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-rw-r--r--src/message.cpp42
1 files changed, 42 insertions, 0 deletions
diff --git a/src/message.cpp b/src/message.cpp
index df0c7bb..ec44262 100644
--- a/src/message.cpp
+++ b/src/message.cpp
@@ -363,3 +363,45 @@ void _olm_encode_group_message(
pos = encode(pos, COUNTER_TAG, chain_index);
pos = encode(pos, CIPHERTEXT_TAG, *ciphertext_ptr, ciphertext_length);
}
+
+void _olm_decode_group_message(
+ const uint8_t *input, size_t input_length,
+ size_t mac_length,
+ struct _OlmDecodeGroupMessageResults *results
+) {
+ std::uint8_t const * pos = input;
+ std::uint8_t const * end = input + input_length - mac_length;
+ std::uint8_t const * unknown = nullptr;
+
+ results->session_id = nullptr;
+ results->session_id_length = 0;
+ bool has_chain_index = false;
+ results->chain_index = 0;
+ results->ciphertext = nullptr;
+ results->ciphertext_length = 0;
+
+ if (pos == end) return;
+ if (input_length < mac_length) return;
+ results->version = *(pos++);
+
+ while (pos != end) {
+ pos = decode(
+ pos, end, GROUP_SESSION_ID_TAG,
+ results->session_id, results->session_id_length
+ );
+ pos = decode(
+ pos, end, COUNTER_TAG,
+ results->chain_index, has_chain_index
+ );
+ pos = decode(
+ pos, end, CIPHERTEXT_TAG,
+ results->ciphertext, results->ciphertext_length
+ );
+ if (unknown == pos) {
+ pos = skip_unknown(pos, end);
+ }
+ unknown = pos;
+ }
+
+ results->has_chain_index = (int)has_chain_index;
+}