table.unpack

3 files changed, 57 insertions, 2 deletions

diff --git a/README.md b/README.md
index aafcec2..16d967a 100644
--- a/README.md
+++ b/README.md
@@ -206,11 +206,11 @@
     - [ ] Table
         - [x] table.concat
         - [x] table.pack
+        - [x] table.unpack
         - [ ] table.insert
         - [ ] table.move
         - [ ] table.remove
         - [ ] table.sort
-        - [ ] table.unpack
 - [ ] Debug (errors)
 - [ ] DOM API binding
 - [ ] Parse Lua
diff --git a/src/ltablib.js b/src/ltablib.js
index ec7c578..86b57d7 100644
--- a/src/ltablib.js
+++ b/src/ltablib.js
@@ -91,9 +91,23 @@ const pack = function(L) {
     return 1;  /* return table */
 };
 
+const unpack = function(L) {
+    let i = lauxlib.luaL_optinteger(L, 2, 1);
+    let e = lauxlib.luaL_opt(L, lauxlib.luaL_checkinteger, 3, lapi.lua_len(L, 1));
+    if (i > e) return 0;  /* empty range */
+    let n = e - i;  /* number of elements minus 1 (avoid overflows) */
+    if (n >= Number.MAX_SAFE_INTEGER || !lapi.lua_checkstack(L, ++n))
+        return lauxlib.luaL_error(L, "too many results to unpack");
+    for (; i < e; i++)  /* push arg[i..e - 1] (to avoid overflows) */
+        lapi.lua_geti(L, 1, i);
+    lapi.lua_geti(L, 1, e);  /* push last element */
+    return n;
+};
+
 const tab_funcs = {
     "concat": tconcat,
-    "pack":   pack
+    "pack":   pack,
+    "unpack": unpack,
 };
 
 const luaopen_table = function(L) {
diff --git a/tests/ltablib.js b/tests/ltablib.js
index 28b9ce0..8221fe0 100644
--- a/tests/ltablib.js
+++ b/tests/ltablib.js
@@ -75,4 +75,45 @@ test('table.pack', function (t) {
         [1, 2, 3],
         "Correct element(s) on the stack"
     );
+});
+
+
+test('table.unpack', function (t) {
+    let luaCode = `
+        return table.unpack({1, 2, 3, 4, 5}, 2, 4)
+    `, L;
+    
+    t.plan(4);
+
+    t.doesNotThrow(function () {
+
+        let bc = toByteCode(luaCode).dataView;
+
+        L = lauxlib.luaL_newstate();
+
+        linit.luaL_openlibs(L);
+
+        lapi.lua_load(L, bc, "test-table.unpack");
+
+        lapi.lua_call(L, 0, -1);
+
+    }, "JS Lua program ran without error");
+
+    t.strictEqual(
+        lapi.lua_tointeger(L, -3),
+        2,
+        "Correct element(s) on the stack"
+    );
+
+    t.strictEqual(
+        lapi.lua_tointeger(L, -2),
+        3,
+        "Correct element(s) on the stack"
+    );
+
+    t.strictEqual(
+        lapi.lua_tointeger(L, -1),
+        4,
+        "Correct element(s) on the stack"
+    );
 });
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