From c0828667e70fdd92fd01c581ce04dfc451e01860 Mon Sep 17 00:00:00 2001
From: Sebastian Stal <stal@pyboard.net>
Date: Wed, 7 Aug 2013 10:06:07 -0700
Subject: Document functions, and fix bug.

---
 core/Messenger.c | 15 ++++++++++++++-
 core/Messenger.h | 11 +++++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/core/Messenger.c b/core/Messenger.c
index a4195d58..353ce603 100644
--- a/core/Messenger.c
+++ b/core/Messenger.c
@@ -205,7 +205,10 @@ uint32_t m_sendmessage(int friendnumber, uint8_t *message, uint32_t length)
 {
     if (friendnumber < 0 || friendnumber >= numfriends)
         return 0;
-    return m_sendmessage_withid(friendnumber, friendlist[friendnumber].message_id++, message, length);
+    uint32_t msgid = ++friendlist[friendnumber].message_id;
+    if (msgid == 0)
+        msgid = 1; /* otherwise, false error */
+    return m_sendmessage_withid(friendnumber, msgid, message, length);
 }
 
 uint32_t m_sendmessage_withid(int friendnumber, uint32_t theid, uint8_t *message, uint32_t length)
@@ -391,6 +394,16 @@ static void set_friend_userstatus_kind(int friendnumber, USERSTATUS_KIND k)
     friendlist[friendnumber].userstatus_kind = k;
 }
 
+/* Sets whether we send read receipts for friendnumber. */
+void m_set_sends_receipts(int friendnumber, int yesno)
+{
+    if (yesno < 0 || yesno > 1)
+        return;
+    if (friendnumber >= numfriends || friendnumber < 0)
+        return;
+    friendlist[friendnumber].receives_read_receipts = yesno;
+}
+
 /* static void (*friend_request)(uint8_t *, uint8_t *, uint16_t);
 static uint8_t friend_request_isset = 0; */
 /* set the function that will be executed when a friend request is received. */
diff --git a/core/Messenger.h b/core/Messenger.h
index 0e4eabe0..f0444b91 100644
--- a/core/Messenger.h
+++ b/core/Messenger.h
@@ -171,6 +171,10 @@ int m_copy_self_userstatus(uint8_t *buf, uint32_t maxlen);
 USERSTATUS_KIND m_get_userstatus_kind(int friendnumber);
 USERSTATUS_KIND m_get_self_userstatus_kind(void);
 
+/* Sets whether we send read receipts for friendnumber.
+ * This function is not lazy, and it will fail if yesno is not (0 or 1).*/
+void m_set_sends_receipts(int friendnumber, int yesno);
+
 /* set the function that will be executed when a friend request is received.
     function format is function(uint8_t * public_key, uint8_t * data, uint16_t length) */
 void m_callback_friendrequest(void (*function)(uint8_t *, uint8_t *, uint16_t));
@@ -189,6 +193,13 @@ void m_callback_namechange(void (*function)(int, uint8_t *, uint16_t));
     you are not responsible for freeing newstatus */
 void m_callback_userstatus(void (*function)(int, USERSTATUS_KIND, uint8_t *, uint16_t));
 
+/* set the callback for read receipts
+    function(int friendnumber, uint32_t receipt)
+    if you are keeping a record of returns from m_sendmessage,
+    receipt might be one of those values, and that means the message
+    has been received on the other side. since core doesn't
+    track ids for you, receipt may not correspond to any message
+    in that case, you should discard it. */
 void m_callback_read_receipt(void (*function)(int, uint32_t));
 
 /* run this at startup
-- 
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