add support for lua 5.1

uses a weak-keyed table in the registry to store parent-child mappings,
instead of associated uservalues, which were only added in 5.2.

2 files changed, 65 insertions, 9 deletions

diff --git a/Makefile b/Makefile
index 4b4860a..21d3629 100644
--- a/Makefile
+++ b/Makefile
@@ -1,7 +1,11 @@
 LUA_VER=5.3
 CC = cc
 LD = ld
-CFLAGS = -std=c99 -Wall -O2 -fPIC -I/usr/include/lua$(LUA_VER)
+MORE_CFLAGS=
+ifeq ($(LUA_VER),5.1)
+	MORE_CFLAGS=-DLUA_5_1
+endif
+CFLAGS = $(MORE_CFLAGS) -std=c99 -Wall -O2 -fPIC -I/usr/include/lua$(LUA_VER)
 LFLAGS = -shared -llmdb
 
 lmdb.so: lmdb.o
diff --git a/lmdb.c b/lmdb.c
index d85ce4f..41bb2cf 100644
--- a/lmdb.c
+++ b/lmdb.c
@@ -26,6 +26,10 @@ struct handle {
 			luaL_error(L, "%s", mdb_strerror(__res)); \
 	} while (0)
 
+static void get_parent(lua_State *L, int index);
+static void set_parent(lua_State *L, int index);
+
+
 static void check_valid(lua_State *L, struct handle *h) {
 	if (h->closed) luaL_error(L, "attempt to use expired handle");
 }
@@ -49,6 +53,14 @@ static int version(lua_State *L) {
 	return 3;
 }
 
+#ifdef LUA_5_1 
+lua_Integer lua_tointegerx(lua_State *L, int index, int *isnum) {
+	if (isnum != NULL)
+		*isnum = lua_isnumber(L,index);
+	return lua_tointeger(L, index);
+}
+#endif
+
 static int env_open(lua_State *L) {
 	lua_settop(L, 2);
 	luaL_argcheck(L, lua_isstring(L, 1), 1, "expected string");
@@ -118,7 +130,7 @@ static int env_copy(lua_State *L) {
 static MDB_env *get_env(lua_State *L, int idx) {
 	lua_pushvalue(L, idx);
 	struct handle *ud = NULL;
-	while (lua_getuservalue(L, -1) == LUA_TUSERDATA) {
+	while (get_parent(L, -1), lua_type(L, -1) == LUA_TUSERDATA) {
 		ud = lua_touserdata(L, -1);
 		if (ud->closed) return NULL;
 		check_valid(L, ud);
@@ -161,7 +173,7 @@ static int txn_begin(lua_State *L, bool nested) {
 	lua_setmetatable(L, -2);
 	// store the supplied transaction/env as the parent
 	lua_pushvalue(L, 1);
-	lua_setuservalue(L, -2);
+	set_parent(L, -2);
 
 	ud->has_child = true;
 	return 1;
@@ -185,7 +197,7 @@ static int txn_abort(lua_State *L) {
 	mdb_txn_abort(ud->obj);
 	ud->closed = true;
 
-	lua_getuservalue(L, 1);
+	get_parent(L, 1);
 	struct handle *pud = lua_touserdata(L, -1);
 	pud->has_child = false;
 
@@ -200,7 +212,7 @@ static int txn_commit(lua_State *L) {
 	check_env(L, 1);
 	ud->closed = true;
 
-	lua_getuservalue(L, 1);
+	get_parent(L, 1);
 	struct handle *pud = lua_touserdata(L, -1);
 	pud->has_child = false;
 
@@ -225,7 +237,7 @@ static int db_open(lua_State *L) {
 	lua_setmetatable(L, -2);
 	// transaction is parent of DB handle
 	lua_pushvalue(L, 1);
-	lua_setuservalue(L, -2);
+	set_parent(L, -2);
 	return 1;
 }
 
@@ -245,7 +257,7 @@ static int db_get(lua_State *L) {
 	check_env(L, 1);
 	luaL_argcheck(L, lua_isstring(L, 2), 2, "expected string");
 
-	lua_getuservalue(L, 1);
+	get_parent(L, 1);
 	struct handle *tud = lua_touserdata(L, -1);
 	MDB_val key = toval(L, 2);
 	MDB_val data;
@@ -266,7 +278,7 @@ static int db_put(lua_State *L) {
 	luaL_argcheck(
 		L, lua_isnil(L, 3) || lua_isstring(L, 3), 3, "expected string or nil");
 
-	lua_getuservalue(L, 1);
+	get_parent(L, 1);
 	struct handle *tud = lua_touserdata(L, -1);
 	MDB_val key = toval(L, 2);
 	if (!lua_isnil(L, 3)) {
@@ -283,7 +295,7 @@ static int db_next(lua_State *L) {
 	luaL_argcheck(
 		L, lua_isnil(L, 2) || lua_isstring(L, 2), 2, "expected string or nil");
 
-	lua_getuservalue(L, 1);
+	get_parent(L, 1);
 	struct handle *tud = lua_touserdata(L, -1);
 	MDB_cursor *curs;
 	asserr(mdb_cursor_open(tud->obj, dbi, &curs));
@@ -370,7 +382,11 @@ static const struct luaL_Reg lmdb_db[] = {
 
 static void mt(lua_State *L, const char *name, const struct luaL_Reg l[]) {
 	luaL_newmetatable(L, name);
+#ifdef LUA_5_1
+	luaL_register(L, NULL, l);
+#else
 	luaL_setfuncs(L, l, 0);
+#endif
 	lua_getfield(L, -1, "__index");
 	if (lua_isnil(L, -1)){
 		lua_pop(L, 1);
@@ -379,11 +395,47 @@ static void mt(lua_State *L, const char *name, const struct luaL_Reg l[]) {
 	lua_pop(L, 2);
 }
 
+static void parentmap(lua_State *L) {
+	lua_getfield(L, LUA_REGISTRYINDEX, "lmdb.parentmap");
+}
+
+static void get_parent(lua_State *L, int index) {
+	lua_pushvalue(L, index); // k ... k 
+	parentmap(L); // k ... k t
+	lua_insert(L, -2); // k ... t k 
+	lua_gettable(L, -2); // k ... t v
+	lua_remove(L, -2); // k ... v 
+}
+static void set_parent(lua_State *L, int index) {
+	// references to `index` need to be before anything changes the stack, 
+	// otherwise indices will be off
+	// k ... v 
+	lua_pushvalue(L, index); // k ... v k
+	parentmap(L); // k ... v k t
+	lua_insert(L, -3); // k ... t v k 
+	lua_insert(L, -2); // k ... t k v
+	lua_settable(L, -3); // k ... t 
+	lua_pop(L, 1); // k ...
+}
+
+
 int luaopen_lmdb(lua_State *L) {
 	mt(L, "lmdb.env", lmdb_env);
 	mt(L, "lmdb.txn", lmdb_txn);
 	mt(L, "lmdb.db", lmdb_db);
 
+	lua_newtable(L);
+	lua_newtable(L);
+	lua_pushliteral(L, "k");
+	lua_setfield(L, -2, "__mode");
+	lua_setmetatable(L, -2);
+	lua_setfield(L, LUA_REGISTRYINDEX, "lmdb.parentmap");
+
+#ifdef LUA_5_1
+	lua_newtable(L);
+	luaL_register(L, NULL, lmdb);
+#else
 	luaL_newlib(L, lmdb);
+#endif
 	return 1;
 }