+/**
+ * @brief Writes the specified data into a memory buffer.
+ *
+ * This function is a valid lua_Writer that writes into a memory buffer passed
+ * as userdata.
+ *
+ * @param L a lua state
+ * @param source some data
+ * @param sz number of bytes of data
+ * @param user_data the memory buffer to write
+ */
+static int writer(lua_State* L, const void* source, size_t size, void* userdata) {
+
+ buffer_t buffer = (buffer_t) userdata;
+ while (buffer->capacity < buffer->size + size) {
+ buffer->capacity *= 2;
+ buffer->data = xbt_realloc(buffer->data, buffer->capacity);
+ }
+ memcpy(buffer->data + buffer->size, source, size);
+ buffer->size += size;
+
+ return 0;
+}
+
+/**
+ * @brief Pops a value from the stack of a source state and pushes it on the
+ * stack of another state.
+ *
+ * If the value is a table, its content is copied recursively. To avoid cycles,
+ * a table of previsously visited tables must be present at index 1 of dst.
+ * Its keys are pointers to visited tables in src and its values are the tables
+ * already built.
+ *
+ * TODO: add support of upvalues
+ *
+ * @param src the source state
+ * @param dst the destination state
+ * @param name a name describing the value
+ */
+static void move_value(lua_State* dst, lua_State *src, const char* name) {
+
+ luaL_checkany(src, -1); /* check the value to copy */
+ luaL_checktype(dst, 1, LUA_TTABLE); /* check the presence of a table of
+ previously visited tables */
+
+ XBT_DEBUG("Copying value %s", name);
+
+ stack_dump("src before copying a value (should be ... value): ", src);
+ stack_dump("dst before copying a value (should be visited ...): ", dst);
+
+ switch (lua_type(src, -1)) {
+
+ case LUA_TNIL:
+ lua_pushnil(dst);
+ break;
+
+ case LUA_TNUMBER:
+ lua_pushnumber(dst, lua_tonumber(src, -1));
+ break;
+
+ case LUA_TBOOLEAN:
+ lua_pushboolean(dst, lua_toboolean(src, -1));
+ break;
+
+ case LUA_TSTRING:
+ /* no worries about memory: lua_pushstring makes a copy */
+ lua_pushstring(dst, lua_tostring(src, -1));
+ break;
+
+ case LUA_TFUNCTION:
+ /* it's a function that does not exist yet in L2 */
+
+ if (lua_iscfunction(src, -1)) {
+ /* it's a C function: just copy the pointer */
+ XBT_DEBUG("Copying C function '%s'", name);
+ lua_CFunction f = lua_tocfunction(src, -1);
+ lua_pushcfunction(dst, f);
+ }
+ else {
+ /* it's a Lua function: dump it from src */
+ XBT_DEBUG("Dumping Lua function '%s'", name);
+
+ s_buffer_t buffer;
+ buffer.capacity = 64;
+ buffer.size = 0;
+ buffer.data = xbt_new(char, buffer.capacity);
+
+ /* copy the binary chunk from src into a buffer */
+ int error = lua_dump(src, writer, &buffer);
+ xbt_assert(!error, "Failed to dump function '%s' from the source state: error %d",
+ name, error);
+
+ /* load the chunk into dst */
+ error = luaL_loadbuffer(dst, buffer.data, buffer.size, name);
+ xbt_assert(!error, "Failed to load function '%s' from the source state: %s",
+ name, lua_tostring(dst, -1));
+ XBT_DEBUG("Function '%s' successfully dumped from source state.", name);
+ }
+ break;
+
+ case LUA_TTABLE:
+
+ /* see if this table was already visited */
+ lua_pushlightuserdata(dst, (void*) lua_topointer(src, -1));
+ /* dst: visited ... psrctable */
+ lua_gettable(dst, 1);
+ /* dst: visited ... table/nil */
+ if (lua_istable(dst, -1)) {
+ XBT_DEBUG("Nothing to do: table already visited");
+ /* dst: visited ... table */
+ }
+ else {
+ XBT_DEBUG("First visit of this table");
+ /* dst: visited ... nil */
+ lua_pop(dst, 1);
+ /* dst: visited ... */
+
+ /* first visit: create the new table in dst */
+ lua_newtable(dst);
+ /* dst: visited ... table */
+
+ /* mark the table as visited to avoid infinite recursion */
+ lua_pushlightuserdata(dst, (void*) lua_topointer(src, -1));
+ /* dst: visited ... table psrctable */
+ lua_pushvalue(dst, -2);
+ /* dst: visited ... table psrctable table */
+ lua_settable(dst, 1);
+ /* dst: visited ... table */
+ XBT_DEBUG("Table marked as visited");
+
+ stack_dump("dst after marking the table as visited (should be visited ... table): ", dst);
+
+ /* copy the metatable if any */
+ int has_meta_table = lua_getmetatable(src, -1);
+ /* src: ... table mt? */
+ if (has_meta_table) {
+ XBT_DEBUG("Copying metatable");
+ /* src: ... table mt */
+ move_value(dst, src, "metatable");
+ /* src: ... table
+ dst: visited ... table mt */
+ lua_setmetatable(dst, -2);
+ /* dst: visited ... table */
+ }
+ else {
+ XBT_DEBUG("No metatable");
+ }
+
+ stack_dump("src before traversing the table (should be ... table): ", src);
+ stack_dump("dst before traversing the table (should be visited ... table): ", dst);
+
+ /* traverse the table of src and copy each element */
+ lua_pushnil(src);
+ /* src: ... table nil */
+ while (lua_next(src, -2) != 0) {
+ /* src: ... table key value */
+
+ XBT_DEBUG("Copying table element %s", keyvalue_tostring(src, -2, -1));
+
+ stack_dump("src before copying table element (should be ... table key value): ", src);
+ stack_dump("dst before copying table element (should be visited ... table): ", dst);
+
+ /* copy the key */
+ lua_pushvalue(src, -2);
+ /* src: ... table key value key */
+ XBT_DEBUG("Copying the element key");
+ move_value(dst, src, value_tostring(src, -1));
+ /* src: ... table key value
+ dst: visited ... table key */
+ XBT_DEBUG("Copied the element key");
+
+ /* copy the value */
+ XBT_DEBUG("Copying the element value");
+ move_value(dst, src, value_tostring(src, -1));
+ /* src: ... table key
+ dst: visited ... table key value */
+ XBT_DEBUG("Copied the element value");
+
+ /* set the table element */
+ lua_settable(dst, -3);
+ /* dst: visited ... table */
+
+ /* the key stays on top of src for next iteration */
+ stack_dump("src before next iteration (should be ... table key): ", src);
+ stack_dump("dst before next iteration (should be visited ... table): ", dst);
+ }
+ XBT_DEBUG("Finished traversing the table");
+ }
+ break;
+
+ case LUA_TLIGHTUSERDATA:
+ lua_pushlightuserdata(dst, lua_touserdata(src, -1));
+ break;
+
+ case LUA_TUSERDATA:
+ XBT_WARN("Cannot copy a full userdata from the source state.");
+ lua_pushnil(dst);
+ break;
+
+ case LUA_TTHREAD:
+ XBT_WARN("Cannot copy a thread from the source state.");
+ lua_pushnil(dst);
+ break;
+ }
+
+ /* pop the value from src */
+ lua_pop(src, 1);
+
+ stack_dump("src after copying a value (should be ...): ", src);
+ stack_dump("dst after copying a value (should be visited ... value): ", dst);