encoder and decoder now support extendable formats.

src/commonMain/kotlin/net.sergeych.bintools/DataSink.kt

@@ -6,16 +6,41 @@ interface DataSink {
 
     fun writeByte(data: Int) = writeByte(data.toByte())
 
-    open fun writeUByte(data: UByte) {
+    fun writeUByte(data: UByte) {
         writeByte(data.toByte())
     }
 
+    fun writeDouble(value: Double) {
+        writeI64(value.toRawBits())
+    }
+
+    fun writeFloat(value: Float) {
+        writeI32(value.toRawBits())
+    }
+
     @Suppress("unused")
-    open fun writeBytes(data: ByteArray) {
+    fun writeBytes(data: ByteArray) {
         for(d in data) writeByte(d)
     }
 }
 
+inline fun <reified T:Any>DataSink.writeNumber(value: T) {
+    when(value) {
+        is Float -> writeFloat(value)
+        is Double -> writeDouble(value)
+        else -> Smartint.encode(value, this)
+    }
+}
+
+fun DataSink.writeI32(value: Int) {
+    writeBytes(intToBytes(value))
+}
+
+fun DataSink.writeI64(value: Long) {
+    writeBytes(longToBytes(value))
+}
+
+
 class ArrayDataSink : DataSink {
     private val result = mutableListOf<Byte>()