Change Kotlin's bytes type from UByteArray to ByteArray

This reflects the fact that `ByteArray` is a lot more common than
`UByteArray`.

fixtures/coverall/tests/bindings/test_coverall.kts

@@ -14,8 +14,8 @@ import uniffi.coverall.*
 createSomeDict().use { d ->
     assert(d.text == "text")
     assert(d.maybeText == "maybe_text")
-    assert(d.someBytes.contentEquals("some_bytes".toByteArray(Charsets.UTF_8).toUByteArray()))
-    assert(d.maybeSomeBytes.contentEquals("maybe_some_bytes".toByteArray(Charsets.UTF_8).toUByteArray()))
+    assert(d.someBytes.contentEquals("some_bytes".toByteArray(Charsets.UTF_8)))
+    assert(d.maybeSomeBytes.contentEquals("maybe_some_bytes".toByteArray(Charsets.UTF_8)))
     assert(d.aBool)
     assert(d.maybeABool == false)
     assert(d.unsigned8 == 1.toUByte())
@@ -44,7 +44,7 @@ createSomeDict().use { d ->
 createNoneDict().use { d ->
     assert(d.text == "text")
     assert(d.maybeText == null)
-    assert(d.someBytes.contentEquals("some_bytes".toByteArray(Charsets.UTF_8).toUByteArray()))
+    assert(d.someBytes.contentEquals("some_bytes".toByteArray(Charsets.UTF_8)))
     assert(d.maybeSomeBytes == null)
     assert(d.aBool)
     assert(d.maybeABool == null)
@@ -251,5 +251,5 @@ assert(d.integer == 42UL)
 
 // Test bytes
 Coveralls("test_bytes").use { coveralls ->
-    assert(coveralls.reverse("123".toByteArray(Charsets.UTF_8).toUByteArray()).toByteArray().toString(Charsets.UTF_8) == "321")
+    assert(coveralls.reverse("123".toByteArray(Charsets.UTF_8)).toString(Charsets.UTF_8) == "321")
 }

uniffi_bindgen/src/bindings/kotlin/gen_kotlin/primitives.rs

@@ -67,7 +67,7 @@ macro_rules! impl_code_type_for_primitive {
 
 impl_code_type_for_primitive!(BooleanCodeType, "Boolean");
 impl_code_type_for_primitive!(StringCodeType, "String");
-impl_code_type_for_primitive!(BytesCodeType, "UByteArray");
+impl_code_type_for_primitive!(BytesCodeType, "ByteArray");
 impl_code_type_for_primitive!(Int8CodeType, "Byte");
 impl_code_type_for_primitive!(Int16CodeType, "Short");
 impl_code_type_for_primitive!(Int32CodeType, "Int");

uniffi_bindgen/src/bindings/kotlin/templates/ByteArrayHelper.kt

@@ -0,0 +1,15 @@
+public object FfiConverterByteArray: FfiConverterRustBuffer<ByteArray> {
+    override fun read(buf: ByteBuffer): ByteArray {
+        val len = buf.getInt()
+        val byteArr = ByteArray(len)
+        buf.get(byteArr)
+        return byteArr
+    }
+    override fun allocationSize(value: ByteArray): Int {
+        return 4 + value.size
+    }
+    override fun write(value: ByteArray, buf: ByteBuffer) {
+        buf.putInt(value.size)
+        buf.put(value)
+    }
+}

uniffi_bindgen/src/bindings/kotlin/templates/Types.kt

@@ -54,7 +54,7 @@
 {%- include "StringHelper.kt" %}
 
 {%- when Type::Bytes %}
-{%- include "UByteArrayHelper.kt" %}
+{%- include "ByteArrayHelper.kt" %}
 
 {%- when Type::Enum(name) %}
 {% include "EnumTemplate.kt" %}

uniffi_bindgen/src/bindings/kotlin/test.rs

@@ -45,8 +45,6 @@ pub fn run_script(
         .arg("-J-ea")
         // Our test scripts should not produce any warnings.
         .arg("-Werror")
-        // Allow `UByteArray`
-        .arg("-opt-in=kotlin.ExperimentalUnsignedTypes")
         .arg("-script")
         .arg(script_path)
         .args(if args.is_empty() {
@@ -105,8 +103,6 @@ fn build_jar(
     command
         // Our generated bindings should not produce any warnings; fail tests if they do.
         .arg("-Werror")
-        // Allow `UByteArray`
-        .arg("-opt-in=kotlin.ExperimentalUnsignedTypes")
         .arg("-d")
         .arg(&jar_file)
         .arg("-classpath")