I have a byte array, for example:
(def g (byte-array (map byte [0 1 2 3])))
How do I get the size of it and how do I prepend this size to the g byte array?
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3 Answers
alength will get you the size.
You'd have to make a new array to prepend it. Here goes:
(def g' (let [len (alength g)
bs (byte-array (inc len))]
(do (System/arraycopy g (int 0) bs (int 1) len)
(aset bs (int 0) len)
bs)))
Comments
The prepending part can be done like this (probably not the best solution):
(def g (byte-array (apply #(cons (byte (count %)) %) [(map byte [0 1 2 3])])))
It returns:
[4, 0, 1, 2, 3]
I think that you should use (alength g) for the length of a Java array.
Of course if your byte array is longer than 255 you will have problems with adding the length as a single byte.
Not sure what you mean about prepending the size, but you can get the size using count
user=> (def g (byte-array (map byte [0 1 2 3])))
#'user/g
user=> (count g)
4
1 Comment
user1676605
Thanks I mean to add the size to the beginning of the array. For google protocol buffers.