • c: 8-bit signed integer
  • s: 16-bit signed integer
  • l: 32-bit signed integer
  • q: 64-bit signed integer
  • f: single-precision float
  • d: double-precision float

You can also use these codes in combination with numeric prefixes to specify the size of each piece of data. For example, ‘S4’ would specify a 64-bit unsigned integer.

You can use the unpack method to extract multiple pieces of data from a binary string by including multiple format codes in the format string. For example:

binary_data = "\x01\x02\x03\x04\x05\x06"
integer_data, string_data = binary_data.unpack('N A*')

In this example, binary_data is a string containing six bytes of binary data. The unpack method is called with the argument ‘N A*’, which specifies that we want to extract a 32-bit unsigned integer followed by a string of arbitrary length. The A* code tells unpack to read all remaining bytes in the binary data as a string.

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