Bound and safely serialize PM conversation snapshots

src/dm/dm_core.c

@@ -852,12 +852,13 @@ static void json_escape(const char* src, char* dst, size_t dst_sz) {
 int dm_list_conversations_json(struct UTUN_INSTANCE* inst, char* buf, size_t buf_size, size_t* out_len) {
     struct dm_state* dm = dm_of(inst);
     if (!buf || !out_len || !dm || !dm->db) return -1;
-    int off = 0;
-    off += snprintf(buf + off, buf_size - (size_t)off, "[");
+    *out_len = 0;
+    struct strbuf json = strbuf_new();
+    int failed = strbuf_addf(&json, "[") < 0;
     sqlite3_stmt* st = NULL;
     if (sqlite3_prepare_v2(dm->db,
             "SELECT conv_id, peer_node_id, COALESCE(peer_name,''), last_ts, last_out_seq, last_in_seq"
-            " FROM dm_conversations ORDER BY last_ts DESC",
+            " FROM dm_conversations ORDER BY last_ts DESC LIMIT 200",
             -1, &st, NULL) == SQLITE_OK) {
         int first = 1;
         while (sqlite3_step(st) == SQLITE_ROW) {
@@ -875,18 +876,26 @@ int dm_list_conversations_json(struct UTUN_INSTANCE* inst, char* buf, size_t buf
             }
             char esc_name[512];
             json_escape(name ? name : "", esc_name, sizeof(esc_name));
-            off += snprintf(buf + off, buf_size - (size_t)off,
+            if (strbuf_addf(&json,
                 "%s{\"conv_id\":\"%s\",\"peer_node_id\":%llu,\"peer_name\":\"%s\","
                 "\"last_ts\":%llu,\"out_seq\":%llu,\"in_seq\":%llu}",
                 first ? "" : ",", conv_id, (unsigned long long)peer,
                 esc_name, (unsigned long long)last_ts,
-                (unsigned long long)out_seq, (unsigned long long)in_seq);
+                (unsigned long long)out_seq, (unsigned long long)in_seq) < 0) { failed = 1; break; }
             first = 0;
         }
-    }
+        if (sqlite3_errcode(dm->db) != SQLITE_DONE && sqlite3_errcode(dm->db) != SQLITE_OK) failed = 1;
+    } else failed = 1;
     if (st) sqlite3_finalize(st);
-    off += snprintf(buf + off, buf_size - (size_t)off, "]");
-    *out_len = (size_t)off;
+    if (strbuf_addf(&json, "]") < 0) failed = 1;
+    if (failed || json.len >= buf_size) {
+        DEBUG_ERROR(DEBUG_CATEGORY_DM, "%s: conversations snapshot failed bytes=%zu capacity=%zu sql=%s", DM_ID,
+                    json.len, buf_size, sqlite3_errmsg(dm->db));
+        strbuf_free(&json); return -1;
+    }
+    memcpy(buf, strbuf_str(&json), json.len + 1);
+    *out_len = json.len;
+    strbuf_free(&json);
     return 0;
 }
 
@@ -1017,3 +1026,17 @@ void dm_messages_trampoline(void* arg) {
         chat_event_post(inst, CHAT_EVT_DM_MESSAGES, evt, (int)(1 + cl + len));
     u_free(evt);
 }
+
+void dm_conversations_trampoline(void* arg) {
+    struct dm_conversations_req* req = arg;
+    if (!req) return;
+    struct UTUN_INSTANCE* inst = req->inst;
+    u_free(req);
+    if (!dm_of(inst)) { DEBUG_WARN(DEBUG_CATEGORY_DM, "%s: conversations snapshot after stop", DM_ID); return; }
+    size_t cap = 256 * 1024, len = 0;
+    char* json = u_malloc(cap);
+    if (!json) { DEBUG_ERROR(DEBUG_CATEGORY_DM, "%s: conversations allocation failed", DM_ID); return; }
+    if (!dm_list_conversations_json(inst, json, cap, &len))
+        chat_event_post(inst, CHAT_EVT_DM_CONVERSATIONS, (const uint8_t*)json, (int)len);
+    u_free(json);
+}