pcall, xpcall

2 files changed, 79 insertions, 7 deletions

diff --git a/src/lapi.js b/src/lapi.js
index 907d2b1..9059ee9 100644
--- a/src/lapi.js
+++ b/src/lapi.js
@@ -30,7 +30,7 @@ const lua_atpanic = function(L, panicf) {
     return old;
 };
 
-// Return real index on stack
+// Return value for idx on stack
 const index2addr = function(L, idx) {
     let ci = L.ci;
     if (idx > 0) {
@@ -54,6 +54,30 @@ const index2addr = function(L, idx) {
     }
 };
 
+// Like index2addr but returns the index on stack
+const index2addr_ = function(L, idx) {
+    let ci = L.ci;
+    if (idx > 0) {
+        let o = ci.funcOff + idx;
+        assert(idx <= ci.top - (ci.funcOff + 1), "unacceptable index");
+        if (o >= L.top) return null;
+        else return o;
+    } else if (idx > lua.LUA_REGISTRYINDEX) {
+        assert(idx !== 0 && -idx <= L.top, "invalid index");
+        return L.top + idx;
+    } else if (idx === lua.LUA_REGISTRYINDEX) {
+        return null;
+    } else { /* upvalues */
+        idx = lua.LUA_REGISTRYINDEX - idx;
+        assert(idx <= MAXUPVAL + 1, "upvalue index too large");
+        if (ci.func.ttislcf()) /* light C function? */
+            return null; /* it has no upvalues */
+        else {
+            return idx <= ci.func.nupvalues ? idx - 1 : null;
+        }
+    }
+};
+
 const lua_checkstack = function(L, n) {
     return L.stack.length < luaconf.LUAI_MAXSTACK;
 };
@@ -99,7 +123,7 @@ const lua_pop = function(L, n) {
 }
 
 const reverse = function(L, from, to) {
-    for (; from < to; from++, to --) {
+    for (; from < to; from++, to--) {
         let temp = L.stack[from];
         L.stack[from] = L.stack[to];
         L.stack[to] = temp;
@@ -113,15 +137,16 @@ const reverse = function(L, from, to) {
 const lua_rotate = function(L, idx, n) {
     let t = L.stack[L.top - 1];
     let p = index2addr(L, idx);
+    let pIdx = index2addr_(L, idx);
 
     assert(!p.ttisnil() && idx > lua.LUA_REGISTRYINDEX, "index not in the stack");
     assert((n >= 0 ? n : -n) <= (L.top - idx), "invalid 'n'");
 
-    let m = n >= 0 ? L.top - 1 - n : L.top + idx - n - 1;  /* end of prefix */
+    let m = n >= 0 ? L.top - 1 - n : pIdx - n - 1;  /* end of prefix */
 
-    reverse(L, L.top + idx, m);
+    reverse(L, pIdx, m);
     reverse(L, m + 1, L.top - 1);
-    reverse(L, L.top + idx, L.top - 1);
+    reverse(L, pIdx, L.top - 1);
 };
 
 const lua_remove = function(L, idx) {
@@ -129,6 +154,10 @@ const lua_remove = function(L, idx) {
     lua_pop(L, 1);
 };
 
+const lua_insert = function(L, idx) {
+    lua_rotate(L, idx, 1);
+};
+
 /*
 ** push functions (JS -> stack)
 */
@@ -629,4 +658,5 @@ module.exports.lua_setmetatable    = lua_setmetatable;
 module.exports.lua_settop          = lua_settop;
 module.exports.lua_rawequal        = lua_rawequal;
 module.exports.lua_concat          = lua_concat;
-module.exports.lua_error           = lua_error;
\ No newline at end of file
+module.exports.lua_error           = lua_error;
+module.exports.lua_insert          = lua_insert;
\ No newline at end of file
diff --git a/src/lbaselib.js b/src/lbaselib.js
index 205d57a..ac0ac4c 100644
--- a/src/lbaselib.js
+++ b/src/lbaselib.js
@@ -7,6 +7,7 @@ const lua     = require('./lua.js');
 const lapi    = require('./lapi.js');
 const lauxlib = require('./lauxlib.js');
 const CT      = lua.constant_types;
+const TS      = lua.thread_status;
 
 const luaB_print = function(L) {
     let n = lapi.lua_gettop(L); /* number of arguments */
@@ -99,6 +100,45 @@ const luaB_error = function(L) {
     return lapi.lua_error(L);
 };
 
+/*
+** Continuation function for 'pcall' and 'xpcall'. Both functions
+** already pushed a 'true' before doing the call, so in case of success
+** 'finishpcall' only has to return everything in the stack minus
+** 'extra' values (where 'extra' is exactly the number of items to be
+** ignored).
+*/
+const finishpcall = function(L, status, extra) {
+    if (status !== TS.LUA_OK && status !== TS.LUA_YIELD) {  /* error? */
+        lapi.lua_pushboolean(L, 0);  /* first result (false) */
+        lapi.lua_pushvalue(L, -2);  /* error message */
+        return 2;  /* return false, msg */
+    } else
+        return lapi.lua_gettop(L) - extra;
+};
+
+const luaB_pcall = function(L) {
+    lauxlib.luaL_checkany(L, 1);
+    lapi.lua_pushboolean(L, 1);  /* first result if no errors */
+    lapi.lua_insert(L, 1);  /* put it in place */
+    let status = lapi.lua_pcallk(L, lapi.lua_gettop(L) - 2, lua.LUA_MULTRET, 0, 0, finishpcall);
+    return finishpcall(L, status, 0);
+};
+
+/*
+** Do a protected call with error handling. After 'lua_rotate', the
+** stack will have <f, err, true, f, [args...]>; so, the function passes
+** 2 to 'finishpcall' to skip the 2 first values when returning results.
+*/
+const luaB_xpcall = function(L) {
+    let n = lapi.lua_gettop(L);
+    lauxlib.luaL_checktype(L, 2, CT.LUA_TFUNCTION);
+    lapi.lua_pushboolean(L, 1);
+    lapi.lua_pushvalue(L, 1);
+    lapi.lua_rotate(L, 3, 2);
+    let status = lapi.lua_pcallk(L, n - 2, lua.LUA_MULTRET, 2, 2, finishpcall);
+    return finishpcall(L, status, 2);
+};
+
 const base_funcs = {
     "collectgarbage": function () {},
     "print":          luaB_print,
@@ -109,7 +149,9 @@ const base_funcs = {
     "rawset":         luaB_rawset,
     "rawget":         luaB_rawget,
     "type":           luaB_type,
-    "error":          luaB_error
+    "error":          luaB_error,
+    "pcall":          luaB_pcall,
+    "xpcall":         luaB_xpcall,
 };
 
 const luaopen_base = function(L) {