// example.rs

fn main() {
    let doc = pdfdoc::PDFDoc::new("examples/data/LargeTest_0000001.pdf").unwrap();
    doc.merge_xfdf_and_redact("examples/data/LargeTest_0000001.xfdf");
    println!("merged");
}

// pdfdoc.rs
pub struct PDFDoc {
    doc: ffi::TRN_PDFDoc,
}

impl PDFDoc {
    ...
    pub fn merge_xfdf_and_redact(self, xfdf: &str) -> Self {
        let mut fdf: ffi::TRN_FDFDoc = std::ptr::null_mut();
        let xfdf = Ustring::new(xfdf);

        unsafe {
            ffi::TRN_FDFDocCreateFromXFDF(xfdf.to_ustring(), &mut fdf);
            ffi::TRN_PDFDocFDFMerge(self.doc, fdf);
        }

        self
    }
}

impl Drop for PDFDoc {
    fn drop(&mut self) {
        println!("dropped");
        if self.doc != std::ptr::null_mut() {
            unsafe {
                ffi::TRN_PDFDocDestroy(self.doc);
            }
        }
    }
}