openpgp: Rework streaming encryptor.

  - Instead of giving a set of TPKs to the encryptor, hand in a set of
    recipients, which are (keyid, key)-tuples, conveniently created
    from key queries over TPKs.  This simplifies the encryptor, and
    makes the key selection explicit.

  - Drop the EncryptionMode type.

  - As a nice side effect, we can now generate encrypted messages with
    wildcard recipient addresses.

2 files changed, 42 insertions, 22 deletions

diff --git a/openpgp-ffi/include/sequoia/openpgp/serialize.h b/openpgp-ffi/include/sequoia/openpgp/serialize.h
new file mode 100644
index 00000000..7d41d9b0
--- /dev/null
+++ b/openpgp-ffi/include/sequoia/openpgp/serialize.h
@@ -0,0 +1,40 @@
+#ifndef SEQUOIA_OPENPGP_SERIALIZE_H
+#define SEQUOIA_OPENPGP_SERIALIZE_H
+
+/*/
+/// Creates a new recipient with an explicit recipient keyid.
+///
+/// Consumes `keyid`, references `key`.
+/*/
+pgp_recipient_t pgp_recipient_new (pgp_keyid_t keyid, pgp_key_t key);
+
+/*/
+/// Frees this object.
+/*/
+void pgp_recipient_free (pgp_recipient_t);
+
+/*/
+/// Returns a human readable description of this object suitable for
+/// debugging.
+/*/
+char *pgp_recipient_debug (const pgp_recipient_t);
+
+/*/
+/// Gets the KeyID.
+/*/
+pgp_keyid_t pgp_recipient_keyid (const pgp_recipient_t);
+
+/*/
+/// Sets the KeyID.
+/*/
+void pgp_recipient_set_keyid (pgp_recipient_t, pgp_keyid_t);
+
+/*/
+/// Collects recipients from a `pgp_tpk_key_iter_t`.
+///
+/// Consumes the iterator.  The returned buffer must be freed using
+/// libc's allocator.
+/*/
+pgp_recipient_t *pgp_recipients_from_key_iter (pgp_tpk_key_iter_t, size_t *);
+
+#endif
diff --git a/openpgp-ffi/include/sequoia/openpgp/types.h b/openpgp-ffi/include/sequoia/openpgp/types.h
index b6003b1d..d1612a73 100644
--- a/openpgp-ffi/include/sequoia/openpgp/types.h
+++ b/openpgp-ffi/include/sequoia/openpgp/types.h
@@ -445,29 +445,9 @@ typedef struct pgp_tpk_builder *pgp_tpk_builder_t;
 typedef struct pgp_writer_stack *pgp_writer_stack_t;
 
 /*/
-/// Specifies whether to encrypt for archival purposes or for
-/// transport.
+/// A recipient of an encrypted message.
 /*/
-typedef enum pgp_encryption_mode {
-  /*/
-  /// Encrypt data for long-term storage.
-  ///
-  /// This should be used for things that should be decryptable for
-  /// a long period of time, e.g. backups, archives, etc.
-  /*/
-  PGP_ENCRYPTION_MODE_AT_REST = 0,
-
-  /*/
-  /// Encrypt data for transport.
-  ///
-  /// This should be used to protect a message in transit.  The
-  /// recipient is expected to take additional steps if she wants to
-  /// be able to decrypt it later on, e.g. store the decrypted
-  /// session key, or re-encrypt the session key with a different
-  /// key.
-  /*/
-  PGP_ENCRYPTION_MODE_FOR_TRANSPORT = 1,
-} pgp_encryption_mode_t;
+typedef struct pgp_recipient *pgp_recipient_t;
 
 /// Communicates the message structure to the VerificationHelper.
 typedef struct pgp_message_structure *pgp_message_structure_t;