Question

What is the equivalent Scala for the following Python statement? It looks like it’s using an unsigned long or something (which Scala doesn’t have).

size = pack('!L', len(someString))

Answer 1

There’s not an exact one-for-one mapping for this statement, but you can get close.

In Scala, you typically don’t store binary data in a string as pack does. Instead you store it in an Array[Byte].

Scala itself doesn’t have any libraries for this, but Java does, and you can use them in your Scala code.

val out = new java.io.ByteArrayOutputStream()
val writer = new java.io.DataOutputStream(out)
writer.writeInt(someString.length)
writer.close()
val data = out.toByteArray

There are several things to note about why this works:

• DataOutputStream writes in big-endian order, which matches your use of ! in the Python code. If you were writing in little-endian order, you’d have to use a little-endian implementation of DataOutputStream.
• Python’s pack method writes a long as 4 bytes, which matches writeInt in DataOutputStream. writeLong would be the same as long long (q or Q) in pack.