Sharing output streams through a JNI interface

I am writing a Java application that uses a C++ library through a JNI interface. The C++ library creates objects of type Foo, which are duly passed up through JNI to Java.

Suppose the library has an output function

void Foo::print(std::ostream &os)

and I have a Java OutputStream out. How can I invoke Foo::print from Java so that the output appears on out? Is there any way to coerce the OutputStream to a std::ostream in the JNI layer? Can I capture the output in a buffer the JNI layer and then copy it into out?