/*
* DEEP.CPP Copyright (c) 2024, Benoit Germain
*
* Deep userdata support, separate in its own source file to help integration
* without enforcing a Lanes dependency
*/
/*
===============================================================================
Copyright (C) 2002-10 Asko Kauppi <akauppi@gmail.com>
2011-24 Benoit Germain <bnt.germain@gmail.com>
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
===============================================================================
*/
#include "deep.h"
#include "tools.h"
#include <bit>
#include <cassert>
/*-- Metatable copying --*/
/*---=== Deep userdata ===---*/
/*
* 'registry[REGKEY]' is a two-way lookup table for 'factory's and those type's
* metatables:
*
* metatable -> factory
* factory -> metatable
*/
// xxh64 of string "kDeepLookupRegKey" generated at https://www.pelock.com/products/hash-calculator
static constexpr RegistryUniqueKey kDeepLookupRegKey{ 0xC6788345703C6059ull };
/*
* The deep proxy cache is a weak valued table listing all deep UD proxies indexed by the deep UD that they are proxying
* xxh64 of string "kDeepProxyCacheRegKey" generated at https://www.pelock.com/products/hash-calculator
*/
static constexpr RegistryUniqueKey kDeepProxyCacheRegKey{ 0xEBCD49AE1A3DD35Eull };
// #################################################################################################
/*
* Sets up [-1]<->[-2] two-way lookups, and ensures the lookup table exists.
* Pops the both values off the stack.
*/
void DeepFactory::storeDeepLookup(lua_State* L_) const
{
// the deep metatable is at the top of the stack // L_: mt
STACK_GROW(L_, 3);
STACK_CHECK_START_REL(L_, 0); // L_: mt
std::ignore = kDeepLookupRegKey.getSubTable(L_, 0, 0); // L_: mt {}
lua_pushvalue(L_, -2); // L_: mt {} mt
lua_pushlightuserdata(L_, std::bit_cast<void*>(this)); // L_: mt {} mt factory
lua_rawset(L_, -3); // L_: mt {}
STACK_CHECK(L_, 1);
lua_pushlightuserdata(L_, std::bit_cast<void*>(this)); // L_: mt {} factory
lua_pushvalue(L_, -3); // L_: mt {} factory mt
lua_rawset(L_, -3); // L_: mt {}
STACK_CHECK(L_, 1);
lua_pop(L_, 1); // L_: mt
STACK_CHECK(L_, 0);
}
// #################################################################################################
// Pops the key (metatable or factory) off the stack, and replaces with the deep lookup value (factory/metatable/nil).
static void LookupDeep(lua_State* L_)
{
STACK_GROW(L_, 1);
STACK_CHECK_START_REL(L_, 1); // L_: a
kDeepLookupRegKey.pushValue(L_); // L_: a {}
if (!lua_isnil(L_, -1)) {
lua_insert(L_, -2); // L_: {} a
lua_rawget(L_, -2); // L_: {} b
}
lua_remove(L_, -2); // L_: a|b
STACK_CHECK(L_, 1);
}
// #################################################################################################
// Return the registered factory for 'index' (deep userdata proxy), or nullptr if 'index' is not a deep userdata proxy.
[[nodiscard]] DeepFactory* LookupFactory(lua_State* L_, int index_, LookupMode mode_)
{
// when looking inside a keeper, we are 100% sure the object is a deep userdata
if (mode_ == LookupMode::FromKeeper) {
DeepPrelude* const _proxy{ *lua_tofulluserdata<DeepPrelude*>(L_, index_) };
// we can (and must) cast and fetch the internally stored factory
return &_proxy->factory;
} else {
// essentially we are making sure that the metatable of the object we want to copy is stored in our metatable/factory database
// it is the only way to ensure that the userdata is indeed a deep userdata!
// of course, we could just trust the caller, but we won't
STACK_GROW(L_, 1);
STACK_CHECK_START_REL(L_, 0);
if (!lua_getmetatable(L_, index_)) { // L_: deep ... metatable?
return nullptr; // no metatable: can't be a deep userdata object!
}
// replace metatable with the factory pointer, if it is actually a deep userdata
LookupDeep(L_); // L_: deep ... factory|nil
DeepFactory* const _ret{ lua_tolightuserdata<DeepFactory>(L_, -1) }; // nullptr if not a userdata
lua_pop(L_, 1);
STACK_CHECK(L_, 0);
return _ret;
}
}
// #################################################################################################
void DeepFactory::DeleteDeepObject(lua_State* L_, DeepPrelude* o_)
{
STACK_CHECK_START_REL(L_, 0);
o_->factory.deleteDeepObjectInternal(L_, o_);
STACK_CHECK(L_, 0);
}
// #################################################################################################
/*
* void= mt.__gc( proxy_ud )
*
* End of life for a proxy object; reduce the deep reference count and clean it up if reaches 0.
*
*/
[[nodiscard]] static int deep_userdata_gc(lua_State* L_)
{
DeepPrelude* const* const _proxy{ lua_tofulluserdata<DeepPrelude*>(L_, 1) };
DeepPrelude* const _p{ *_proxy };
// can work without a universe if creating a deep userdata from some external C module when Lanes isn't loaded
// in that case, we are not multithreaded and locking isn't necessary anyway
bool const isLastRef{ _p->refcount.fetch_sub(1, std::memory_order_relaxed) == 1 };
if (isLastRef) {
// retrieve wrapped __gc
lua_pushvalue(L_, lua_upvalueindex(1)); // L_: self __gc?
if (!lua_isnil(L_, -1)) {
lua_insert(L_, -2); // L_: __gc self
lua_call(L_, 1, 0); // L_:
} else {
// need an empty stack in case we are GC_ing from a Keeper, so that empty stack checks aren't triggered
lua_pop(L_, 2); // L_:
}
DeepFactory::DeleteDeepObject(L_, _p);
}
return 0;
}
// #################################################################################################
// TODO: convert to UniqueKey::getSubTableMode
static void push_registry_subtable_mode(lua_State* L_, RegistryUniqueKey key_, const char* mode_)
{
STACK_GROW(L_, 4);
STACK_CHECK_START_REL(L_, 0);
if (!key_.getSubTable(L_, 0, 0)) { // L_: {}
// Set its metatable if requested
if (mode_) {
lua_createtable(L_, 0, 1); // L_: {} mt
lua_pushliteral(L_, "__mode"); // L_: {} mt "__mode"
lua_pushstring(L_, mode_); // L_: {} mt "__mode" mode
lua_rawset(L_, -3); // L_: {} mt
lua_setmetatable(L_, -2); // L_: {}
}
}
STACK_CHECK(L_, 1);
}
// #################################################################################################
/*
* Push a proxy userdata on the stack.
* returns nullptr if ok, else some error string related to bad factory behavior or module require problem
* (error cannot happen with mode_ == LookupMode::ToKeeper)
*
* Initializes necessary structures if it's the first time 'factory' is being
* used in this Lua state (metatable, registring it). Otherwise, increments the
* reference count.
*/
char const* DeepFactory::PushDeepProxy(DestState L_, DeepPrelude* prelude_, int nuv_, LookupMode mode_)
{
// Check if a proxy already exists
push_registry_subtable_mode(L_, kDeepProxyCacheRegKey, "v"); // L_: DPC
lua_pushlightuserdata(L_, prelude_); // L_: DPC deep
lua_rawget(L_, -2); // L_: DPC proxy
if (!lua_isnil(L_, -1)) {
lua_remove(L_, -2); // L_: proxy
return nullptr;
} else {
lua_pop(L_, 1); // L_: DPC
}
STACK_GROW(L_, 7);
STACK_CHECK_START_REL(L_, 0);
// a new full userdata, fitted with the specified number of uservalue slots (always 1 for Lua < 5.4)
DeepPrelude** const _proxy{ lua_newuserdatauv<DeepPrelude*>(L_, nuv_) }; // L_: DPC proxy
LUA_ASSERT(L_, _proxy);
*_proxy = prelude_;
prelude_->refcount.fetch_add(1, std::memory_order_relaxed); // one more proxy pointing to this deep data
// Get/create metatable for 'factory' (in this state)
DeepFactory& factory = prelude_->factory;
lua_pushlightuserdata(L_, std::bit_cast<void*>(&factory)); // L_: DPC proxy factory
LookupDeep(L_); // L_: DPC proxy metatable|nil
if (lua_isnil(L_, -1)) { // No metatable yet.
lua_pop(L_, 1); // L_: DPC proxy
int const _oldtop{ lua_gettop(L_) };
// 1 - make one and register it
if (mode_ != LookupMode::ToKeeper) {
factory.createMetatable(L_); // L_: DPC proxy metatable
if (lua_gettop(L_) - _oldtop != 1 || !lua_istable(L_, -1)) {
// factory didn't push exactly 1 value, or the value it pushed is not a table: ERROR!
lua_settop(L_, _oldtop); // L_: DPC proxy X
lua_pop(L_, 3); // L_:
return "Bad DeepFactory::createMetatable overload: unexpected pushed value";
}
// if the metatable contains a __gc, we will call it from our own
lua_getfield(L_, -1, "__gc"); // L_: DPC proxy metatable __gc
} else {
// keepers need a minimal metatable that only contains our own __gc
lua_createtable(L_, 0, 1); // L_: DPC proxy metatable
lua_pushnil(L_); // L_: DPC proxy metatable nil
}
if (lua_isnil(L_, -1)) {
// Add our own '__gc' method
lua_pop(L_, 1); // L_: DPC proxy metatable
lua_pushcfunction(L_, deep_userdata_gc); // L_: DPC proxy metatable deep_userdata_gc
} else {
// Add our own '__gc' method wrapping the original
lua_pushcclosure(L_, deep_userdata_gc, 1); // DPC proxy metatable deep_userdata_gc
}
lua_setfield(L_, -2, "__gc"); // L_: DPC proxy metatable
// Memorize for later rounds
factory.storeDeepLookup(L_);
// 2 - cause the target state to require the module that exported the factory
if (char const* const _modname{ factory.moduleName() }; _modname) { // we actually got a module name
// L.registry._LOADED exists without having registered the 'package' library.
lua_getglobal(L_, "require"); // DPC proxy metatable require()
// check that the module is already loaded (or being loaded, we are happy either way)
if (lua_isfunction(L_, -1)) {
lua_pushstring(L_, _modname); // L_: DPC proxy metatable require() "module"
lua_getfield(L_, LUA_REGISTRYINDEX, LUA_LOADED_TABLE); // L_: DPC proxy metatable require() "module" _R._LOADED
if (lua_istable(L_, -1)) {
lua_pushvalue(L_, -2); // L_: DPC proxy metatable require() "module" _R._LOADED "module"
lua_rawget(L_, -2); // L_: DPC proxy metatable require() "module" _R._LOADED module
int const alreadyloaded = lua_toboolean(L_, -1);
if (!alreadyloaded) { // not loaded
int require_result;
lua_pop(L_, 2); // L_: DPC proxy metatable require() "module"
// require "modname"
require_result = lua_pcall(L_, 1, 0, 0); // L_: DPC proxy metatable error?
if (require_result != LUA_OK) {
// failed, return the error message
lua_pushfstring(L_, "error while requiring '%s' identified by DeepFactory::moduleName: ", _modname);
lua_insert(L_, -2); // L_: DPC proxy metatable prefix error
lua_concat(L_, 2); // L_: DPC proxy metatable error
return lua_tostring(L_, -1);
}
} else { // already loaded, we are happy
lua_pop(L_, 4); // L_: DPC proxy metatable
}
} else { // no L.registry._LOADED; can this ever happen?
lua_pop(L_, 6); // L_:
return "unexpected error while requiring a module identified by DeepFactory::moduleName";
}
} else { // a module name, but no require() function :-(
lua_pop(L_, 4); // L_:
return "lanes receiving deep userdata should register the 'package' library";
}
}
}
STACK_CHECK(L_, 2); // DPC proxy metatable
LUA_ASSERT(L_, lua_type_as_enum(L_, -2) == LuaType::USERDATA);
LUA_ASSERT(L_, lua_istable(L_, -1));
lua_setmetatable(L_, -2); // DPC proxy
// If we're here, we obviously had to create a new proxy, so cache it.
lua_pushlightuserdata(L_, prelude_); // L_: DPC proxy deep
lua_pushvalue(L_, -2); // L_: DPC proxy deep proxy
lua_rawset(L_, -4); // L_: DPC proxy
lua_remove(L_, -2); // L_: proxy
LUA_ASSERT(L_, lua_type_as_enum(L_, -1) == LuaType::USERDATA);
STACK_CHECK(L_, 0);
return nullptr;
}
// #################################################################################################
/*
* Create a deep userdata
*
* proxy_ud= deep_userdata( [...] )
*
* Creates a deep userdata entry of the type defined by the factory.
* Parameters found on the stack are left as is and passed on to DeepFactory::newDeepObjectInternal.
*
* Reference counting and true userdata proxying are taken care of for the actual data type.
*
* Types using the deep userdata system (and only those!) can be passed between
* separate Lua states via 'luaG_inter_move()'.
*
* Returns: 'proxy' userdata for accessing the deep data via 'DeepFactory::toDeep()'
*/
int DeepFactory::pushDeepUserdata(DestState L_, int nuv_) const
{
STACK_GROW(L_, 1);
STACK_CHECK_START_REL(L_, 0);
int const _oldtop{ lua_gettop(L_) };
DeepPrelude* const _prelude{ newDeepObjectInternal(L_) };
if (_prelude == nullptr) {
raise_luaL_error(L_, "DeepFactory::newDeepObjectInternal failed to create deep userdata (out of memory)");
}
if (_prelude->magic != kDeepVersion) {
// just in case, don't leak the newly allocated deep userdata object
deleteDeepObjectInternal(L_, _prelude);
raise_luaL_error(L_, "Bad Deep Factory: kDeepVersion is incorrect, rebuild your implementation with the latest deep implementation");
}
LUA_ASSERT(L_, _prelude->refcount.load(std::memory_order_relaxed) == 0); // 'DeepFactory::PushDeepProxy' will lift it to 1
LUA_ASSERT(L_, &_prelude->factory == this);
if (lua_gettop(L_) - _oldtop != 0) {
// just in case, don't leak the newly allocated deep userdata object
deleteDeepObjectInternal(L_, _prelude);
raise_luaL_error(L_, "Bad DeepFactory::newDeepObjectInternal overload: should not push anything on the stack");
}
char const* const _err{ DeepFactory::PushDeepProxy(L_, _prelude, nuv_, LookupMode::LaneBody) }; // proxy
if (_err != nullptr) {
raise_luaL_error(L_, _err);
}
STACK_CHECK(L_, 1);
return 1;
}
// #################################################################################################
/*
* Access deep userdata through a proxy.
*
* Reference count is not changed, and access to the deep userdata is not
* serialized. It is the module's responsibility to prevent conflicting usage.
*/
DeepPrelude* DeepFactory::toDeep(lua_State* L_, int index_) const
{
STACK_CHECK_START_REL(L_, 0);
// ensure it is actually a deep userdata we created
if (LookupFactory(L_, index_, LookupMode::LaneBody) != this) {
return nullptr; // no metatable, or wrong kind
}
STACK_CHECK(L_, 0);
DeepPrelude** const _proxy{ lua_tofulluserdata<DeepPrelude*>(L_, index_) };
return *_proxy;
}