Add olm_session_describe

As a way to dump the state of an olm session, ie. the chain indicies,
so we can debug why olm sessions break and get out of sync.

2 files changed, 14 insertions, 0 deletions

diff --git a/include/olm/olm.h b/include/olm/olm.h
index 61ea07b..770be72 100644
--- a/include/olm/olm.h
+++ b/include/olm/olm.h
@@ -318,6 +318,8 @@ int olm_session_has_received_message(
     OlmSession *session
 );
 
+const char * olm_session_describe(OlmSession * session);
+
 /** Checks if the PRE_KEY message is for this in-bound session. This can happen
  * if multiple messages are sent to this account before this account sends a
  * message in reply. The one_time_key_message buffer is destroyed. Returns 1 if
diff --git a/include/olm/session.hh b/include/olm/session.hh
index 9d44816..86598dd 100644
--- a/include/olm/session.hh
+++ b/include/olm/session.hh
@@ -17,6 +17,8 @@
 
 #include "olm/ratchet.hh"
 
+#define DESCRIBE_BUFFER_LEN 256
+
 namespace olm {
 
 struct Account;
@@ -35,6 +37,8 @@ struct Session {
 
     bool received_message;
 
+    char describe_buffer[DESCRIBE_BUFFER_LEN];
+
     _olm_curve25519_public_key alice_identity_key;
     _olm_curve25519_public_key alice_base_key;
     _olm_curve25519_public_key bob_one_time_key;
@@ -131,6 +135,14 @@ struct Session {
         std::uint8_t const * message, std::size_t message_length,
         std::uint8_t * plaintext, std::size_t max_plaintext_length
     );
+
+    /**
+     * Return a string describing this session and its state (not including the
+     * private key)
+     * The pointer returned refers to an internal buffer which will be valid
+     * up until the next time describe() is called.
+     */
+    const char *describe();
 };