1 files changed, 60 insertions, 0 deletions
diff --git a/src/ldblib.js b/src/ldblib.js
index 39b9574..efab872 100644
--- a/src/ldblib.js
+++ b/src/ldblib.js
@@ -5,9 +5,69 @@ const assert  = require('assert');
 const lua     = require('./lua.js');
 const lapi    = require('./lapi.js');
 const lauxlib = require('./lauxlib.js');
+const ldebug  = require('./ldebug.js');
 
+/*
+** If L1 != L, L1 can be in any state, and therefore there are no
+** guarantees about its stack space; any push in L1 must be
+** checked.
+*/
+const checkstack = function(L, L1, n) {
+    if (L !== L1 && !lapi.lua_checkstack(L1, n))
+        lauxlib.luaL_error(L, "stack overflow");
+};
+
+/*
+** Auxiliary function used by several library functions: check for
+** an optional thread as function's first argument and set 'arg' with
+** 1 if this argument is present (so that functions can skip it to
+** access their other arguments)
+*/
+const getthread = function(L) {
+    if (lapi.lua_isthread(L, 1)) {
+        return {
+            arg: 1,
+            thread: lapi.lua_tothread(L, 1)
+        };
+    } else {
+        return {
+            arg: 0,
+            thread: L
+        };  /* function will operate over current thread */
+    }
+};
+
+const db_getlocal = function(L) {
+    let thread = getthread(L);
+    let L1 = thread.thread;
+    let arg = thread.arg;
+    let ar = new lua.lua_Debug();
+    let nvar = lauxlib.luaL_checkinteger(L, arg + 2);  /* local-variable index */
+    if (lapi.lua_isfunction(L, arg + 1)) {
+        lapi.lua_pushvalue(L, arg + 1);  /* push function */
+        lapi.lua_pushstring(L, ldebug.lua_getlocal(L, null, nvar));  /* push local name */
+        return 1;  /* return only name (there is no value) */
+    } else {  /* stack-level argument */
+        let level = lauxlib.luaL_checkinteger(L, arg + 1);
+        if (!ldebug.lua_getstack(L1, level, ar))  /* out of range? */
+            return lauxlib.luaL_argerror(L, arg+1, lapi.to_luastring("level out of range"));
+        checkstack(L, L1, 1);
+        let name = ldebug.lua_getlocal(L1, ar, nvar);
+        if (name) {
+            lapi.lua_xmove(L1, L, 1);  /* move local value */
+            lapi.lua_pushstring(L, name.value);  /* push name */
+            lapi.lua_rotate(L, -2, 1);  /* re-order */
+            return 2;
+        }
+        else {
+            lapi.lua_pushnil(L);  /* no name (nor value) */
+            return 1;
+        }
+    }
+};
 
 const dblib = {
+    "getlocal": db_getlocal
 };
 
 // Only with Node