Add `JReadableByteChannel`

Summary:
Adds `JReadableByteChannel`, which maps to `java.nio.ReadableByteChannel`.
This class is useful to stream data from Java to C++ memory (in conjunction with `JByteBuffer`).

Differential Revision: D7437312

fbshipit-source-id: 4979706148f0e20228f0f52341fb340497c24a8b

ReactAndroid/src/main/jni/first-party/fb/Android.mk

@@ -13,6 +13,7 @@ LOCAL_SRC_FILES:= \
        jni/jni_helpers.cpp \
        jni/LocalString.cpp \
        jni/OnLoad.cpp \
+       jni/ReadableByteChannel.cpp \
        jni/References.cpp \
        jni/WeakReference.cpp \
        log.cpp \

ReactAndroid/src/main/jni/first-party/fb/include/fb/fbjni/ReadableByteChannel.h

@@ -0,0 +1,23 @@
+/*
+ * Copyright (c) 2016-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#pragma once
+
+#include <fb/fbjni.h>
+#include <fb/fbjni/ByteBuffer.h>
+
+namespace facebook {
+namespace jni {
+
+class JReadableByteChannel : public JavaClass<JReadableByteChannel> {
+public:
+  static constexpr const char* kJavaDescriptor = "Ljava/nio/channels/ReadableByteChannel;";
+
+  int read(alias_ref<JByteBuffer> dest) const;
+};
+
+}}

ReactAndroid/src/main/jni/first-party/fb/jni/ReadableByteChannel.cpp

@@ -0,0 +1,21 @@
+/*
+ * Copyright (c) 2016-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#include <fb/fbjni/ReadableByteChannel.h>
+
+namespace facebook {
+namespace jni {
+
+int JReadableByteChannel::read(alias_ref<JByteBuffer> dest) const {
+  if (!self()) {
+    throwNewJavaException("java/lang/NullPointerException", "java.lang.NullPointerException");
+  }
+  static auto method = javaClassStatic()->getMethod<jint(alias_ref<JByteBuffer>)>("read");
+  return method(self(), dest);
+}
+
+}}