ESP32: MQTT module rewrite (#2629)

* mqtt: first pass

* mqtt: correct gc during callback bug

* mqtt: document and cleanup

* mqtt: separate lnodeaux due to copyright

* mqtt: rename lnodeaux methods

* mqtt: update docs

* mqtt: fix copyright in lnodeaux.c

* mqtt: refactor and cleanup

* mqtt: use ESP logging

components/base_nodemcu/include/lnodeaux.h

@@ -0,0 +1,68 @@
+/*
+ * Copyright (c) 2019 the NodeMCU authors. All rights reserved
+ * 
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ * - Redistributions in binary form must reproduce the above copyright
+ *   notice, this list of conditions and the following disclaimer in the
+ *   documentation and/or other materials provided with the
+ *   distribution.
+ * - Neither the name of the copyright holders nor the names of
+ *   its contributors may be used to endorse or promote products derived
+ *   from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * @author Javier Peletier <jm@epiclabs.io>
+ * @brief This library exports useful functions to handle lua registry refs and strings
+ */
+
+#ifndef _NODEMCU_LNODEAUX_H_
+#define _NODEMCU_LNODEAUX_H_
+
+#include "lua.h"
+
+// lua_ref_t represents a reference to a lua object in the registry
+typedef int lua_ref_t;
+
+//luaX_weak_ref pops an item from the stack and returns a weak reference to it
+lua_ref_t luaX_weak_ref(lua_State* L);
+
+//luaL_push_weak takes a weak reference and pushes the original item on the stack
+void luaX_push_weak_ref(lua_State* L, lua_ref_t ref);
+
+// luaX_alloc_string creates a dynamically-allocated null-terminated string copying it
+// from a lua stack position
+char* luaX_alloc_string(lua_State* L, int idx, int max_length);
+
+// luaX_free_string deallocates memory of a string allocated with luaX_alloc_string
+void luaX_free_string(lua_State* L, char* st);
+
+// luaX_unset_ref unpins a reference to a lua object in the registry
+void luaX_unset_ref(lua_State* L, lua_ref_t* ref);
+
+// luaX_set_ref pins a reference to a lua object, provided a registry
+// or stack position
+void luaX_set_ref(lua_State* L, int idx, lua_ref_t* ref);
+
+// luaX_valid_ref returns true if the reference is set.
+inline bool luaX_valid_ref(lua_ref_t ref) {
+    return ref > 0;
+}
+
+#endif

components/base_nodemcu/lnodeaux.c

@@ -0,0 +1,117 @@
+/*
+ * Copyright (c) 2019 the NodeMCU authors. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ * - Redistributions in binary form must reproduce the above copyright
+ *   notice, this list of conditions and the following disclaimer in the
+ *   documentation and/or other materials provided with the
+ *   distribution.
+ * - Neither the name of the copyright holders nor the names of
+ *   its contributors may be used to endorse or promote products derived
+ *   from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * @author Javier Peletier <jm@epiclabs.io>
+ */
+#include "lnodeaux.h"
+#include <string.h>
+#include "lauxlib.h"
+#include "lmem.h"
+
+// reference to the weak references metatable
+static lua_ref_t weak_mt_ref = LUA_NOREF;
+
+// luaX_weak_ref pops an item from the stack and returns a weak reference to it
+// inspired by https://stackoverflow.com/a/19340846
+lua_ref_t luaX_weak_ref(lua_State* L) {
+    lua_newtable(L);  // push a table on the stack that will serve as proxy of our item
+
+    // Initialize weak metatable if this is the first call
+    if (weak_mt_ref == LUA_NOREF) {
+        lua_newtable(L);  // push a new table on the stack to serve as metatable
+        lua_pushliteral(L, "__mode");
+        lua_pushliteral(L, "v");
+        lua_rawset(L, -3);                             // metatable._mode='v' (values are weak) http://lua-users.org/wiki/WeakTablesTutorial
+        lua_pushvalue(L, -1);                          // duplicate metatable on the stack
+        weak_mt_ref = luaL_ref(L, LUA_REGISTRYINDEX);  // store ref to weak metatable in the registry (pops 1 item)
+    } else {
+        lua_rawgeti(L, LUA_REGISTRYINDEX, weak_mt_ref);  // retrieve metatable from registry
+    }
+
+    lua_setmetatable(L, -2);  // setmetatable(proxy,metatable)
+
+    lua_pushvalue(L, -2);   // push the previous top of stack
+    lua_rawseti(L, -2, 1);  // proxy[1]=original value on top of the stack
+
+    lua_ref_t ref = luaL_ref(L, LUA_REGISTRYINDEX);  // this pops the proxy
+    lua_pop(L, 1);                                   // pop the ref
+    return ref;
+}
+
+//luaL_push_weak takes a weak reference and pushes the original item on the stack
+void luaX_push_weak_ref(lua_State* L, lua_ref_t ref) {
+    if (ref <= 0) {
+        luaL_error(L, "invalid weak ref");
+    }
+    lua_rawgeti(L, LUA_REGISTRYINDEX, ref);  // push the proxy object on the stack
+    lua_rawgeti(L, -1, 1);                   // push proxy[1] (our proxied item) on the stack
+    lua_remove(L, -2);                       // remove proxy from underneath the stack.
+    // Retrieved item remains on top, as output of this function.
+}
+
+// luaX_alloc_string creates a dynamically-allocated null-terminated string copying it
+// from a lua stack position
+char* luaX_alloc_string(lua_State* L, int idx, int max_length) {
+    const char* lua_st = luaL_checkstring(L, idx);  //retrieve string from lua
+                                                    // measure the string and limit it to max_length
+    int len = strlen(lua_st);
+    if (len > max_length)
+        len = max_length;
+
+    // allocate memory for our copy, saving 1 byte to null-terminate it.
+    char* st = luaM_malloc(L, len + 1);
+
+    // actually make a copy
+    strncpy(st, lua_st, len);
+
+    // terminate it with a null char.
+    st[len] = '\0';
+    return st;
+}
+
+// luaX_free_string deallocates memory of a string allocated with luaX_alloc_string
+void luaX_free_string(lua_State* L, char* st) {
+    if (st)
+        luaM_freearray(L, st, strlen(st) + 1, char);
+}
+
+// luaX_unset_ref unpins a reference to a lua object in the registry
+void luaX_unset_ref(lua_State* L, lua_ref_t* ref) {
+    luaL_unref(L, LUA_REGISTRYINDEX, *ref);
+    *ref = LUA_NOREF;
+}
+
+// luaX_set_ref pins a reference to a lua object, provided a registry
+// or stack position
+void luaX_set_ref(lua_State* L, int idx, lua_ref_t* ref) {
+    luaX_unset_ref(L, ref);                      // make sure we free previous reference
+    lua_pushvalue(L, idx);                  // push on the stack the referenced index
+    *ref = luaL_ref(L, LUA_REGISTRYINDEX);  // set the reference (pops 1 value)
+}

docs/modules/mqtt.md

@@ -1,6 +1,7 @@
 # MQTT Module
 | Since  | Origin / Contributor  | Maintainer  | Source  |
 | :----- | :-------------------- | :---------- | :------ |
+| 2019-01-28 | [Javier Peletier](https://github.com/jpeletier) | | [mqtt.c](../../components/modules/mqtt.c)|
 | 2018-10-08 | [Tuan PM](https://github.com/tuanpmt/esp_mqtt), [Espressif](https://docs.espressif.com/projects/esp-idf/en/latest/api-reference/protocols/mqtt.html) | | [mqtt.c](../../components/modules/mqtt.c)|
 
 The client supports version 3.1 and 3.1.1 of the [MQTT](https://en.wikipedia.org/wiki/MQTT) protocol. Make sure that the correct version is set with `make menuconfig` -> "Component config" -> "ESP-MQTT Configurations" -> "Enable MQTT protocol 3.1.1".