add support define metamethods for record

Signed-off-by: Jianhui Zhao <[email protected]>

ffi.c

@@ -82,6 +82,11 @@ enum {
     CTYPE_FUNC,
 };
 
+enum {
+    METATYPE_FLAG_INDEX    = 1 << 0,
+    METATYPE_FLAG_TOSTRING = 1 << 1
+};
+
 struct crecord;
 struct carray;
 struct cfunc;
@@ -112,6 +117,8 @@ struct crecord_field {
 
 struct crecord {
     ffi_type ft;
+    int mt_ref;
+    uint8_t mflags;
     uint8_t nfield:5;
     uint8_t is_union:1;
     uint8_t anonymous:1;
@@ -622,6 +629,16 @@ static int __cdata_tostring(lua_State *L, struct cdata *cd)
 static int cdata_tostring(lua_State *L)
 {
     struct cdata *cd = luaL_checkudata(L, 1, CDATA_MT);
+    struct ctype *ct = cd->ct;
+
+    if (ct->type == CTYPE_RECORD && ct->rc->mflags & METATYPE_FLAG_TOSTRING) {
+        lua_rawgeti(L, LUA_REGISTRYINDEX, ct->rc->mt_ref);
+        lua_getfield(L, -1, "__tostring");
+        lua_pushvalue(L, 1);
+        lua_call(L, 1, 1);
+        return 1;
+    }
+
     return __cdata_tostring(L, cd);
 }
 
@@ -1016,6 +1033,7 @@ static struct crecord_field *cdata_crecord_find_field(
 static int cdata_index_crecord(lua_State *L, struct cdata *cd, struct ctype *ct, bool to)
 {
     void *ptr = cdata_type(cd) == CTYPE_PTR ? cdata_ptr_ptr(cd) : cdata_ptr(cd);
+    struct crecord *rc = ct->rc;
     struct crecord_field *field;
     size_t offset = 0;
     const char *name;
@@ -1035,8 +1053,24 @@ static int cdata_index_crecord(lua_State *L, struct cdata *cd, struct ctype *ct,
         lua_pop(L, 2);
     }
 
-    field = cdata_crecord_find_field(ct->rc->fields, ct->rc->nfield, name, &offset);
+    field = cdata_crecord_find_field(rc->fields, rc->nfield, name, &offset);
     if (!field) {
+        if (to) {
+            if (rc->mflags & METATYPE_FLAG_INDEX) {
+                lua_rawgeti(L, LUA_REGISTRYINDEX, rc->mt_ref);
+                lua_getfield(L, -1, "__index");
+
+                if (lua_isfunction(L, -1))
+                    return 1;
+
+                if (lua_istable(L, -1)) {
+                    lua_getfield(L, -1, name);
+                    if (!lua_isnil(L, -1))
+                        return 1;
+                }
+            }
+        }
+
         __ctype_tostring(L, ct);
         return luaL_error(L, "ctype '%s' has no member named '%s'", lua_tostring(L, -1), name);
     }
@@ -1307,6 +1341,10 @@ static int ctype_gc(lua_State *L)
         int i;
         for (i = 0; i < ct->rc->nfield; i++)
             free(ct->rc->fields[i]);
+
+        if (ct->rc->mt_ref != LUA_REFNIL)
+            luaL_unref(L, LUA_REGISTRYINDEX, ct->rc->mt_ref);
+
         free(ct->rc);
     }
 
@@ -1615,6 +1653,8 @@ static int cparse_record(lua_State *L, struct ctype *ct, bool is_union)
         if (!ct->rc)
             return luaL_error(L, "no mem");
 
+        ct->rc->mt_ref = LUA_REFNIL;
+
         memcpy(ct->rc->fields, fields, sizeof(struct crecord_field *) * nfield);
 
         if (named) {
@@ -2157,6 +2197,42 @@ static int lua_ffi_cast(lua_State *L)
     return 1;
 }
 
+static int lua_ffi_metatype(lua_State *L)
+{
+    struct ctype *ct = luaL_checkudata(L, 1, CTYPE_MT);
+    struct crecord *rc = ct->rc;
+    uint8_t mflags = 0;
+
+    luaL_argcheck(L, ct->type == CTYPE_RECORD, 1, "invalid C type");
+
+    luaL_checktype(L, 2, LUA_TTABLE);
+
+#define FIELD_CHECK(name, flag) { \
+            lua_getfield(L, 2, "__" name); \
+            if (!lua_isnil(L, -1)) { \
+                mflags |= METATYPE_FLAG_##flag; \
+            } \
+            lua_pop(L, 1); \
+        }
+
+    FIELD_CHECK("index", INDEX);
+    FIELD_CHECK("tostring", TOSTRING);
+
+#undef FIELD_CHECK
+
+    rc->mflags = mflags;
+
+    if (rc->mt_ref != LUA_REFNIL)
+        luaL_unref(L, LUA_REGISTRYINDEX, rc->mt_ref);
+
+    lua_pushvalue(L, 2);
+    rc->mt_ref = luaL_ref(L, LUA_REGISTRYINDEX);
+
+    lua_settop(L, 1);
+
+    return 1;
+}
+
 static int lua_ffi_typeof(lua_State *L)
 {
     lua_check_ct(L, NULL, true);
@@ -2356,6 +2432,7 @@ static const luaL_Reg methods[] = {
 
     {"new", lua_ffi_new},
     {"cast", lua_ffi_cast},
+    {"metatype", lua_ffi_metatype},
     {"typeof", lua_ffi_typeof},
     {"addressof", lua_ffi_addressof},
     {"gc", lua_ffi_gc},

tests/test.lua

@@ -151,6 +151,25 @@ local tests = {
 
         p[1] = 567
         assert(a[1] == 567)
+    end,
+    function()
+        local tp = ffi.metatype(ffi.typeof('struct Point'), {
+            __tostring = function(self)
+                return string.format('x:%d,y:%d', self.x, self.y)
+            end,
+            __index = {
+                add = function(self, x, y)
+                    self.x = self.x + x
+                    self.y = self.y + y
+                end
+            }
+        })
+
+        local p = ffi.new(tp, {45, 67})
+        assert(tostring(p) == 'x:45,y:67')
+
+        p:add(1, 1)
+        assert(p.x == 46 and p.y == 68)
     end
 }