Support SAF properly

app/src/main/java/org/schabi/newpipe/streams/io/SharpInputStream.java

@@ -0,0 +1,48 @@
+package org.schabi.newpipe.streams.io;
+
+import androidx.annotation.NonNull;
+
+import java.io.IOException;
+import java.io.InputStream;
+
+public class SharpInputStream extends InputStream {
+    private final SharpStream stream;
+
+    public SharpInputStream(final SharpStream stream) throws IOException {
+        if (!stream.canRead()) {
+            throw new IOException("SharpStream is not readable");
+        }
+        this.stream = stream;
+    }
+
+    @Override
+    public int read() throws IOException {
+        return stream.read();
+    }
+
+    @Override
+    public int read(@NonNull final byte[] b) throws IOException {
+        return stream.read(b);
+    }
+
+    @Override
+    public int read(@NonNull final byte[] b, final int off, final int len) throws IOException {
+        return stream.read(b, off, len);
+    }
+
+    @Override
+    public long skip(final long n) throws IOException {
+        return stream.skip(n);
+    }
+
+    @Override
+    public int available() {
+        final long res = stream.available();
+        return res > Integer.MAX_VALUE ? Integer.MAX_VALUE : (int) res;
+    }
+
+    @Override
+    public void close() {
+        stream.close();
+    }
+}

app/src/main/java/org/schabi/newpipe/streams/io/SharpOutputStream.java

@@ -0,0 +1,42 @@
+package org.schabi.newpipe.streams.io;
+
+import androidx.annotation.NonNull;
+
+import java.io.IOException;
+import java.io.OutputStream;
+
+public class SharpOutputStream extends OutputStream {
+    private final SharpStream stream;
+
+    public SharpOutputStream(final SharpStream stream) throws IOException {
+        if (!stream.canWrite()) {
+            throw new IOException("SharpStream is not writable");
+        }
+        this.stream = stream;
+    }
+
+    @Override
+    public void write(final int b) throws IOException {
+        stream.write((byte) b);
+    }
+
+    @Override
+    public void write(@NonNull final byte[] b) throws IOException {
+        stream.write(b);
+    }
+
+    @Override
+    public void write(@NonNull final byte[] b, final int off, final int len) throws IOException {
+        stream.write(b, off, len);
+    }
+
+    @Override
+    public void flush() throws IOException {
+        stream.flush();
+    }
+
+    @Override
+    public void close() {
+        stream.close();
+    }
+}

app/src/main/java/org/schabi/newpipe/streams/io/SharpStream.java

@@ -1,12 +1,13 @@
 package org.schabi.newpipe.streams.io;
 
 import java.io.Closeable;
+import java.io.Flushable;
 import java.io.IOException;
 
 /**
  * Based on C#'s Stream class.
  */
-public abstract class SharpStream  implements Closeable {
+public abstract class SharpStream implements Closeable, Flushable {
     public abstract int read() throws IOException;
 
     public abstract int read(byte[] buffer) throws IOException;