From 533523c45540ab5ffe233bed58824ca8f30890ce Mon Sep 17 00:00:00 2001
From: Benoit Giannangeli <benoit.giannangeli@boursorama.fr>
Date: Wed, 15 Feb 2017 08:12:58 +0100
Subject: __len

---
 README.md    | 12 ++++++------
 src/lvm.js   |  4 ++--
 tests/ltm.js | 59 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 67 insertions(+), 8 deletions(-)

diff --git a/README.md b/README.md
index 9505854..7a6e972 100644
--- a/README.md
+++ b/README.md
@@ -8,20 +8,17 @@
 - [ ] Basic types representation:
     - [x] nil
     - [x] boolean
+    - [x] table
+    - [x] function
+    - [ ] string (8-bit clean)
     - [ ] number (32-bit ?)
         - [ ] integer
         - [ ] float
-    - [ ] string (8-bit clean)
-    - [ ] table
-    - [ ] function
     - [ ] userdata
     - [ ] thread
 - [ ] Tag Methods
     - [x] `__index`
     - [x] `__newindex`
-    - [x] `__gc` (unavailable)
-    - [x] `__mode` (unavailable)
-    - [ ] `__len`
     - [x] `__add`
     - [x] `__sub`
     - [x] `__mul`
@@ -39,6 +36,9 @@
     - [x] `__eq`
     - [x] `__lt`
     - [x] `__le`
+    - [x] `__gc` (unavailable)
+    - [x] `__mode` (unavailable)
+    - [x] `__len`
     - [ ] `__concat`
     - [ ] `__call`
     - [ ] `__tostring`
diff --git a/src/lvm.js b/src/lvm.js
index 815ca2f..07a9f96 100644
--- a/src/lvm.js
+++ b/src/lvm.js
@@ -854,8 +854,8 @@ const luaV_objlen = function(L, ra, rb) {
     let tm;
     switch(rb.ttype()) {
         case CT.LUA_TTABLE: {
-            tm = rb.value.metatable;
-            if (tm) break;
+            tm = ltm.luaT_gettmbyobj(L, rb, TMS.TM_LEN);
+            if (!tm.ttisnil()) break;
             L.stack[ra] = rb.luaH_getn();
             return;
         }
diff --git a/tests/ltm.js b/tests/ltm.js
index 8a20f67..00ea0e6 100644
--- a/tests/ltm.js
+++ b/tests/ltm.js
@@ -1137,4 +1137,63 @@ test('__unm, __bnot', function (t) {
         "hello",
         "Program output is correct"
     );
+});
+
+
+test('__len', function (t) {
+    let luaCode = `
+        local mt = {
+            __len = function (a)
+                return "hello"
+            end
+        }
+
+        local t = {}
+
+        -- setmetatable(t, mt)
+
+        return #t
+    `, L;
+    
+    t.plan(4);
+
+    t.comment("Running following code: \n" + luaCode);
+
+    // main <hello.lua:0,0> (7 instructions at 0x7f91f0600ac0)
+    // 0+ params, 3 slots, 1 upvalue, 2 locals, 1 constant, 1 function
+    //         1       [1]     NEWTABLE        0 0 1
+    //         2       [4]     CLOSURE         1 0     ; 0x7f91f0600d10
+    //         3       [4]     SETTABLE        0 -1 1  ; "__len" -
+    //         4       [7]     NEWTABLE        1 0 0
+    //         5       [11]    LEN             2 1                      <=== We stop here
+    //         6       [11]    RETURN          2 2
+    //         7       [11]    RETURN          0 1
+    //
+    // ...
+
+    t.doesNotThrow(function () {
+        L = getState(luaCode);
+    }, "Bytecode parsed without errors");
+
+    L.stack[0].p.code[4].breakpoint = true;
+
+    t.doesNotThrow(function () {
+        ldo.luaD_call(L, 0, -1);
+    }, "First part of the program executed without errors");
+
+    L.ci.pcOff--;
+    L.stack[0].p.code[4].breakpoint = false;
+
+    t.comment("We manually set t's metatable to mt");
+    L.stack[2].metatable = L.stack[1];
+
+    t.doesNotThrow(function () {
+        VM.luaV_execute(L);
+    }, "Second part of the program executed without errors");
+
+    t.strictEqual(
+        L.stack[L.top - 1].value,
+        "hello",
+        "Program output is correct"
+    );
 });
\ No newline at end of file
-- 
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