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1// Copyright (c) 2026 Cloudflare, Inc.
2// Licensed under the Apache 2.0 license found in the LICENSE file or at:
3// https://opensource.org/licenses/Apache-2.0
4 
5#pragma once
6 
7// This header contains template implementations that require complete type definitions.
8// It should be included after workerd/rust/jsg/v8.rs.h which defines the complete types.
9 
10#include <workerd/rust/jsg/ffi.h>
11#include <workerd/rust/jsg/v8.rs.h>
12 
13namespace workerd::rust::jsg {
14 
15// Local<T>
16static_assert(sizeof(v8::Local<v8::Value>) == 8, "Size should match");
17static_assert(alignof(v8::Local<v8::Value>) == 8, "Alignment should match");
18 
19template <typename T>
20inline Local to_ffi(v8::Local<T>&& value) {
21 size_t result;
22 auto ptr_void = reinterpret_cast<void*>(&result);
23 new (ptr_void) v8::Local<T>(kj::mv(value));
24 return Local{result};
25}
26 
27template <typename T>
28inline v8::Local<T> local_from_ffi(Local&& value) {
29 auto ptr_void = reinterpret_cast<void*>(&value.ptr);
30 return *reinterpret_cast<v8::Local<T>*>(ptr_void);
31}
32 
33template <typename T>
34inline const v8::Local<T>& local_as_ref_from_ffi(const Local& value) {
35 auto ptr_void = reinterpret_cast<const void*>(&value.ptr);
36 return *reinterpret_cast<const v8::Local<T>*>(ptr_void);
37}
38 
39// MaybeLocal<T>
40// v8::MaybeLocal<T> is exactly one Local<T> field at offset 0, so it has the same
41// size and layout as ffi::Local (one pointer-sized word, zero means empty).
42static_assert(sizeof(v8::MaybeLocal<v8::Value>) == sizeof(MaybeLocal), "Size should match");
43static_assert(alignof(v8::MaybeLocal<v8::Value>) == alignof(MaybeLocal), "Alignment should match");
44 
45template <typename T>
46inline MaybeLocal maybe_local_to_ffi(v8::MaybeLocal<T> value) {
47 size_t result;
48 auto ptr_void = reinterpret_cast<void*>(&result);
49 new (ptr_void) v8::MaybeLocal<T>(value);
50 return MaybeLocal{result};
51}
52 
53// Global<T>
54//
55// ffi::Global stores only the strong v8::Global<v8::Value> in `ptr`.
56// The traced v8::TracedReference<v8::Data> slot lives in Global<T>::traced_ptr
57// on the Rust side (as UnsafeCell<usize>), passed by raw pointer to
58// wrappable_visit_global and wrappable_global_reset.
59static_assert(sizeof(v8::Global<v8::Value>) == sizeof(size_t), "Global must be pointer-sized");
60static_assert(sizeof(v8::TracedReference<v8::Data>) == sizeof(size_t),
61 "TracedReference must be pointer-sized");
62static_assert(sizeof(Global) == sizeof(size_t), "ffi::Global must hold exactly one pointer slot");
63static_assert(alignof(v8::Global<v8::Value>) == alignof(Global), "Alignment should match");
64 
65template <typename T>
66inline Global to_ffi(v8::Global<T>&& value) {
67 size_t strong_slot;
68 auto ptr_void = reinterpret_cast<void*>(&strong_slot);
69 new (ptr_void) v8::Global<T>(kj::mv(value));
70 return Global{strong_slot};
71}
72 
73template <typename T>
74inline v8::Global<T> global_from_ffi(Global&& value) {
75 auto ptr_void = reinterpret_cast<void*>(&value.ptr);
76 return kj::mv(*reinterpret_cast<v8::Global<T>*>(ptr_void));
77}
78 
79template <typename T>
80inline const v8::Global<T>& global_as_ref_from_ffi(const Global& value) {
81 auto ptr_void = reinterpret_cast<const void*>(&value.ptr);
82 return *reinterpret_cast<const v8::Global<T>*>(ptr_void);
83}
84 
85template <typename T>
86inline v8::Global<T>* global_as_ref_from_ffi(Global& value) {
87 auto ptr_void = reinterpret_cast<void*>(&value.ptr);
88 return reinterpret_cast<v8::Global<T>*>(ptr_void);
89}
90 
91// TracedReference
92static_assert(sizeof(v8::TracedReference<v8::Data>) == sizeof(TracedReference),
93 "TracedReference size must match");
94static_assert(alignof(v8::TracedReference<v8::Data>) == alignof(TracedReference),
95 "TracedReference alignment must match");
96 
97inline v8::TracedReference<v8::Data>& traced_ref_from_ffi(TracedReference& value) {
98 return *reinterpret_cast<v8::TracedReference<v8::Data>*>(&value);
99}
100 
101// GcVisitor - wraps a pointer to jsg::GcVisitor
102static_assert(sizeof(::workerd::jsg::GcVisitor*) == sizeof(GcVisitor), "Size should match");
103static_assert(alignof(::workerd::jsg::GcVisitor*) == alignof(GcVisitor), "Alignment should match");
104 
105inline GcVisitor to_ffi(::workerd::jsg::GcVisitor* visitor) {
106 return GcVisitor{reinterpret_cast<size_t>(visitor)};
107}
108 
109inline ::workerd::jsg::GcVisitor* gc_visitor_from_ffi(GcVisitor* value) {
110 return reinterpret_cast<::workerd::jsg::GcVisitor*>(value->ptr);
111}
112 
113} // namespace workerd::rust::jsg