debug.getlocal

3 files changed, 133 insertions, 5 deletions

diff --git a/src/lapi.js b/src/lapi.js
index 3fbcee9..00db461 100644
--- a/src/lapi.js
+++ b/src/lapi.js
@@ -736,6 +736,14 @@ const lua_isuserdata = function(L, idx) {
     return o.ttisfulluserdata(o) || o.ttislightuserdata();
 };
 
+const lua_isthread = function(L, idx) {
+    return lua_type(L, idx) === CT.LUA_TTHREAD;
+};
+
+const lua_isfunction = function(L, idx) {
+    return lua_type(L, idx) === CT.LUA_TFUNCTION;
+};
+
 const lua_rawequal = function(L, index1, index2) {
     let o1 = index2addr(L, index1);
     let o2 = index2addr(L, index2);
@@ -927,6 +935,7 @@ module.exports.lua_getmetatable      = lua_getmetatable;
 module.exports.lua_gettable          = lua_gettable;
 module.exports.lua_gettop            = lua_gettop;
 module.exports.lua_insert            = lua_insert;
+module.exports.lua_isfunction        = lua_isfunction;
 module.exports.lua_isinteger         = lua_isinteger;
 module.exports.lua_isnil             = lua_isnil;
 module.exports.lua_isnone            = lua_isnone;
@@ -934,6 +943,7 @@ module.exports.lua_isnoneornil       = lua_isnoneornil;
 module.exports.lua_isnumber          = lua_isnumber;
 module.exports.lua_isstring          = lua_isstring;
 module.exports.lua_istable           = lua_istable;
+module.exports.lua_isthread          = lua_isthread;
 module.exports.lua_isuserdata        = lua_isuserdata;
 module.exports.lua_len               = lua_len;
 module.exports.lua_load              = lua_load;
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
diff --git a/src/ldebug.js b/src/ldebug.js
index 3d66d85..5a5fc34 100644
--- a/src/ldebug.js
+++ b/src/ldebug.js
@@ -59,6 +59,63 @@ const upvalname = function(p, uv) {
     return s;
 };
 
+const findvararg = function(ci, n, pos) {
+    let nparams = ci.func.p.numparams;
+    if (n >= ci.u.l.base - ci.funcOff - nparams)
+        return null;  /* no such vararg */
+    else {
+        return {
+            pos: ci.funcOff + nparams + n,
+            name: lua.to_luastring("(*vararg)")  /* generic name for any vararg */
+        };
+    }
+};
+
+const findlocal = function(L, ci, n) {
+    let base, name = null;
+
+    if (ci.callstatus & lstate.CIST_LUA) {
+        if (n < 0)  /* access to vararg values? */
+            return findvararg(ci, -n);
+        else {
+            base = ci.u.l.base;
+            name = lfunc.luaF_getlocalname(ci.func.p, n, ci.pcOff);
+        }
+    } else
+        base = ci.funcOff + 1;
+
+    if (name === null) {  /* no 'standard' name? */
+        let limit = ci === L.ci ? L.top : ci.next.func;
+        if (limit - base >= n && n > 0)  /* is 'n' inside 'ci' stack? */
+            name = lua.to_luastring("(*temporary)");  /* generic name for any valid slot */
+        else
+            return null;  /* no name */
+    }
+    return {
+        pos: base + (n - 1),
+        name: name
+    };
+};
+
+const lua_getlocal = function(L, ar, n) {
+    let name;
+    swapextra(L);
+    if (ar === null) {  /* information about non-active function? */
+        if (!L.stack[L.top - 1].ttisLclosure())  /* not a Lua function? */
+            name = null;
+        else  /* consider live variables at function start (parameters) */
+            name = lfunc.luaF_getlocalname(L.stack[L.top - 1].value.p, n, 0);
+    } else {  /* active function; get information through 'ar' */
+        let local = findlocal(L, ar.i_ci, n);
+        name = local.name;
+        let pos = L.stack[local.pos];
+        if (name)
+            L.stack[L.top++] = new TValue(pos.type, pos.value);
+    }
+    swapextra(L);
+    return name;
+};
+
 const funcinfo = function(ar, cl) {
     if (cl === null || cl.type === CT.LUA_TCCL) {
         ar.source = lua.to_luastring("=[JS]");
@@ -503,13 +560,14 @@ const luaG_tointerror = function(L, p1, p2) {
     luaG_runerror(L, lua.to_luastring(`number${lobject.jsstring(varinfo(L, p2))} has no integer representation`));
 };
 
-module.exports.lua_getstack     = lua_getstack;
-module.exports.lua_getinfo      = lua_getinfo;
-module.exports.luaG_errormsg    = luaG_errormsg;
 module.exports.luaG_addinfo     = luaG_addinfo;
-module.exports.luaG_runerror    = luaG_runerror;
-module.exports.luaG_typeerror   = luaG_typeerror;
 module.exports.luaG_concaterror = luaG_concaterror;
+module.exports.luaG_errormsg    = luaG_errormsg;
 module.exports.luaG_opinterror  = luaG_opinterror;
 module.exports.luaG_ordererror  = luaG_ordererror;
+module.exports.luaG_runerror    = luaG_runerror;
 module.exports.luaG_tointerror  = luaG_tointerror;
+module.exports.luaG_typeerror   = luaG_typeerror;
+module.exports.lua_getinfo      = lua_getinfo;
+module.exports.lua_getlocal     = lua_getlocal;
+module.exports.lua_getstack     = lua_getstack;