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mlua/src/util.rs
Alex Orlenko fa99f62a99
Fix __index and __newindex wrappers for Luau
2022-03-21 01:08:40 +00:00

992 lines
35 KiB
Rust
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use std::any::{Any, TypeId};
use std::ffi::CStr;
use std::fmt::Write;
use std::os::raw::{c_char, c_int, c_void};
use std::panic::{catch_unwind, resume_unwind, AssertUnwindSafe};
use std::sync::Arc;
use std::{mem, ptr, slice};
use once_cell::sync::Lazy;
use rustc_hash::FxHashMap;
use crate::error::{Error, Result};
use crate::ffi;
static METATABLE_CACHE: Lazy<FxHashMap<TypeId, u8>> = Lazy::new(|| {
let mut map = FxHashMap::with_capacity_and_hasher(32, Default::default());
crate::lua::init_metatable_cache(&mut map);
map.insert(TypeId::of::<WrappedFailure>(), 0);
map.insert(TypeId::of::<String>(), 0);
map
});
// Checks that Lua has enough free stack space for future stack operations. On failure, this will
// panic with an internal error message.
#[inline]
pub unsafe fn assert_stack(state: *mut ffi::lua_State, amount: c_int) {
// TODO: This should only be triggered when there is a logic error in `mlua`. In the future,
// when there is a way to be confident about stack safety and test it, this could be enabled
// only when `cfg!(debug_assertions)` is true.
mlua_assert!(
ffi::lua_checkstack(state, amount) != 0,
"out of stack space"
);
}
// Checks that Lua has enough free stack space and returns `Error::StackError` on failure.
#[inline]
pub unsafe fn check_stack(state: *mut ffi::lua_State, amount: c_int) -> Result<()> {
if ffi::lua_checkstack(state, amount) == 0 {
Err(Error::StackError)
} else {
Ok(())
}
}
pub struct StackGuard {
state: *mut ffi::lua_State,
top: c_int,
extra: c_int,
}
impl StackGuard {
// Creates a StackGuard instance with record of the stack size, and on Drop will check the
// stack size and drop any extra elements. If the stack size at the end is *smaller* than at
// the beginning, this is considered a fatal logic error and will result in a panic.
#[inline]
pub unsafe fn new(state: *mut ffi::lua_State) -> StackGuard {
StackGuard {
state,
top: ffi::lua_gettop(state),
extra: 0,
}
}
// Similar to `new`, but checks and keeps `extra` elements from top of the stack on Drop.
#[inline]
pub unsafe fn new_extra(state: *mut ffi::lua_State, extra: c_int) -> StackGuard {
StackGuard {
state,
top: ffi::lua_gettop(state),
extra,
}
}
}
impl Drop for StackGuard {
fn drop(&mut self) {
unsafe {
let top = ffi::lua_gettop(self.state);
if top < self.top + self.extra {
mlua_panic!("{} too many stack values popped", self.top - top)
}
if top > self.top + self.extra {
if self.extra > 0 {
ffi::lua_rotate(self.state, self.top + 1, self.extra);
}
ffi::lua_settop(self.state, self.top + self.extra);
}
}
}
}
// Call a function that calls into the Lua API and may trigger a Lua error (longjmp) in a safe way.
// Wraps the inner function in a call to `lua_pcall`, so the inner function only has access to a
// limited lua stack. `nargs` is the same as the the parameter to `lua_pcall`, and `nresults` is
// always `LUA_MULTRET`. Provided function must *not* panic, and since it will generally be lonjmping,
// should not contain any values that implements Drop.
// Internally uses 2 extra stack spaces, and does not call checkstack.
pub unsafe fn protect_lua_call(
state: *mut ffi::lua_State,
nargs: c_int,
f: unsafe extern "C" fn(*mut ffi::lua_State) -> c_int,
) -> Result<()> {
let stack_start = ffi::lua_gettop(state) - nargs;
ffi::lua_pushcfunction(state, error_traceback);
ffi::lua_pushcfunction(state, f);
if nargs > 0 {
ffi::lua_rotate(state, stack_start + 1, 2);
}
let ret = ffi::lua_pcall(state, nargs, ffi::LUA_MULTRET, stack_start + 1);
ffi::lua_remove(state, stack_start + 1);
if ret == ffi::LUA_OK {
Ok(())
} else {
Err(pop_error(state, ret))
}
}
// Call a function that calls into the Lua API and may trigger a Lua error (longjmp) in a safe way.
// Wraps the inner function in a call to `lua_pcall`, so the inner function only has access to a
// limited lua stack. `nargs` and `nresults` are similar to the parameters of `lua_pcall`, but the
// given function return type is not the return value count, instead the inner function return
// values are assumed to match the `nresults` param. Provided function must *not* panic, and since it
// will generally be lonjmping, should not contain any values that implements Drop.
// Internally uses 3 extra stack spaces, and does not call checkstack.
pub unsafe fn protect_lua_closure<F, R>(
state: *mut ffi::lua_State,
nargs: c_int,
nresults: c_int,
f: F,
) -> Result<R>
where
F: Fn(*mut ffi::lua_State) -> R,
R: Copy,
{
union URes<R: Copy> {
uninit: (),
init: R,
}
struct Params<F, R: Copy> {
function: F,
result: URes<R>,
nresults: c_int,
}
unsafe extern "C" fn do_call<F, R>(state: *mut ffi::lua_State) -> c_int
where
R: Copy,
F: Fn(*mut ffi::lua_State) -> R,
{
let params = ffi::lua_touserdata(state, -1) as *mut Params<F, R>;
ffi::lua_pop(state, 1);
(*params).result.init = ((*params).function)(state);
if (*params).nresults == ffi::LUA_MULTRET {
ffi::lua_gettop(state)
} else {
(*params).nresults
}
}
let stack_start = ffi::lua_gettop(state) - nargs;
ffi::lua_pushcfunction(state, error_traceback);
ffi::lua_pushcfunction(state, do_call::<F, R>);
if nargs > 0 {
ffi::lua_rotate(state, stack_start + 1, 2);
}
let mut params = Params {
function: f,
result: URes { uninit: () },
nresults,
};
ffi::lua_pushlightuserdata(state, &mut params as *mut Params<F, R> as *mut c_void);
let ret = ffi::lua_pcall(state, nargs + 1, nresults, stack_start + 1);
ffi::lua_remove(state, stack_start + 1);
if ret == ffi::LUA_OK {
// `LUA_OK` is only returned when the `do_call` function has completed successfully, so
// `params.result` is definitely initialized.
Ok(params.result.init)
} else {
Err(pop_error(state, ret))
}
}
// Pops an error off of the stack and returns it. The specific behavior depends on the type of the
// error at the top of the stack:
// 1) If the error is actually a WrappedPanic, this will continue the panic.
// 2) If the error on the top of the stack is actually a WrappedError, just returns it.
// 3) Otherwise, interprets the error as the appropriate lua error.
// Uses 2 stack spaces, does not call checkstack.
pub unsafe fn pop_error(state: *mut ffi::lua_State, err_code: c_int) -> Error {
mlua_debug_assert!(
err_code != ffi::LUA_OK && err_code != ffi::LUA_YIELD,
"pop_error called with non-error return code"
);
match get_gc_userdata::<WrappedFailure>(state, -1).as_mut() {
Some(WrappedFailure::Error(err)) => {
ffi::lua_pop(state, 1);
err.clone()
}
Some(WrappedFailure::Panic(panic)) => {
if let Some(p) = panic.take() {
resume_unwind(p);
} else {
Error::PreviouslyResumedPanic
}
}
_ => {
let err_string = to_string(state, -1);
ffi::lua_pop(state, 1);
match err_code {
ffi::LUA_ERRRUN => Error::RuntimeError(err_string),
ffi::LUA_ERRSYNTAX => {
Error::SyntaxError {
// This seems terrible, but as far as I can tell, this is exactly what the
// stock Lua REPL does.
incomplete_input: err_string.ends_with("<eof>")
|| err_string.ends_with("'<eof>'"),
message: err_string,
}
}
ffi::LUA_ERRERR => {
// This error is raised when the error handler raises an error too many times
// recursively, and continuing to trigger the error handler would cause a stack
// overflow. It is not very useful to differentiate between this and "ordinary"
// runtime errors, so we handle them the same way.
Error::RuntimeError(err_string)
}
ffi::LUA_ERRMEM => Error::MemoryError(err_string),
#[cfg(any(feature = "lua53", feature = "lua52"))]
ffi::LUA_ERRGCMM => Error::GarbageCollectorError(err_string),
_ => mlua_panic!("unrecognized lua error code"),
}
}
}
}
// Uses 3 stack spaces, does not call checkstack.
#[inline]
pub unsafe fn push_string<S: AsRef<[u8]> + ?Sized>(
state: *mut ffi::lua_State,
s: &S,
) -> Result<()> {
let s = s.as_ref();
protect_lua!(state, 0, 1, |state| {
ffi::lua_pushlstring(state, s.as_ptr() as *const c_char, s.len());
})
}
// Uses 3 stack spaces, does not call checkstack.
#[inline]
pub unsafe fn push_table(state: *mut ffi::lua_State, narr: c_int, nrec: c_int) -> Result<()> {
protect_lua!(state, 0, 1, |state| ffi::lua_createtable(state, narr, nrec))
}
// Uses 4 stack spaces, does not call checkstack.
pub unsafe fn rawset_field<S>(state: *mut ffi::lua_State, table: c_int, field: &S) -> Result<()>
where
S: AsRef<[u8]> + ?Sized,
{
let field = field.as_ref();
ffi::lua_pushvalue(state, table);
protect_lua!(state, 2, 0, |state| {
ffi::lua_pushlstring(state, field.as_ptr() as *const c_char, field.len());
ffi::lua_rotate(state, -3, 2);
ffi::lua_rawset(state, -3);
})
}
// Internally uses 3 stack spaces, does not call checkstack.
#[cfg(not(feature = "luau"))]
#[inline]
pub unsafe fn push_userdata<T>(state: *mut ffi::lua_State, t: T) -> Result<()> {
let ud = protect_lua!(state, 0, 1, |state| {
ffi::lua_newuserdata(state, mem::size_of::<T>()) as *mut T
})?;
ptr::write(ud, t);
Ok(())
}
// Internally uses 3 stack spaces, does not call checkstack.
#[cfg(feature = "luau")]
#[inline]
pub unsafe fn push_userdata<T>(state: *mut ffi::lua_State, t: T) -> Result<()> {
unsafe extern "C" fn destructor<T>(ud: *mut c_void) {
let ud = ud as *mut T;
if *(ud.offset(1) as *mut u8) == 0 {
ptr::drop_in_place(ud);
}
}
let ud = protect_lua!(state, 0, 1, |state| {
let size = mem::size_of::<T>() + 1;
ffi::lua_newuserdatadtor(state, size, destructor::<T>) as *mut T
})?;
ptr::write(ud, t);
*(ud.offset(1) as *mut u8) = 0; // Mark as not destructed
Ok(())
}
// Internally uses 3 stack spaces, does not call checkstack.
#[cfg(feature = "lua54")]
#[inline]
pub unsafe fn push_userdata_uv<T>(state: *mut ffi::lua_State, t: T, nuvalue: c_int) -> Result<()> {
let ud = protect_lua!(state, 0, 1, |state| {
ffi::lua_newuserdatauv(state, mem::size_of::<T>(), nuvalue) as *mut T
})?;
ptr::write(ud, t);
Ok(())
}
#[inline]
pub unsafe fn get_userdata<T>(state: *mut ffi::lua_State, index: c_int) -> *mut T {
let ud = ffi::lua_touserdata(state, index) as *mut T;
mlua_debug_assert!(!ud.is_null(), "userdata pointer is null");
ud
}
// Pops the userdata off of the top of the stack and returns it to rust, invalidating the lua
// userdata and gives it the special "destructed" userdata metatable. Userdata must not have been
// previously invalidated, and this method does not check for this.
// Uses 1 extra stack space and does not call checkstack.
pub unsafe fn take_userdata<T>(state: *mut ffi::lua_State) -> T {
// We set the metatable of userdata on __gc to a special table with no __gc method and with
// metamethods that trigger an error on access. We do this so that it will not be double
// dropped, and also so that it cannot be used or identified as any particular userdata type
// after the first call to __gc.
get_destructed_userdata_metatable(state);
ffi::lua_setmetatable(state, -2);
let ud = get_userdata::<T>(state, -1);
ffi::lua_pop(state, 1);
if cfg!(feature = "luau") {
*(ud.offset(1) as *mut u8) = 1; // Mark as destructed
}
ptr::read(ud)
}
// Pushes the userdata and attaches a metatable with __gc method.
// Internally uses 3 stack spaces, does not call checkstack.
pub unsafe fn push_gc_userdata<T: Any>(state: *mut ffi::lua_State, t: T) -> Result<()> {
push_userdata(state, t)?;
get_gc_metatable::<T>(state);
ffi::lua_setmetatable(state, -2);
Ok(())
}
// Uses 2 stack spaces, does not call checkstack
pub unsafe fn get_gc_userdata<T: Any>(state: *mut ffi::lua_State, index: c_int) -> *mut T {
let ud = ffi::lua_touserdata(state, index) as *mut T;
if ud.is_null() || ffi::lua_getmetatable(state, index) == 0 {
return ptr::null_mut();
}
get_gc_metatable::<T>(state);
let res = ffi::lua_rawequal(state, -1, -2);
ffi::lua_pop(state, 2);
if res == 0 {
return ptr::null_mut();
}
ud
}
unsafe extern "C" fn lua_error_impl(state: *mut ffi::lua_State) -> c_int {
ffi::lua_error(state);
}
unsafe extern "C" fn lua_isfunction_impl(state: *mut ffi::lua_State) -> c_int {
let t = ffi::lua_type(state, -1);
ffi::lua_pop(state, 1);
ffi::lua_pushboolean(state, (t == ffi::LUA_TFUNCTION) as c_int);
1
}
unsafe fn init_userdata_metatable_index(state: *mut ffi::lua_State) -> Result<()> {
let index_key = &USERDATA_METATABLE_INDEX as *const u8 as *const _;
if ffi::lua_rawgetp(state, ffi::LUA_REGISTRYINDEX, index_key) == ffi::LUA_TFUNCTION {
return Ok(());
}
ffi::lua_pop(state, 1);
// Create and cache `__index` helper
let code = cstr!(
r#"
local error, isfunction = ...
return function (__index, field_getters, methods)
return function (self, key)
if field_getters ~= nil then
local field_getter = field_getters[key]
if field_getter ~= nil then
return field_getter(self)
end
end
if methods ~= nil then
local method = methods[key]
if method ~= nil then
return method
end
end
if isfunction(__index) then
return __index(self, key)
elseif __index == nil then
error("attempt to get an unknown field '"..key.."'")
else
return __index[key]
end
end
end
"#
);
let code_len = CStr::from_ptr(code).to_bytes().len();
protect_lua!(state, 0, 1, |state| {
let ret = ffi::luaL_loadbuffer(state, code, code_len, cstr!("__mlua_index"));
if ret != ffi::LUA_OK {
ffi::lua_error(state);
}
ffi::lua_pushcfunction(state, lua_error_impl);
ffi::lua_pushcfunction(state, lua_isfunction_impl);
ffi::lua_call(state, 2, 1);
// Store in the registry
ffi::lua_pushvalue(state, -1);
ffi::lua_rawsetp(state, ffi::LUA_REGISTRYINDEX, index_key);
})
}
pub unsafe fn init_userdata_metatable_newindex(state: *mut ffi::lua_State) -> Result<()> {
let newindex_key = &USERDATA_METATABLE_NEWINDEX as *const u8 as *const _;
if ffi::lua_rawgetp(state, ffi::LUA_REGISTRYINDEX, newindex_key) == ffi::LUA_TFUNCTION {
return Ok(());
}
ffi::lua_pop(state, 1);
// Create and cache `__newindex` helper
let code = cstr!(
r#"
local error, isfunction = ...
return function (__newindex, field_setters)
return function (self, key, value)
if field_setters ~= nil then
local field_setter = field_setters[key]
if field_setter ~= nil then
field_setter(self, value)
return
end
end
if isfunction(__newindex) then
__newindex(self, key, value)
elseif __newindex == nil then
error("attempt to set an unknown field '"..key.."'")
else
__newindex[key] = value
end
end
end
"#
);
let code_len = CStr::from_ptr(code).to_bytes().len();
protect_lua!(state, 0, 1, |state| {
let ret = ffi::luaL_loadbuffer(state, code, code_len, cstr!("__mlua_newindex"));
if ret != ffi::LUA_OK {
ffi::lua_error(state);
}
ffi::lua_pushcfunction(state, lua_error_impl);
ffi::lua_pushcfunction(state, lua_isfunction_impl);
ffi::lua_call(state, 2, 1);
// Store in the registry
ffi::lua_pushvalue(state, -1);
ffi::lua_rawsetp(state, ffi::LUA_REGISTRYINDEX, newindex_key);
})
}
// Populates the given table with the appropriate members to be a userdata metatable for the given type.
// This function takes the given table at the `metatable` index, and adds an appropriate `__gc` member
// to it for the given type and a `__metatable` entry to protect the table from script access.
// The function also, if given a `field_getters` or `methods` tables, will create an `__index` metamethod
// (capturing previous one) to lookup in `field_getters` first, then `methods` and falling back to the
// captured `__index` if no matches found.
// The same is also applicable for `__newindex` metamethod and `field_setters` table.
// Internally uses 9 stack spaces and does not call checkstack.
pub unsafe fn init_userdata_metatable<T>(
state: *mut ffi::lua_State,
metatable: c_int,
field_getters: Option<c_int>,
field_setters: Option<c_int>,
methods: Option<c_int>,
) -> Result<()> {
ffi::lua_pushvalue(state, metatable);
if field_getters.is_some() || methods.is_some() {
// Push `__index` generator function
init_userdata_metatable_index(state)?;
push_string(state, "__index")?;
let index_type = ffi::lua_rawget(state, -3);
match index_type {
ffi::LUA_TNIL | ffi::LUA_TTABLE | ffi::LUA_TFUNCTION => {
for &idx in &[field_getters, methods] {
if let Some(idx) = idx {
ffi::lua_pushvalue(state, idx);
} else {
ffi::lua_pushnil(state);
}
}
// Generate `__index`
protect_lua!(state, 4, 1, fn(state) ffi::lua_call(state, 3, 1))?;
}
_ => mlua_panic!("improper __index type {}", index_type),
}
rawset_field(state, -2, "__index")?;
}
if let Some(field_setters) = field_setters {
// Push `__newindex` generator function
init_userdata_metatable_newindex(state)?;
push_string(state, "__newindex")?;
let newindex_type = ffi::lua_rawget(state, -3);
match newindex_type {
ffi::LUA_TNIL | ffi::LUA_TTABLE | ffi::LUA_TFUNCTION => {
ffi::lua_pushvalue(state, field_setters);
// Generate `__newindex`
protect_lua!(state, 3, 1, fn(state) ffi::lua_call(state, 2, 1))?;
}
_ => mlua_panic!("improper __newindex type {}", newindex_type),
}
rawset_field(state, -2, "__newindex")?;
}
#[cfg(not(feature = "luau"))]
{
ffi::lua_pushcfunction(state, userdata_destructor::<T>);
rawset_field(state, -2, "__gc")?;
}
ffi::lua_pushboolean(state, 0);
rawset_field(state, -2, "__metatable")?;
ffi::lua_pop(state, 1);
Ok(())
}
#[cfg(not(feature = "luau"))]
pub unsafe extern "C" fn userdata_destructor<T>(state: *mut ffi::lua_State) -> c_int {
// It's probably NOT a good idea to catch Rust panics in finalizer
// Lua 5.4 ignores it, other versions generates `LUA_ERRGCMM` without calling message handler
take_userdata::<T>(state);
0
}
// In the context of a lua callback, this will call the given function and if the given function
// returns an error, *or if the given function panics*, this will result in a call to `lua_error` (a
// longjmp). The error or panic is wrapped in such a way that when calling `pop_error` back on
// the Rust side, it will resume the panic.
//
// This function assumes the structure of the stack at the beginning of a callback, that the only
// elements on the stack are the arguments to the callback.
//
// This function uses some of the bottom of the stack for error handling, the given callback will be
// given the number of arguments available as an argument, and should return the number of returns
// as normal, but cannot assume that the arguments available start at 0.
pub unsafe fn callback_error<F, R>(state: *mut ffi::lua_State, f: F) -> R
where
F: FnOnce(c_int) -> Result<R>,
{
let nargs = ffi::lua_gettop(state);
// We need 2 extra stack spaces to store preallocated memory and error/panic metatable
let extra_stack = if nargs < 2 { 2 - nargs } else { 1 };
ffi::luaL_checkstack(
state,
extra_stack,
cstr!("not enough stack space for callback error handling"),
);
// We cannot shadow Rust errors with Lua ones, we pre-allocate enough memory
// to store a wrapped error or panic *before* we proceed.
let ud = WrappedFailure::new_userdata(state);
ffi::lua_rotate(state, 1, 1);
match catch_unwind(AssertUnwindSafe(|| f(nargs))) {
Ok(Ok(r)) => {
ffi::lua_remove(state, 1);
r
}
Ok(Err(err)) => {
ffi::lua_settop(state, 1);
let wrapped_error = ud as *mut WrappedFailure;
// Build `CallbackError` with traceback
let traceback = if ffi::lua_checkstack(state, ffi::LUA_TRACEBACK_STACK) != 0 {
ffi::luaL_traceback(state, state, ptr::null(), 0);
let traceback = to_string(state, -1);
ffi::lua_pop(state, 1);
traceback
} else {
"<not enough stack space for traceback>".to_string()
};
let cause = Arc::new(err);
ptr::write(
wrapped_error,
WrappedFailure::Error(Error::CallbackError { traceback, cause }),
);
get_gc_metatable::<WrappedFailure>(state);
ffi::lua_setmetatable(state, -2);
ffi::lua_error(state)
}
Err(p) => {
ffi::lua_settop(state, 1);
ptr::write(ud as *mut WrappedFailure, WrappedFailure::Panic(Some(p)));
get_gc_metatable::<WrappedFailure>(state);
ffi::lua_setmetatable(state, -2);
ffi::lua_error(state)
}
}
}
pub unsafe extern "C" fn error_traceback(state: *mut ffi::lua_State) -> c_int {
if ffi::lua_checkstack(state, 2) == 0 {
// If we don't have enough stack space to even check the error type, do
// nothing so we don't risk shadowing a rust panic.
return 1;
}
if get_gc_userdata::<WrappedFailure>(state, -1).is_null() {
let s = ffi::luaL_tolstring(state, -1, ptr::null_mut());
if ffi::lua_checkstack(state, ffi::LUA_TRACEBACK_STACK) != 0 {
ffi::luaL_traceback(state, state, s, 0);
ffi::lua_remove(state, -2);
}
}
1
}
// A variant of `pcall` that does not allow Lua to catch Rust panics from `callback_error`.
pub unsafe extern "C" fn safe_pcall(state: *mut ffi::lua_State) -> c_int {
ffi::luaL_checkstack(state, 2, ptr::null());
let top = ffi::lua_gettop(state);
if top == 0 {
ffi::lua_pushstring(state, cstr!("not enough arguments to pcall"));
ffi::lua_error(state);
}
if ffi::lua_pcall(state, top - 1, ffi::LUA_MULTRET, 0) == ffi::LUA_OK {
ffi::lua_pushboolean(state, 1);
ffi::lua_insert(state, 1);
ffi::lua_gettop(state)
} else {
if let Some(WrappedFailure::Panic(_)) =
get_gc_userdata::<WrappedFailure>(state, -1).as_ref()
{
ffi::lua_error(state);
}
ffi::lua_pushboolean(state, 0);
ffi::lua_insert(state, -2);
2
}
}
// A variant of `xpcall` that does not allow Lua to catch Rust panics from `callback_error`.
pub unsafe extern "C" fn safe_xpcall(state: *mut ffi::lua_State) -> c_int {
unsafe extern "C" fn xpcall_msgh(state: *mut ffi::lua_State) -> c_int {
ffi::luaL_checkstack(state, 2, ptr::null());
if let Some(WrappedFailure::Panic(_)) =
get_gc_userdata::<WrappedFailure>(state, -1).as_ref()
{
1
} else {
ffi::lua_pushvalue(state, ffi::lua_upvalueindex(1));
ffi::lua_insert(state, 1);
ffi::lua_call(state, ffi::lua_gettop(state) - 1, ffi::LUA_MULTRET);
ffi::lua_gettop(state)
}
}
ffi::luaL_checkstack(state, 2, ptr::null());
let top = ffi::lua_gettop(state);
if top < 2 {
ffi::lua_pushstring(state, cstr!("not enough arguments to xpcall"));
ffi::lua_error(state);
}
ffi::lua_pushvalue(state, 2);
ffi::lua_pushcclosure(state, xpcall_msgh, 1);
ffi::lua_copy(state, 1, 2);
ffi::lua_replace(state, 1);
if ffi::lua_pcall(state, ffi::lua_gettop(state) - 2, ffi::LUA_MULTRET, 1) == ffi::LUA_OK {
ffi::lua_pushboolean(state, 1);
ffi::lua_insert(state, 2);
ffi::lua_gettop(state) - 1
} else {
if let Some(WrappedFailure::Panic(_)) =
get_gc_userdata::<WrappedFailure>(state, -1).as_ref()
{
ffi::lua_error(state);
}
ffi::lua_pushboolean(state, 0);
ffi::lua_insert(state, -2);
2
}
}
// Returns Lua main thread for Lua >= 5.2 or checks that the passed thread is main for Lua 5.1.
// Does not call lua_checkstack, uses 1 stack space.
pub unsafe fn get_main_state(state: *mut ffi::lua_State) -> Option<*mut ffi::lua_State> {
#[cfg(any(feature = "lua54", feature = "lua53", feature = "lua52"))]
{
ffi::lua_rawgeti(state, ffi::LUA_REGISTRYINDEX, ffi::LUA_RIDX_MAINTHREAD);
let main_state = ffi::lua_tothread(state, -1);
ffi::lua_pop(state, 1);
Some(main_state)
}
#[cfg(any(feature = "lua51", feature = "luajit"))]
{
// Check the current state first
let is_main_state = ffi::lua_pushthread(state) == 1;
ffi::lua_pop(state, 1);
if is_main_state {
Some(state)
} else {
None
}
}
#[cfg(feature = "luau")]
Some(ffi::lua_mainthread(state))
}
// Initialize the internal (with __gc method) metatable for a type T.
// Uses 6 stack spaces and calls checkstack.
pub unsafe fn init_gc_metatable<T: Any>(
state: *mut ffi::lua_State,
customize_fn: Option<fn(*mut ffi::lua_State) -> Result<()>>,
) -> Result<()> {
check_stack(state, 6)?;
push_table(state, 0, 3)?;
#[cfg(not(feature = "luau"))]
{
ffi::lua_pushcfunction(state, userdata_destructor::<T>);
rawset_field(state, -2, "__gc")?;
}
ffi::lua_pushboolean(state, 0);
rawset_field(state, -2, "__metatable")?;
if let Some(f) = customize_fn {
f(state)?;
}
let type_id = TypeId::of::<T>();
let ref_addr = &METATABLE_CACHE[&type_id] as *const u8;
protect_lua!(state, 1, 0, |state| {
ffi::lua_rawsetp(state, ffi::LUA_REGISTRYINDEX, ref_addr as *const c_void);
})?;
Ok(())
}
pub unsafe fn get_gc_metatable<T: Any>(state: *mut ffi::lua_State) {
let type_id = TypeId::of::<T>();
let ref_addr =
mlua_expect!(METATABLE_CACHE.get(&type_id), "gc metatable does not exist") as *const u8;
ffi::lua_rawgetp(state, ffi::LUA_REGISTRYINDEX, ref_addr as *const c_void);
}
// Initialize the error, panic, and destructed userdata metatables.
pub unsafe fn init_error_registry(state: *mut ffi::lua_State) -> Result<()> {
check_stack(state, 7)?;
// Create error and panic metatables
unsafe extern "C" fn error_tostring(state: *mut ffi::lua_State) -> c_int {
callback_error(state, |_| {
check_stack(state, 3)?;
let err_buf = match get_gc_userdata::<WrappedFailure>(state, -1).as_ref() {
Some(WrappedFailure::Error(error)) => {
let err_buf_key = &ERROR_PRINT_BUFFER_KEY as *const u8 as *const c_void;
ffi::lua_rawgetp(state, ffi::LUA_REGISTRYINDEX, err_buf_key);
let err_buf = ffi::lua_touserdata(state, -1) as *mut String;
ffi::lua_pop(state, 2);
(*err_buf).clear();
// Depending on how the API is used and what error types scripts are given, it may
// be possible to make this consume arbitrary amounts of memory (for example, some
// kind of recursive error structure?)
let _ = write!(&mut (*err_buf), "{}", error);
Ok(err_buf)
}
Some(WrappedFailure::Panic(Some(ref panic))) => {
let err_buf_key = &ERROR_PRINT_BUFFER_KEY as *const u8 as *const c_void;
ffi::lua_rawgetp(state, ffi::LUA_REGISTRYINDEX, err_buf_key);
let err_buf = ffi::lua_touserdata(state, -1) as *mut String;
(*err_buf).clear();
ffi::lua_pop(state, 2);
if let Some(msg) = panic.downcast_ref::<&str>() {
let _ = write!(&mut (*err_buf), "{}", msg);
} else if let Some(msg) = panic.downcast_ref::<String>() {
let _ = write!(&mut (*err_buf), "{}", msg);
} else {
let _ = write!(&mut (*err_buf), "<panic>");
};
Ok(err_buf)
}
Some(WrappedFailure::Panic(None)) => Err(Error::PreviouslyResumedPanic),
_ => {
// I'm not sure whether this is possible to trigger without bugs in mlua?
Err(Error::UserDataTypeMismatch)
}
}?;
push_string(state, &*err_buf)?;
(*err_buf).clear();
Ok(1)
})
}
init_gc_metatable::<WrappedFailure>(
state,
Some(|state| {
ffi::lua_pushcfunction(state, error_tostring);
rawset_field(state, -2, "__tostring")
}),
)?;
// Create destructed userdata metatable
unsafe extern "C" fn destructed_error(state: *mut ffi::lua_State) -> c_int {
callback_error(state, |_| Err(Error::CallbackDestructed))
}
push_table(state, 0, 26)?;
ffi::lua_pushcfunction(state, destructed_error);
for &method in &[
"__add",
"__sub",
"__mul",
"__div",
"__mod",
"__pow",
"__unm",
#[cfg(any(feature = "lua54", feature = "lua53"))]
"__idiv",
#[cfg(any(feature = "lua54", feature = "lua53"))]
"__band",
#[cfg(any(feature = "lua54", feature = "lua53"))]
"__bor",
#[cfg(any(feature = "lua54", feature = "lua53"))]
"__bxor",
#[cfg(any(feature = "lua54", feature = "lua53"))]
"__bnot",
#[cfg(any(feature = "lua54", feature = "lua53"))]
"__shl",
#[cfg(any(feature = "lua54", feature = "lua53"))]
"__shr",
"__concat",
"__len",
"__eq",
"__lt",
"__le",
"__index",
"__newindex",
"__call",
"__tostring",
#[cfg(any(
feature = "lua54",
feature = "lua53",
feature = "lua52",
feature = "luajit52"
))]
"__pairs",
#[cfg(any(feature = "lua53", feature = "lua52", feature = "luajit52"))]
"__ipairs",
#[cfg(feature = "lua54")]
"__close",
] {
ffi::lua_pushvalue(state, -1);
rawset_field(state, -3, method)?;
}
ffi::lua_pop(state, 1);
protect_lua!(state, 1, 0, fn(state) {
let destructed_mt_key = &DESTRUCTED_USERDATA_METATABLE as *const u8 as *const c_void;
ffi::lua_rawsetp(state, ffi::LUA_REGISTRYINDEX, destructed_mt_key);
})?;
// Create error print buffer
init_gc_metatable::<String>(state, None)?;
push_gc_userdata(state, String::new())?;
protect_lua!(state, 1, 0, fn(state) {
let err_buf_key = &ERROR_PRINT_BUFFER_KEY as *const u8 as *const c_void;
ffi::lua_rawsetp(state, ffi::LUA_REGISTRYINDEX, err_buf_key);
})?;
Ok(())
}
pub(crate) enum WrappedFailure {
None,
Error(Error),
Panic(Option<Box<dyn Any + Send + 'static>>),
}
impl WrappedFailure {
pub(crate) unsafe fn new_userdata(state: *mut ffi::lua_State) -> *mut Self {
let size = mem::size_of::<WrappedFailure>();
#[cfg(feature = "luau")]
let ud = {
unsafe extern "C" fn destructor(p: *mut c_void) {
ptr::drop_in_place(p as *mut WrappedFailure);
}
ffi::lua_newuserdatadtor(state, size, destructor) as *mut Self
};
#[cfg(not(feature = "luau"))]
let ud = ffi::lua_newuserdata(state, size) as *mut Self;
ptr::write(ud, WrappedFailure::None);
ud
}
}
// Converts the given lua value to a string in a reasonable format without causing a Lua error or
// panicking.
pub(crate) unsafe fn to_string(state: *mut ffi::lua_State, index: c_int) -> String {
match ffi::lua_type(state, index) {
ffi::LUA_TNONE => "<none>".to_string(),
ffi::LUA_TNIL => "<nil>".to_string(),
ffi::LUA_TBOOLEAN => (ffi::lua_toboolean(state, index) != 1).to_string(),
ffi::LUA_TLIGHTUSERDATA => {
format!("<lightuserdata {:?}>", ffi::lua_topointer(state, index))
}
ffi::LUA_TNUMBER => {
let mut isint = 0;
let i = ffi::lua_tointegerx(state, -1, &mut isint);
if isint == 0 {
ffi::lua_tonumber(state, index).to_string()
} else {
i.to_string()
}
}
ffi::LUA_TSTRING => {
let mut size = 0;
// This will not trigger a 'm' error, because the reference is guaranteed to be of
// string type
let data = ffi::lua_tolstring(state, index, &mut size);
String::from_utf8_lossy(slice::from_raw_parts(data as *const u8, size)).into_owned()
}
ffi::LUA_TTABLE => format!("<table {:?}>", ffi::lua_topointer(state, index)),
ffi::LUA_TFUNCTION => format!("<function {:?}>", ffi::lua_topointer(state, index)),
ffi::LUA_TUSERDATA => format!("<userdata {:?}>", ffi::lua_topointer(state, index)),
ffi::LUA_TTHREAD => format!("<thread {:?}>", ffi::lua_topointer(state, index)),
_ => "<unknown>".to_string(),
}
}
pub(crate) unsafe fn get_destructed_userdata_metatable(state: *mut ffi::lua_State) {
let key = &DESTRUCTED_USERDATA_METATABLE as *const u8 as *const c_void;
ffi::lua_rawgetp(state, ffi::LUA_REGISTRYINDEX, key);
}
static DESTRUCTED_USERDATA_METATABLE: u8 = 0;
static ERROR_PRINT_BUFFER_KEY: u8 = 0;
static USERDATA_METATABLE_INDEX: u8 = 0;
static USERDATA_METATABLE_NEWINDEX: u8 = 0;
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