implemented memcached client with Netty

gbcs-common/src/main/kotlin/net/woggioni/gbcs/common/ByteBufInputStream.kt

@@ -0,0 +1,25 @@
+package net.woggioni.gbcs.common
+
+import io.netty.buffer.ByteBuf
+import java.io.InputStream
+
+class ByteBufInputStream(private val buf : ByteBuf) : InputStream() {
+    override fun read(): Int {
+        return buf.takeIf {
+            it.readableBytes() > 0
+        }?.let(ByteBuf::readByte)
+            ?.let(Byte::toInt) ?: -1
+    }
+
+    override fun read(b: ByteArray, off: Int, len: Int): Int {
+        val readableBytes = buf.readableBytes()
+        if(readableBytes == 0) return -1
+        val result = len.coerceAtMost(readableBytes)
+        buf.readBytes(b, off, result)
+        return result
+    }
+
+    override fun close() {
+        buf.release()
+    }
+}