Added AsynchronousFileChannel suspending extensions

Closes #2

Author: agcom

README.md

@@ -23,6 +23,7 @@ For Maven and Ivy snippets, see the [distribution page](https://bintray.com/agco
 - Suspending extension functions for following classes,
   - `AsynchronousByteChannel`
   - `AsynchronousSocketChannel`
+  - `AsynchronousFileChannel`
 
   The functions are named after their original name plus `await` suffix.
 

lib/src/main/kotlin/io/github/agcom/knio2/AsyncFileChannel.kt

@@ -0,0 +1,46 @@
+package io.github.agcom.knio2
+
+import kotlinx.coroutines.suspendCancellableCoroutine
+import java.nio.ByteBuffer
+import java.nio.channels.AsynchronousFileChannel
+import java.nio.channels.FileLock
+
+/**
+ * Suspending version of [lock][AsynchronousFileChannel.lock] function.
+ *
+ * The operation is not actually cancellable, because the underlying channel ([AsynchronousFileChannel]) provides no guarantee for cancellation.
+ * In case of cancellation, you may ignore the results.
+ */
+public suspend fun AsynchronousFileChannel.lockAwait(
+    position: Long = 0,
+    size: Long = Long.MAX_VALUE,
+    shared: Boolean = false
+): FileLock = suspendCancellableCoroutine {
+    lock(position, size, shared, Unit, it.asCompletionHandler())
+}
+
+/**
+ * Suspending version of [lock][AsynchronousFileChannel.read] function.
+ *
+ * The operation is not actually cancellable, because the underlying channel ([AsynchronousFileChannel]) provides no guarantee for cancellation.
+ * In case of cancellation, you may ignore the results.
+ */
+public suspend fun AsynchronousFileChannel.readAwait(
+    dst: ByteBuffer,
+    position: Long
+): Int = suspendCancellableCoroutine {
+    read(dst, position, Unit, it.asCompletionHandler())
+}
+
+/**
+ * Suspending version of [lock][AsynchronousFileChannel.write] function.
+ *
+ * The operation is not actually cancellable, because the underlying channel ([AsynchronousFileChannel]) provides no guarantee for cancellation.
+ * In case of cancellation, you may ignore the results.
+ */
+public suspend fun AsynchronousFileChannel.writeAwait(
+    src: ByteBuffer,
+    position: Long
+): Int = suspendCancellableCoroutine {
+    write(src, position, Unit, it.asCompletionHandler())
+}