diff --git a/include/cc20.h b/include/cc20.h
index c706c49..75be682 100644
--- a/include/cc20.h
+++ b/include/cc20.h
@@ -41,4 +41,6 @@ int cc20_close_sink(cc20_sink_t* sink,
 
 FILE* cc20_wrap_sink(cc20_sink_t* sink);
 
+size_t cc20_write(const void* ptr, size_t size, size_t nmemb, cc20_sink_t* restrict sink);
+
 #endif /* _CC20_H */
diff --git a/src/ffi.rs b/src/ffi.rs
index 1b697e1..f452987 100644
--- a/src/ffi.rs
+++ b/src/ffi.rs
@@ -4,6 +4,7 @@
 //! Intended to be linked to the C wrapper object `wrapper.c`.
 use super::*;
 use std::ptr;
+use std::ffi::c_void;
 use std::io::{
     self, Write,
 };
@@ -56,6 +57,27 @@ mod interop;
 mod error;
 pub use error::*;
 
+#[no_mangle] pub unsafe extern "C" fn cc20_write(ptr: *const c_void, size: usize, nmemb: usize, sink: *mut CSink) -> usize
+{
+    let mut output: usize = 0;
+    let _er = no_unwind!(ref {
+	let sink = nullchk!(ref mut sink);
+	let bytes = size * nmemb;
+	let slice = if ptr.is_null() {
+	    return CErr::NullPointer;
+	} else {
+	    std::slice::from_raw_parts(ptr as *const u8, bytes)
+	};
+	match sink.sink.write(&slice[..]) {
+	    Err(_) => return CErr::IO,
+	    Ok(v) => output = v,
+	}
+	CErr::Success
+    }).unwrap_or(CErr::Panic);
+    //TODO: Write `er` into an error flag for `sink` (parallel to `ferror`/`feof`).
+    output
+}
+
 #[no_mangle] pub unsafe extern "C" fn cc20_gen_meta(file: *mut libc::FILE, key: *const Key, iv: *const IV, mode: CMode, output: *mut CPassthrough) -> i32
 {
     no_unwind!({
diff --git a/src/ffi/error.rs b/src/ffi/error.rs
index ac06914..edbceba 100644
--- a/src/ffi/error.rs
+++ b/src/ffi/error.rs
@@ -1,6 +1,7 @@
 //! FFI errors
 use super::*;
 
+
 #[derive(Debug, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, Copy)]
 #[repr(C)]
 pub enum CErr
@@ -11,6 +12,8 @@ pub enum CErr
     NullPointer,
     /// Internal SSL error
     SslError,
+    /// I/O error
+    IO,
 
     Panic = -1,
 }
diff --git a/src/ffi/interop.rs b/src/ffi/interop.rs
index a84273c..8060908 100644
--- a/src/ffi/interop.rs
+++ b/src/ffi/interop.rs
@@ -1,7 +1,10 @@
 
 #[macro_export] macro_rules! no_unwind {
     ($expr:expr) => {
-	::std::panic::catch_unwind(move || $expr).ok()
+	::std::panic::catch_unwind(::std::panic::AssertUnwindSafe(move || $expr)).ok()
+    };
+    (ref $expr:expr) => {
+	::std::panic::catch_unwind(::std::panic::AssertUnwindSafe(|| $expr)).ok()
     };
 }