ffi: Wrap tpk::UserIDBinding.

  - Add sq_user_id_binding_user_id to return the value of the UserID
    from a UserIDBinding.

  - Export an interface to iterate over UserIDBindings,
    sq_tpk_user_id_binding_iter, fn sq_user_id_binding_iter_free,
    sq_user_id_binding_iter_next.

2 files changed, 98 insertions, 1 deletions

diff --git a/ffi/include/sequoia/openpgp.h b/ffi/include/sequoia/openpgp.h
index f898c2a3..c39581c7 100644
--- a/ffi/include/sequoia/openpgp.h
+++ b/ffi/include/sequoia/openpgp.h
@@ -545,6 +545,38 @@ typedef enum sq_reason_for_revocation {
   SQ_REASON_FOR_REVOCATION_FORCE_WIDTH = INT_MAX,
 } sq_reason_for_revocation_t;
 
+/* openpgp::tpk::UserIDBinding.  */
+
+/*/
+/// A `UserIDBinding`.
+/*/
+typedef struct sq_user_id_binding *sq_user_id_binding_t;
+
+/*/
+/// Returns the user id.
+///
+/// This function may fail and return NULL if the user id contains an
+/// interior NUL byte.  We do this rather than complicate the API, as
+/// there is no valid use for such user ids; they must be malicious.
+///
+/// The caller must free the returned value.
+/*/
+char *sq_user_id_binding_user_id (sq_user_id_binding_t binding);
+
+/* openpgp::tpk::UserIDBindingIter.  */
+
+/*/
+/// An iterator over `UserIDBinding`s.
+/*/
+typedef struct sq_user_id_binding_iter *sq_user_id_binding_iter_t;
+
+/*/
+/// Returns the next element in the iterator.
+/*/
+sq_user_id_binding_t sq_user_id_binding_iter_next (sq_user_id_binding_iter_t iter);
+
+/// Frees an sq_user_id_binding_iter_t.
+void sq_user_id_binding_iter_free (sq_user_id_binding_iter_t iter);
 
 /* openpgp::tpk.  */
 
@@ -708,6 +740,11 @@ sq_tpk_t sq_tpk_set_expiry(sq_context_t ctx,
 /*/
 int sq_tpk_is_tsk(sq_tpk_t tpk);
 
+/*/
+/// Returns an iterator over the `UserIDBinding`s.
+/*/
+sq_user_id_binding_iter_t sq_tpk_user_id_binding_iter (sq_tpk_t tpk);
+
 /* TPKBuilder */
 
 typedef struct sq_tpk_builder *sq_tpk_builder_t;
diff --git a/ffi/src/openpgp.rs b/ffi/src/openpgp.rs
index b740e571..34c96806 100644
--- a/ffi/src/openpgp.rs
+++ b/ffi/src/openpgp.rs
@@ -25,7 +25,12 @@ use self::openpgp::{
     },
     crypto::Password,
 };
-use self::openpgp::tpk::{CipherSuite, TPKBuilder};
+use self::openpgp::tpk::{
+    CipherSuite,
+    TPKBuilder,
+    UserIDBinding,
+    UserIDBindingIter,
+};
 use self::openpgp::packet;
 use self::openpgp::parse::{PacketParserResult, PacketParser, PacketParserEOF};
 use self::openpgp::serialize::Serialize;
@@ -982,6 +987,61 @@ pub extern "system" fn sq_revocation_status_free(
     };
 }
 
+/* UserIDBinding */
+
+/// Returns the user id.
+///
+/// This function may fail and return NULL if the user id contains an
+/// interior NUL byte.  We do this rather than complicate the API, as
+/// there is no valid use for such user ids; they must be malicious.
+///
+/// The caller must free the returned value.
+#[no_mangle]
+pub extern "system" fn sq_user_id_binding_user_id(
+    binding: Option<&UserIDBinding>)
+    -> *mut c_char
+{
+    let binding = binding.expect("Binding is NULL");
+
+    if let Ok(c_str) = CString::new(binding.userid().userid()) {
+        c_str.into_raw()
+    } else {
+        ptr::null_mut()
+    }
+}
+
+/* UserIDBindingIter */
+
+/// Returns an iterator over the TPK's user id bindings.
+#[no_mangle]
+pub extern "system" fn sq_tpk_user_id_binding_iter(tpk: Option<&TPK>)
+    -> *mut UserIDBindingIter
+{
+    let tpk = tpk.expect("TPK is NULL");
+    box_raw!(tpk.userids())
+}
+
+/// Frees a sq_user_id_binding_iter_t.
+#[no_mangle]
+pub extern "system" fn sq_user_id_binding_iter_free(
+    iter: *mut UserIDBindingIter)
+{
+    if iter.is_null() { return };
+    unsafe {
+        drop(Box::from_raw(iter))
+    };
+}
+
+/// Returns the next `UserIDBinding`.
+#[no_mangle]
+pub extern "system" fn sq_user_id_binding_iter_next<'a>(
+    iter: Option<&mut UserIDBindingIter<'a>>)
+    -> Option<&'a UserIDBinding>
+{
+    let iter = iter.expect("Iterator is NULL");
+    iter.next()
+}
+
 /* TPKBuilder */
 
 /// Creates a default `sq_tpk_builder_t`.