feat: handle error()s from buffer:read

mqtt.lua

@@ -1,26 +1,36 @@
 local mqtt = {}
 
+local safeRead = function (conn, n)
+    local success, result, err = pcall(conn.read, conn, n)
+    if success then
+        return result, err
+    end
+
+    return nil, result
+end
+
 local readVarint = function (conn, first_byte)
-    local b
+    local b, err
     if first_byte == nil then
-        b = conn:read(1)
+        b, err = safeRead(conn, 1)
     else
         b = first_byte
     end
 
     local n, s = 0, 0
-    while b ~= nil and b & 0x80 == 0x80 do
+    while err == nil and b & 0x80 == 0x80 do
         if s > 21 then
             return 0, "number too large"
         end
 
         n = n + ((b & 0x7F) << s)
         s = s + 7
-        b = conn:read(1)
+
+        b, err = safeRead(conn, 1)
     end
 
-    if b == nil then
-        return n, "eof"
+    if err ~= nil then
+        return n, err
     end
 
     return n + (b << s), nil
@@ -43,6 +53,7 @@ function MqttClient:new (conn)
     self.__index = self
 
     conn.readVarint = readVarint
+    conn.safeRead = safeRead
     conn:setTimeout(1)
 
     c.conn = conn
@@ -53,9 +64,9 @@ function MqttClient:new (conn)
 end
 
 function MqttClient:handle ()
-    local data = self.conn:read(2)
-    if data == nil then
-        return "eof"
+    local data, err = self.conn:safeRead(2)
+    if err ~= nil then
+        return err
     end
 
     local ptype, length, _ = string.unpack("B B", s)
@@ -66,9 +77,9 @@ function MqttClient:handle ()
     end
 
     if length > 0 then
-        data = self.conn:read(length)
-        if data == nil then
-            return "eof"
+        data, err = self.conn:safeRead(length)
+        if err ~= nil then
+            return err
         end
     else
         data = ""