How can I convert a C string that isn't zero termi...

# kotlin-native

[Benjamin Deroche]

How can I convert a C string that isn't zero terminated? The function CPointer<ByteVar>.toKString(): String only work with zero terminated C strings

[ribesg]

The very definition of a C string is an array of characters terminated by the null character

[ribesg]

Wait how can you work with strings not terminated by null, how do you know where they end? Maybe they all have a fixed size?

[Benjamin Deroche]

Because those are C bindings for Rust code, and in Rust strings aren't null terminated. I'm given a struct with the string content and a length, so I ended up looping on the content (which is a CPointer<ByteVar>) until length value, and for each iteration I call content.get(i).toInt().toChar() to get the next char and append it to my StringBuilder

[ribesg]

Well that works but it’s quite heavy. I would create a Kotlin ByteArray of the right size, fill it in one operation and then just String(myByteArray)

[ribesg]

Can’t you just do readBytes(count: Int) on a CPointer? Or maybe it’s on a COpaquePointer

[ribesg]

But COpaquePointer is CPointer<out CPointed> and ByteVar extends CPointed so you can just do String((ptr as COpaquePointer).readBytes(count)) or something like that

[Benjamin Deroche]

readBytes work and give me a ByteArray, but I can't do String(myByteArray) , I get an error Using 'String(CharArray): String' is an error. Use CharArray.concatToString() instead , does I need to convert the ByteArray into a CharArray first?

[ribesg]

I didn’t know about CharArray, maybe String(ByteArray) only works on the JVM. Try myByteArray.stringFromUtf8()

[Benjamin Deroche]

I get unresolved reference for stringFromUtf8 , but either decodeToString or toKString seems to works

[Benjamin Deroche]

val str: CValue<CRustStrView> = Get_version()
    str.useContents {
        val length: Int = len.toInt()
        val test: ByteArray? = data?.readBytes(length)
        println("Received string : '${test?.toKString()}'")
    }

[Benjamin Deroche]

Thank you !

[ribesg]

Oh, there is toKString() on Kotlin’s ByteArray too. Nice

[ribesg]

The way to do that changed like 5 times since Kotlin/Native is a thing

[napperley]

The String (CPointer<ByteVar>) would need to be terminated by some sort of Character, otherwise there would be no way to know where the String ends.