Initially and partially implement VertxWriteStreamOutputStream to c…

…onvert the `HttpServerResponse` to an `OutputStream` to be written to by kotlinx.serialization directly and give up

The `OutputStream` methods all deal with byte arrays, and it's still needed to convert byte arrays to buffers. I don't think this can improve the performance.

frameworks/Kotlin/vertx-web-kotlinx/src/main/kotlin/MainVerticle.kt

@@ -19,9 +19,11 @@ import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.launch
 import kotlinx.html.*
 import kotlinx.html.stream.appendHTML
+import kotlinx.serialization.ExperimentalSerializationApi
 import kotlinx.serialization.Serializable
 import kotlinx.serialization.SerializationStrategy
 import kotlinx.serialization.json.Json
+import kotlinx.serialization.json.encodeToStream
 import java.net.SocketException
 import java.time.ZonedDateTime
 import java.time.format.DateTimeFormatter
@@ -117,7 +119,8 @@ class MainVerticle(val hasDb: Boolean) : CoroutineVerticle() {
         checkedCoroutineHandlerUnconfined {
             it.response().run {
                 putJsonResponseHeader()
-                end(Json.encodeToString(serializer, requestHandler(it)))/*.coAwait()*/
+                @OptIn(ExperimentalSerializationApi::class)
+                Json.encodeToStream(serializer, requestHandler(it), toOutputStream())
             }
         }
 

frameworks/Kotlin/vertx-web-kotlinx/src/main/kotlin/VertxWriteStreamOutputStream.kt

@@ -0,0 +1,34 @@
+import io.vertx.core.buffer.Buffer
+import io.vertx.core.streams.WriteStream
+import io.vertx.kotlin.coroutines.coAwait
+import kotlinx.coroutines.runBlocking
+import java.io.OutputStream
+
+class VertxWriteStreamOutputStream(val writeStream: WriteStream<Buffer>) : OutputStream() {
+    override fun write(b: Int) {
+        runBlocking {
+            writeStream.write(Buffer.buffer(4).apply {
+                appendInt(b)
+            }).coAwait()
+        }
+    }
+
+    override fun write(b: ByteArray) {
+        TODO()
+    }
+
+    override fun write(b: ByteArray, off: Int, len: Int) {
+        TODO()
+    }
+
+    override fun close() {
+        TODO()
+    }
+
+    override fun flush() {
+        TODO()
+    }
+}
+
+fun WriteStream<Buffer>.toOutputStream() =
+    VertxWriteStreamOutputStream(this)