1 files changed, 98 insertions, 0 deletions
diff --git a/include/olm/message.h b/include/olm/message.h
new file mode 100644
index 0000000..e80d54c
--- /dev/null
+++ b/include/olm/message.h
@@ -0,0 +1,98 @@
+/* Copyright 2016 OpenMarket Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * functions for encoding and decoding messages in the Olm protocol.
+ *
+ * Some of these functions have only C++ bindings, and are declared in
+ * message.hh; in time, they should probably be converted to plain C and
+ * declared here.
+ */
+
+#ifndef OLM_MESSAGE_H_
+#define OLM_MESSAGE_H_
+
+#include <stdint.h>
+#include <stddef.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * The length of the buffer needed to hold a group message.
+ */
+size_t _olm_encode_group_message_length(
+    size_t group_session_id_length,
+    uint32_t chain_index,
+    size_t ciphertext_length,
+    size_t mac_length
+);
+
+/**
+ * Writes the message headers into the output buffer.
+ *
+ * version:            version number of the olm protocol
+ * session_id:         group session identifier
+ * session_id_length:  length of session_id
+ * message_index:      message index
+ * ciphertext_length:  length of the ciphertext
+ * output:             where to write the output. Should be at least
+ *                     olm_encode_group_message_length() bytes long.
+ * ciphertext_ptr:     returns the address that the ciphertext
+ *                     should be written to, followed by the MAC.
+ *
+ * Returns the size of the message, up to the MAC.
+ */
+size_t _olm_encode_group_message(
+    uint8_t version,
+    const uint8_t *session_id,
+    size_t session_id_length,
+    uint32_t message_index,
+    size_t ciphertext_length,
+    uint8_t *output,
+    uint8_t **ciphertext_ptr
+);
+
+
+struct _OlmDecodeGroupMessageResults {
+    uint8_t version;
+    const uint8_t *session_id;
+    size_t session_id_length;
+    uint32_t message_index;
+    int has_message_index;
+    const uint8_t *ciphertext;
+    size_t ciphertext_length;
+};
+
+
+/**
+ * Reads the message headers from the input buffer.
+ */
+void _olm_decode_group_message(
+    const uint8_t *input, size_t input_length,
+    size_t mac_length,
+
+    /* output structure: updated with results */
+    struct _OlmDecodeGroupMessageResults *results
+);
+
+
+
+#ifdef __cplusplus
+} // extern "C"
+#endif
+
+#endif /* OLM_MESSAGE_H_ */