diff --git a/media/ndk/NdkMediaDataSource.cpp b/media/ndk/NdkMediaDataSource.cpp
index 75477b4..43c89bb 100644
--- a/media/ndk/NdkMediaDataSource.cpp
+++ b/media/ndk/NdkMediaDataSource.cpp
@@ -48,6 +48,7 @@
     AMediaDataSourceReadAt readAt;
     AMediaDataSourceGetSize getSize;
     AMediaDataSourceClose close;
+    AMediaDataSourceGetAvailableSize getAvailableSize;
     sp<DataSource> mImpl;
     uint32_t mFlags;
 };
@@ -107,6 +108,17 @@
     }
 }
 
+status_t NdkDataSource::getAvailableSize(off64_t offset, off64_t *sizeptr) {
+    off64_t size = -1;
+    if (mDataSource->getAvailableSize != NULL
+            && mDataSource->userdata != NULL
+            && sizeptr != NULL) {
+        size = mDataSource->getAvailableSize(mDataSource->userdata, offset);
+        *sizeptr = size;
+    }
+    return size >= 0 ? OK : UNKNOWN_ERROR;
+}
+
 static sp<MediaHTTPService> createMediaHttpServiceFromJavaObj(JNIEnv *env, jobject obj, int version) {
     if (obj == NULL) {
         return NULL;
@@ -251,5 +263,11 @@
     return mSource->close(mSource->userdata);
 }
 
+EXPORT
+void AMediaDataSource_setGetAvailableSize(AMediaDataSource *mSource,
+        AMediaDataSourceGetAvailableSize getAvailableSize) {
+    mSource->getAvailableSize = getAvailableSize;
+}
+
 } // extern "C"