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[emval] Transfer ownership of handles to JS when moveable. #21436

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[emval] Transfer ownership of handles to JS when moveable. #21436

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15 changes: 11 additions & 4 deletions src/embind/emval.js
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Original file line number Diff line number Diff line change
Expand Up @@ -65,17 +65,24 @@ var LibraryEmVal = {
return symbol;
},

$Emval__deps: ['$emval_freelist', '$emval_handles', '$throwBindingError', '$init_emval'],
$Emval__deps: ['$emval_freelist', '$emval_handles', '$throwBindingError', '$init_emval', '_emval_decref'],
$Emval: {
toValue: (handle) => {
if (!handle) {
throwBindingError('Cannot use deleted val. handle = ' + handle);
}
let decref;
if (handle % 2 == 1) {
handle = handle - 1;
decref = __emval_decref;
}
#if ASSERTIONS
// handle 2 is supposed to be `undefined`.
assert(handle === 2 || emval_handles[handle] !== undefined && handle % 2 === 0, `invalid handle: ${handle}`);
assert(handle === 2 || emval_handles[handle] !== undefined, `invalid handle: ${handle}`);
#endif
return emval_handles[handle];
const value = emval_handles[handle];
decref && decref(handle);
return value;
},

toHandle: (value) => {
Expand Down Expand Up @@ -203,7 +210,7 @@ var LibraryEmVal = {
return Emval.toHandle(Module[name]);
},

_emval_get_property__deps: ['$Emval'],
_emval_get_property__deps: ['$Emval', '_emval_decref'],
_emval_get_property: (handle, key) => {
handle = Emval.toValue(handle);
key = Emval.toValue(key);
Expand Down
128 changes: 110 additions & 18 deletions system/include/emscripten/val.h
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Original file line number Diff line number Diff line change
Expand Up @@ -307,7 +307,7 @@ class val {
internal::typeSupportsMemoryView<
typename std::iterator_traits<Iter>::value_type>()) {
val view{ typed_memory_view(std::distance(begin, end), std::to_address(begin)) };
return val(internal::_emval_new_array_from_memory_view(view.as_handle()));
return val(internal::_emval_new_array_from_memory_view(js_ref(view)));
}
// For numeric arrays, following codes are unreachable and the compiler
// will do 'dead code elimination'.
Expand All @@ -325,7 +325,7 @@ class val {
if constexpr (internal::typeSupportsMemoryView<T>()) {
// for numeric types, pass memory view and copy in JS side one-off
val view{ typed_memory_view(vec.size(), vec.data()) };
return val(internal::_emval_new_array_from_memory_view(view.as_handle()));
return val(internal::_emval_new_array_from_memory_view(js_ref(view)));
} else {
return array(vec.begin(), vec.end());
}
Expand Down Expand Up @@ -455,11 +455,23 @@ class val {
return instanceof(global("Array"));
}

bool equals(const val& v) const {
return internal::_emval_equals(as_handle(), v.as_handle());
template <typename T>
bool equals(const T& v) const& {
return internal::_emval_equals(as_handle(), js_ref(v));
}

bool operator==(const val& v) const {
template <typename T>
bool equals(const T& v) && {
return internal::_emval_equals(release_ownership_to_js(), js_ref(v));
}

template <typename T>
bool operator==(const T& v) const& {
return equals(v);
}

template <typename T>
bool operator==(const T& v) && {
return equals(v);
}

Expand Down Expand Up @@ -492,18 +504,23 @@ class val {
}

template<typename T>
val operator[](const T& key) const {
return val(internal::_emval_get_property(as_handle(), val_ref(key).as_handle()));
val operator[](const T& key) const& {
return val(internal::_emval_get_property(as_handle(), js_ref(key)));
}

template<typename T>
val operator[](const T& key) && {
return val(internal::_emval_get_property(release_ownership_to_js(), js_ref(key)));
}

template<typename K, typename V>
void set(const K& key, const V& value) {
internal::_emval_set_property(as_handle(), val_ref(key).as_handle(), val_ref(value).as_handle());
internal::_emval_set_property(as_handle(), js_ref(key), js_ref(value));
}

template<typename T>
bool delete_(const T& property) const {
return internal::_emval_delete(as_handle(), val_ref(property).as_handle());
return internal::_emval_delete(as_handle(), js_ref(property));
}

template<typename... Args>
Expand Down Expand Up @@ -535,7 +552,7 @@ class val {
}

template<typename T, typename ...Policies>
T as(Policies...) const {
T as(Policies...) const& {
using namespace internal;

typedef BindingType<T> BT;
Expand All @@ -550,45 +567,105 @@ class val {
return fromGenericWireType<T>(result);
}

template<typename T, typename ...Policies>
T as(Policies...) && {
using namespace internal;

typedef BindingType<T> BT;
typename WithPolicies<Policies...>::template ArgTypeList<T> targetType;

EM_DESTRUCTORS destructors = nullptr;
EM_GENERIC_WIRE_TYPE result = _emval_as(
release_ownership_to_js(),
targetType.getTypes()[0],
&destructors);
DestructorsRunner dr(destructors);
return fromGenericWireType<T>(result);
}

#ifdef __wasm64__
template<>
long as<long>() const {
long as<long>() const& {
using namespace internal;

typedef BindingType<long> BT;
typename WithPolicies<>::template ArgTypeList<long> targetType;

return _emval_as_int64(as_handle(), targetType.getTypes()[0]);
}

template<>
long as<long>() &&{
using namespace internal;

typedef BindingType<long> BT;
typename WithPolicies<>::template ArgTypeList<long> targetType;

// TODO
return _emval_as_int64(as_handle(), targetType.getTypes()[0]);
}

template<>
unsigned long as<unsigned long>() const {
unsigned long as<unsigned long>() const& {
using namespace internal;

typedef BindingType<unsigned long> BT;
typename WithPolicies<>::template ArgTypeList<unsigned long> targetType;

return _emval_as_uint64(as_handle(), targetType.getTypes()[0]);
}

template<>
unsigned long as<unsigned long>() && {
using namespace internal;

typedef BindingType<unsigned long> BT;
typename WithPolicies<>::template ArgTypeList<unsigned long> targetType;

// TODO
return _emval_as_uint64(as_handle(), targetType.getTypes()[0]);
}
#endif

template<>
int64_t as<int64_t>() const {
int64_t as<int64_t>() const& {
using namespace internal;

typedef BindingType<int64_t> BT;
typename WithPolicies<>::template ArgTypeList<int64_t> targetType;

return _emval_as_int64(as_handle(), targetType.getTypes()[0]);
}

template<>
int64_t as<int64_t>() && {
using namespace internal;

typedef BindingType<int64_t> BT;
typename WithPolicies<>::template ArgTypeList<int64_t> targetType;

// TODO
return _emval_as_int64(as_handle(), targetType.getTypes()[0]);
}

template<>
uint64_t as<uint64_t>() const {
uint64_t as<uint64_t>() const& {
using namespace internal;

typedef BindingType<uint64_t> BT;
typename WithPolicies<>::template ArgTypeList<uint64_t> targetType;

return _emval_as_uint64(as_handle(), targetType.getTypes()[0]);
}

template<>
uint64_t as<uint64_t>() && {
using namespace internal;

typedef BindingType<uint64_t> BT;
typename WithPolicies<>::template ArgTypeList<uint64_t> targetType;

// TODO
return _emval_as_uint64(as_handle(), targetType.getTypes()[0]);
}

Expand Down Expand Up @@ -664,13 +741,28 @@ class val {
return fromGenericWireType<Ret>(result);
}

// Invalidates this instance and returns handle for JS ownership.
// Expected to be immediately use by Emval.toValue() which will decref
// the handle.
// Takes advantage of the even-only property of handle to encode this
// ownership transfer as an odd handle.
EM_VAL release_ownership_to_js() {
EM_VAL taken = as_handle();
handle = 0;
return reinterpret_cast<EM_VAL>(reinterpret_cast<uint32_t>(taken) + 1);
}

template<typename T>
val val_ref(const T& v) const {
return val(v);
static EM_VAL js_ref(const T& v) {
return val(v).release_ownership_to_js();
}

static EM_VAL js_ref(val&& v) {
return v.release_ownership_to_js();
}

const val& val_ref(const val& v) const {
return v;
static EM_VAL js_ref(const val& v) {
return v.as_handle();
}

pthread_t thread;
Expand Down
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