Converting a byte array into a hex string
Converting a byte array into a hex string
Surprisingly (to me), this code does not do what I want:
fun ByteArray.toHexString() : String
return this.joinToString("") it.toString(16)
Turns out Byte is signed, so you get negative hex representations for individual bytes, which leads to a completely bogus end result.
Byte
Also, Byte.toString won't pad leading zeroes, which you'd want here.
Byte.toString
What is the simplest (no additional libraries, ideally no extensions) resp. most efficient fix?
@Roland
0xFF.toByte().toString(16)– Moira
Sep 7 '18 at 15:17
0xFF.toByte().toString(16)
@Roland My hint was seeing
- in SHA-256 hashes.– Raphael
Sep 7 '18 at 15:18
-
tried all single byte strings from
0x00 upto 0xFF. All variants on this page produce the same result.. what am I missing here?– Roland
Sep 7 '18 at 15:31
0x00
0xFF
just wondering: how do you get your
ByteArray?– Roland
Sep 7 '18 at 15:43
ByteArray
3 Answers
3
As I am on Kotlin 1.3 you may also be interested in the UByte soon (note that it's an experimental feature. See also Kotlin 1.3M1 and 1.3M2 announcement)
UByte
E.g.:
@ExperimentalUnsignedTypes // just to make it clear that the experimental unsigned types are used
fun ByteArray.toHexString() = asUByteArray().joinToString("") it.toString(16).padStart(2, '0')
The formatting option is probably the nicest other variant (but maybe not that easily readable... and I always forget how it works, so it is definitely not so easy to remember (for me :-)):
fun ByteArray.toHexString() = joinToString("") String.format("%02x", it)
printf does what we want here:
printf
fun ByteArray.toHexString() : String
return this.joinToString("")
java.lang.String.format("%02x", it)
I doubt that you need to spell out
java.lang.String– msrd0
Sep 7 '18 at 23:54
java.lang.String
@msrd0 There is no Java tag on the question. Using KotlinJS I can appreciate when I can rule out an answer like that at the first glance.
– Zackline
Nov 5 '18 at 20:34
@msrd0 I think I wanted to make sure not to pick Kotlin's
String, but it does indeed seem to be unnecessary.– Raphael
Nov 5 '18 at 22:07
String
@Zackline Interesting point. Has any convention for tagging Kotlin questions regarding JVM/JS/Android/Native emerged yet?
– Raphael
Nov 5 '18 at 22:07
fun ByteArray.toHexString() = joinToString("")
Integer.toUnsignedString(java.lang.Byte.toUnsignedInt(it), 16).padStart(2, '0')
Fortunately, Java has toUnsignedString methods on Integer and Long. UNfortunately, these methods are only on Integer and Long, so you need to convert each byte first (using Byte#toUnsignedInt).
toUnsignedString
Integer
Long
Integer
Long
Byte#toUnsignedInt
Thanks for contributing an answer to Stack Overflow!
But avoid …
To learn more, see our tips on writing great answers.
Required, but never shown
Required, but never shown
By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.
... can you give me an input for which you get the bogus output?
– Roland
Sep 7 '18 at 15:17