clj-struct

This is almost Python's struct module in Clojure. You can easily converse between Clojure value and bytes stream which come from file, network ...etc.

How to use it

(ns your-package
  (:require [clj-struct.core :as clj-struct]))

pack

use 'pack' function to encode clojure value to a sequence of bytes

(clj-struct/pack "c?I" \a true 32767)
;;> the output will be a sequence of byte corresponding to format "c?I" and value

The first parameter is a format (format detail see below), and rest parameters are corresponding values. In above example, format "c?I" means three Clojure value: a character, a boolean and a unsigned integer, and rest of parameters are that three values.

unpack

use "unpack" to decode a sequence of bytes to clojure values

(clj-struct/unpack "c?I" your-bytes)
;;; here the your-bytes should be a sequence of bytes read from network,
;;; file or other source. Output will be three Clojure value: a chatacter value, a boolean value and a long value

Format syntax

Starting with Order Type

The first character of format can be use to specify the byte order, little-endian or big-endian. For example

"<f"

means Float type with little-endian order. The Byte Order is optional, default is big-endian.

There are three options:

• < : little-endian

• : big-endian

• ! : network (= big-endian). This is available for those poor souls who claim they can’t remember whether network byte order is big-endian or little-endian.

Data type

After Order type is one or many Data Type. Available Data type are:

• c : character, byte size is 1, corresponding Clojure type is Character
• b : signed char, byte size is 1, corresponding Clojure type is Integer
• B : unsigned character, size is 1, corresponding Clojure type is Integer
• ? : boolean. size is 1, corresponding Clojure type is Boolean
• h : short. Size is 2, corresponding Clojure type is Integer
• H : unsigned short. Size is 2, corresponding Clojure type is Integer
• i : integer. Size is 4, corresponding Clojure type is Long
• I : unsigned integer. Size is 4, corresponding Clojure type is Long.
• l : long. Size is 8, corresponding Clojure type is BigInt
• L : unsigned long. Size is 8, corresponding Clojure type is BigInt
• f : float. Size is 4. Clojure type is Float.
• d : double. Size is 8. Clojure type is Double.

Count of Data type

You can have a count before data type, for example "3i2H" is equal "iiiHH"