Wasmtime
func.hh
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1
5#ifndef WASMTIME_FUNC_HH
6#define WASMTIME_FUNC_HH
7
8#include <array>
9#include <wasmtime/error.hh>
10#include <wasmtime/extern_declare.hh>
11#include <wasmtime/func.h>
12#include <wasmtime/span.hh>
13#include <wasmtime/store.hh>
14#include <wasmtime/trap.hh>
16#include <wasmtime/types/val.hh>
17#include <wasmtime/val.hh>
18
19namespace wasmtime {
20
28class Caller {
29 friend class Func;
30 friend class Store;
32 Caller(wasmtime_caller_t *ptr) : ptr(ptr) {}
33
34public:
39 std::optional<Extern> get_export(std::string_view name);
40
42 Store::Context context() { return this; }
43};
44
45inline Store::Context::Context(Caller &caller)
46 : Context(wasmtime_caller_context(caller.ptr)) {}
47inline Store::Context::Context(Caller *caller) : Context(*caller) {}
48
49namespace detail {
50
53template <typename T> struct WasmType {
54 static const bool valid = false;
55};
56
59// NOLINTNEXTLINE
60#define NATIVE_WASM_TYPE(native, valkind, field) \
61 template <> struct WasmType<native> { \
62 static const bool valid = true; \
63 static const ValKind kind = ValKind::valkind; \
64 static void store(Store::Context cx, wasmtime_val_raw_t *p, \
65 const native &t) { \
66 (void)cx; \
67 p->field = t; \
68 } \
69 static native load(Store::Context cx, wasmtime_val_raw_t *p) { \
70 (void)cx; \
71 return p->field; \
72 } \
73 };
74
75NATIVE_WASM_TYPE(int32_t, I32, i32)
76NATIVE_WASM_TYPE(uint32_t, I32, i32)
77NATIVE_WASM_TYPE(int64_t, I64, i64)
78NATIVE_WASM_TYPE(uint64_t, I64, i64)
79NATIVE_WASM_TYPE(float, F32, f32)
80NATIVE_WASM_TYPE(double, F64, f64)
81
82#undef NATIVE_WASM_TYPE
83
86template <> struct WasmType<std::optional<ExternRef>> {
87 static const bool valid = true;
88 static const ValKind kind = ValKind::ExternRef;
89 static void store(Store::Context cx, wasmtime_val_raw_t *p,
90 const std::optional<ExternRef> &ref) {
91 if (ref) {
92 p->externref = wasmtime_externref_to_raw(cx.raw_context(), ref->raw());
93 } else {
94 p->externref = 0;
95 }
96 }
97 static std::optional<ExternRef> load(Store::Context cx,
99 if (p->externref == 0) {
100 return std::nullopt;
101 }
103 wasmtime_externref_from_raw(cx.raw_context(), p->externref, &val);
104 return ExternRef(val);
105 }
106};
107
109template <> struct WasmType<V128> {
110 static const bool valid = true;
111 static const ValKind kind = ValKind::V128;
112 static void store(Store::Context cx, wasmtime_val_raw_t *p, const V128 &t) {
113 (void)cx;
114 memcpy(&p->v128[0], &t.v128[0], sizeof(wasmtime_v128));
115 }
116 static V128 load(Store::Context cx, wasmtime_val_raw_t *p) {
117 (void)cx;
118 return p->v128;
119 }
120};
121
126template <typename T> struct WasmTypeList {
127 static const bool valid = WasmType<T>::valid;
128 static const size_t size = 1;
129 static bool matches(ValType::ListRef types) {
130 return WasmTypeList<std::tuple<T>>::matches(types);
131 }
132 static void store(Store::Context cx, wasmtime_val_raw_t *storage,
133 const T &t) {
134 WasmType<T>::store(cx, storage, t);
135 }
136 static T load(Store::Context cx, wasmtime_val_raw_t *storage) {
137 return WasmType<T>::load(cx, storage);
138 }
139 static std::vector<ValType> types() { return {WasmType<T>::kind}; }
140};
141
143template <> struct WasmTypeList<std::monostate> {
144 static const bool valid = true;
145 static const size_t size = 0;
146 static bool matches(ValType::ListRef types) { return types.size() == 0; }
147 static void store(Store::Context cx, wasmtime_val_raw_t *storage,
148 const std::monostate &t) {
149 (void)cx;
150 (void)storage;
151 (void)t;
152 }
153 static std::monostate load(Store::Context cx, wasmtime_val_raw_t *storage) {
154 (void)cx;
155 (void)storage;
156 return std::monostate();
157 }
158 static std::vector<ValType> types() { return {}; }
159};
160
162template <typename... T> struct WasmTypeList<std::tuple<T...>> {
163 static const bool valid = (WasmType<T>::valid && ...);
164 static const size_t size = sizeof...(T);
165 static bool matches(ValType::ListRef types) {
166 if (types.size() != size) {
167 return false;
168 }
169 size_t n = 0;
170 return ((WasmType<T>::kind == types.begin()[n++].kind()) && ...);
171 }
172 static void store(Store::Context cx, wasmtime_val_raw_t *storage,
173 const std::tuple<T...> &t) {
174 size_t n = 0;
175 std::apply(
176 [&](const auto &...val) {
177 (WasmType<T>::store(cx, &storage[n++], val), ...); // NOLINT
178 },
179 t);
180 }
181 static std::tuple<T...> load(Store::Context cx, wasmtime_val_raw_t *storage) {
182 (void)cx;
183 return std::tuple<T...>{WasmType<T>::load(cx, storage++)...}; // NOLINT
184 }
185 static std::vector<ValType> types() { return {WasmType<T>::kind...}; }
186};
187
191template <typename R> struct WasmHostRet {
192 using Results = WasmTypeList<R>;
193
194 template <typename F, typename... A>
195 static std::optional<Trap> invoke(F f, Caller cx, wasmtime_val_raw_t *raw,
196 A... args) {
197 auto ret = f(args...);
198 Results::store(cx, raw, ret);
199 return std::nullopt;
200 }
201};
202
204template <> struct WasmHostRet<void> {
205 using Results = WasmTypeList<std::tuple<>>;
206
207 template <typename F, typename... A>
208 static std::optional<Trap> invoke(F f, Caller cx, wasmtime_val_raw_t *raw,
209 A... args) {
210 (void)cx;
211 (void)raw;
212 f(args...);
213 return std::nullopt;
214 }
215};
216
217// Alternative method of returning "nothing" (also enables `std::monostate` in
218// the `R` type of `Result` below)
219template <> struct WasmHostRet<std::monostate> : public WasmHostRet<void> {};
220
223template <typename R> struct WasmHostRet<Result<R, Trap>> {
224 using Results = WasmTypeList<R>;
225
226 template <typename F, typename... A>
227 static std::optional<Trap> invoke(F f, Caller cx, wasmtime_val_raw_t *raw,
228 A... args) {
229 Result<R, Trap> ret = f(args...);
230 if (!ret) {
231 return ret.err();
232 }
233 Results::store(cx, raw, ret.ok());
234 return std::nullopt;
235 }
236};
237
238template <typename F, typename = void> struct WasmHostFunc;
239
242template <typename R, typename... A> struct WasmHostFunc<R (*)(A...)> {
243 using Params = WasmTypeList<std::tuple<A...>>;
244 using Results = typename WasmHostRet<R>::Results;
245
246 template <typename F>
247 static std::optional<Trap> invoke(F &f, Caller cx, wasmtime_val_raw_t *raw) {
248 auto params = Params::load(cx, raw);
249 return std::apply(
250 [&](const auto &...val) {
251 return WasmHostRet<R>::invoke(f, cx, raw, val...);
252 },
253 params);
254 }
255};
256
258template <typename R, typename... A>
259struct WasmHostFunc<R (*)(Caller, A...)> : public WasmHostFunc<R (*)(A...)> {
260 // Override `invoke` here to pass the `cx` as the first parameter
261 template <typename F>
262 static std::optional<Trap> invoke(F &f, Caller cx, wasmtime_val_raw_t *raw) {
263 auto params = WasmTypeList<std::tuple<A...>>::load(cx, raw);
264 return std::apply(
265 [&](const auto &...val) {
266 return WasmHostRet<R>::invoke(f, cx, raw, cx, val...);
267 },
268 params);
269 }
270};
271
273template <typename R, typename C, typename... A>
274struct WasmHostFunc<R (C::*)(A...)> : public WasmHostFunc<R (*)(A...)> {};
275
277template <typename R, typename C, typename... A>
278struct WasmHostFunc<R (C::*)(A...) const> : public WasmHostFunc<R (*)(A...)> {};
279
282template <typename R, typename C, typename... A>
283struct WasmHostFunc<R (C::*)(Caller, A...)>
284 : public WasmHostFunc<R (*)(Caller, A...)> {};
285
288template <typename R, typename C, typename... A>
289struct WasmHostFunc<R (C::*)(Caller, A...) const>
290 : public WasmHostFunc<R (*)(Caller, A...)> {};
291
294template <typename T>
295struct WasmHostFunc<T, std::void_t<decltype(&T::operator())>>
296 : public WasmHostFunc<decltype(&T::operator())> {};
297
298} // namespace detail
299
300using namespace detail;
301
302// forward-declaration for `Func::typed` below.
303template <typename Params, typename Results> class TypedFunc;
304
316class Func {
317 friend class Val;
318 friend class Instance;
319 friend class Linker;
320 template <typename Params, typename Results> friend class TypedFunc;
321
322 wasmtime_func_t func;
323
324 template <typename F>
325 static wasm_trap_t *raw_callback(void *env, wasmtime_caller_t *caller,
326 const wasmtime_val_t *args, size_t nargs,
327 wasmtime_val_t *results, size_t nresults) {
328 static_assert(alignof(Val) == alignof(wasmtime_val_t));
329 static_assert(sizeof(Val) == sizeof(wasmtime_val_t));
330 F *func = reinterpret_cast<F *>(env); // NOLINT
331 Span<const Val> args_span(reinterpret_cast<const Val *>(args), // NOLINT
332 nargs);
333 Span<Val> results_span(reinterpret_cast<Val *>(results), // NOLINT
334 nresults);
336 (*func)(Caller(caller), args_span, results_span);
337 if (!result) {
338 return result.err().ptr.release();
339 }
340 return nullptr;
341 }
342
343 template <typename F>
344 static wasm_trap_t *
345 raw_callback_unchecked(void *env, wasmtime_caller_t *caller,
346 wasmtime_val_raw_t *args_and_results,
347 size_t nargs_and_results) {
348 (void)nargs_and_results;
349 using HostFunc = WasmHostFunc<F>;
350 Caller cx(caller);
351 F *func = reinterpret_cast<F *>(env); // NOLINT
352 auto trap = HostFunc::invoke(*func, cx, args_and_results);
353 if (trap) {
354 return trap->ptr.release();
355 }
356 return nullptr;
357 }
358
359 template <typename F> static void raw_finalize(void *env) {
360 std::unique_ptr<F> ptr(reinterpret_cast<F *>(env)); // NOLINT
361 }
362
363public:
365 Func(wasmtime_func_t func) : func(func) {}
366
398 template <typename F,
399 std::enable_if_t<
400 std::is_invocable_r_v<Result<std::monostate, Trap>, F, Caller,
402 bool> = true>
403 Func(Store::Context cx, const FuncType &ty, F f) : func({}) {
404 wasmtime_func_new(cx.ptr, ty.ptr.get(), raw_callback<F>,
405 std::make_unique<F>(f).release(), raw_finalize<F>, &func);
406 }
407
446 template <typename F,
447 std::enable_if_t<WasmHostFunc<F>::Params::valid, bool> = true,
448 std::enable_if_t<WasmHostFunc<F>::Results::valid, bool> = true>
449 static Func wrap(Store::Context cx, F f) {
450 using HostFunc = WasmHostFunc<F>;
451 auto params = HostFunc::Params::types();
452 auto results = HostFunc::Results::types();
453 auto ty = FuncType::from_iters(params, results);
454 wasmtime_func_t func;
455 wasmtime_func_new_unchecked(cx.ptr, ty.ptr.get(), raw_callback_unchecked<F>,
456 std::make_unique<F>(f).release(),
457 raw_finalize<F>, &func);
458 return func;
459 }
460
481 template <typename I>
483 const I &end) const {
484 std::vector<wasmtime_val_t> raw_params;
485 raw_params.reserve(end - begin);
486 for (auto i = begin; i != end; i++) {
487 raw_params.push_back(i->val);
488 }
489 size_t nresults = this->type(cx)->results().size();
490 std::vector<wasmtime_val_t> raw_results(nresults);
491
492 wasm_trap_t *trap = nullptr;
493 auto *error =
494 wasmtime_func_call(cx.ptr, &func, raw_params.data(), raw_params.size(),
495 raw_results.data(), raw_results.capacity(), &trap);
496 if (error != nullptr) {
497 return TrapError(Error(error));
498 }
499 if (trap != nullptr) {
500 return TrapError(Trap(trap));
501 }
502
503 std::vector<Val> results;
504 results.reserve(nresults);
505 for (size_t i = 0; i < nresults; i++) {
506 results.push_back(raw_results[i]);
507 }
508 return results;
509 }
510
518 const std::vector<Val> &params) const {
519 return this->call(cx, params.begin(), params.end());
520 }
521
529 call(Store::Context cx, const std::initializer_list<Val> &params) const {
530 return this->call(cx, params.begin(), params.end());
531 }
532
535 return wasmtime_func_type(cx.ptr, &func);
536 }
537
555 template <typename Params, typename Results,
556 std::enable_if_t<WasmTypeList<Params>::valid, bool> = true,
557 std::enable_if_t<WasmTypeList<Results>::valid, bool> = true>
559 auto ty = this->type(cx);
560 if (!WasmTypeList<Params>::matches(ty->params()) ||
561 !WasmTypeList<Results>::matches(ty->results())) {
562 return Trap("static type for this function does not match actual type");
563 }
565 return ret;
566 }
567
569 const wasmtime_func_t &capi() const { return func; }
570};
571
576template <typename Params, typename Results> class TypedFunc {
577 friend class Func;
578 Func f;
579 TypedFunc(Func func) : f(func) {}
580
581public:
592 TrapResult<Results> call(Store::Context cx, Params params) const {
593 std::array<wasmtime_val_raw_t, std::max(WasmTypeList<Params>::size,
594 WasmTypeList<Results>::size)>
595 storage;
596 wasmtime_val_raw_t *ptr = storage.data();
597 if (ptr == nullptr)
598 ptr = reinterpret_cast<wasmtime_val_raw_t *>(alignof(wasmtime_val_raw_t));
599 WasmTypeList<Params>::store(cx, ptr, params);
600 wasm_trap_t *trap = nullptr;
601 auto *error = wasmtime_func_call_unchecked(cx.raw_context(), &f.func, ptr,
602 storage.size(), &trap);
603 if (error != nullptr) {
604 return TrapError(Error(error));
605 }
606 if (trap != nullptr) {
607 return TrapError(Trap(trap));
608 }
609 return WasmTypeList<Results>::load(cx, ptr);
610 }
611
613 const Func &func() const { return f; }
614};
615
616inline Val::Val(std::optional<Func> func) : val{} {
618 if (func) {
619 val.of.funcref = (*func).func;
620 } else {
621 wasmtime_funcref_set_null(&val.of.funcref);
622 }
623}
624
625inline Val::Val(Func func) : Val(std::optional(func)) {}
626inline Val::Val(ExternRef ptr) : Val(std::optional(ptr)) {}
627inline Val::Val(AnyRef ptr) : Val(std::optional(ptr)) {}
628
629inline std::optional<Func> Val::funcref() const {
630 if (val.kind != WASMTIME_FUNCREF) {
631 std::abort();
632 }
633 if (val.of.funcref.store_id == 0) {
634 return std::nullopt;
635 }
636 return Func(val.of.funcref);
637}
638
640template <> struct detail::WasmType<std::optional<Func>> {
642 static const bool valid = true;
644 static const ValKind kind = ValKind::FuncRef;
646 static void store(Store::Context cx, wasmtime_val_raw_t *p,
647 const std::optional<Func> func) {
648 if (func) {
649 p->funcref = wasmtime_func_to_raw(cx.raw_context(), &func->capi());
650 } else {
651 p->funcref = 0;
652 }
653 }
655 static std::optional<Func> load(Store::Context cx, wasmtime_val_raw_t *p) {
656 if (p->funcref == 0) {
657 return std::nullopt;
658 }
659 wasmtime_func_t ret;
660 wasmtime_func_from_raw(cx.raw_context(), p->funcref, &ret);
661 return ret;
662 }
663};
664
665} // namespace wasmtime
666
667#endif // WASMTIME_FUNC_HH
Representation of a WebAssembly anyref value.
Definition: val.hh:80
Structure provided to host functions to lookup caller information or acquire a Store::Context.
Definition: func.hh:28
std::optional< Extern > get_export(std::string_view name)
Definition: extern.hh:53
Store::Context context()
Explicitly acquire a Store::Context from this Caller.
Definition: func.hh:42
Errors coming from Wasmtime.
Definition: error.hh:25
Representation of a WebAssembly externref value.
Definition: val.hh:28
Type information for a WebAssembly function.
Definition: types/func.hh:15
static FuncType from_iters(P params, R results)
Creates a new function type from the given list of parameters and results.
Definition: types/func.hh:75
Representation of a WebAssembly function.
Definition: func.hh:316
TrapResult< std::vector< Val > > call(Store::Context cx, const I &begin, const I &end) const
Invoke a WebAssembly function.
Definition: func.hh:482
Func(wasmtime_func_t func)
Creates a new function from the raw underlying C API representation.
Definition: func.hh:365
FuncType type(Store::Context cx) const
Returns the type of this function.
Definition: func.hh:534
TrapResult< std::vector< Val > > call(Store::Context cx, const std::vector< Val > &params) const
Helper function for call(Store::Context cx, const I &begin, const I &end)
Definition: func.hh:517
static Func wrap(Store::Context cx, F f)
Creates a new host function from the provided callback f, inferring the WebAssembly function type fro...
Definition: func.hh:449
TrapResult< std::vector< Val > > call(Store::Context cx, const std::initializer_list< Val > &params) const
Helper function for call(Store::Context cx, const I &begin, const I &end)
Definition: func.hh:529
const wasmtime_func_t & capi() const
Returns the raw underlying C API function this is using.
Definition: func.hh:569
Func(Store::Context cx, const FuncType &ty, F f)
Creates a new host-defined function.
Definition: func.hh:403
Result< TypedFunc< Params, Results >, Trap > typed(Store::Context cx) const
Statically checks this function against the provided types.
Definition: func.hh:558
A WebAssembly instance.
Definition: instance.hh:31
Helper class for linking modules together with name-based resolution.
Definition: linker.hh:25
Fallible result type used for Wasmtime.
Definition: error.hh:82
E && err()
Returns the error, if present, aborts if this is not an error.
Definition: error.hh:96
Span class used when c++20 is not available.
Definition: span.hh:47
An interior pointer into a Store.
Definition: store.hh:60
wasmtime_context_t * raw_context()
Returns the raw context pointer for the C API.
Definition: store.hh:153
Owner of all WebAssembly objects.
Definition: store.hh:33
Information about a WebAssembly trap.
Definition: trap.hh:113
A version of a WebAssembly Func where the type signature of the function is statically known.
Definition: func.hh:576
const Func & func() const
Returns the underlying un-typed Func for this function.
Definition: func.hh:613
TrapResult< Results > call(Store::Context cx, Params params) const
Calls this function with the provided parameters.
Definition: func.hh:592
Representation of a generic WebAssembly value.
Definition: val.hh:156
std::optional< Func > funcref() const
Definition: func.hh:629
void wasmtime_func_from_raw(wasmtime_context_t *context, void *raw, wasmtime_func_t *ret)
Converts a raw nonzero funcref value from wasmtime_val_raw_t into a wasmtime_func_t.
wasmtime_error_t * wasmtime_func_call(wasmtime_context_t *store, const wasmtime_func_t *func, const wasmtime_val_t *args, size_t nargs, wasmtime_val_t *results, size_t nresults, wasm_trap_t **trap)
Call a WebAssembly function.
void * wasmtime_func_to_raw(wasmtime_context_t *context, const wasmtime_func_t *func)
Converts a func which belongs to context into a usize parameter that is suitable for insertion into a...
wasmtime_error_t * wasmtime_func_call_unchecked(wasmtime_context_t *store, const wasmtime_func_t *func, wasmtime_val_raw_t *args_and_results, size_t args_and_results_len, wasm_trap_t **trap)
Call a WebAssembly function in an "unchecked" fashion.
void wasmtime_func_new(wasmtime_context_t *store, const wasm_functype_t *type, wasmtime_func_callback_t callback, void *env, void(*finalizer)(void *), wasmtime_func_t *ret)
Creates a new host-defined function.
wasmtime_context_t * wasmtime_caller_context(wasmtime_caller_t *caller)
Returns the store context of the caller object.
void wasmtime_func_new_unchecked(wasmtime_context_t *store, const wasm_functype_t *type, wasmtime_func_unchecked_callback_t callback, void *env, void(*finalizer)(void *), wasmtime_func_t *ret)
Creates a new host function in the same manner of wasmtime_func_new, but the function-to-call has no ...
wasm_functype_t * wasmtime_func_type(const wasmtime_context_t *store, const wasmtime_func_t *func)
Returns the type of the function specified.
#define NATIVE_WASM_TYPE(native, valkind, field)
Definition: func.hh:60
Opaque struct representing a wasm trap.
Structure used to represent either a Trap or an Error.
Definition: trap.hh:165
A host-defined un-forgeable reference to pass into WebAssembly.
Definition: val.h:180
Representation of a function in Wasmtime.
Definition: extern.h:25
uint64_t store_id
Definition: extern.h:31
Container for different kinds of wasm values.
Definition: val.h:460
wasmtime_valkind_t kind
Discriminant of which field of of is valid.
Definition: val.h:462
wasmtime_valunion_t of
Container for the extern item's value.
Definition: val.h:464
ValKind
Different kinds of types accepted by Wasmtime.
Definition: types/val.hh:16
@ V128
WebAssembly's v128 type from the simd proposal.
Container for possible wasm values.
Definition: val.h:384
uint32_t externref
Definition: val.h:420
wasmtime_v128 v128
Definition: val.h:404
void * funcref
Definition: val.h:427
wasmtime_func_t funcref
Definition: val.h:348
uint32_t wasmtime_externref_to_raw(wasmtime_context_t *context, const wasmtime_externref_t *ref)
Converts a wasmtime_externref_t to a raw value suitable for storing into a wasmtime_val_raw_t.
union wasmtime_val_raw wasmtime_val_raw_t
Convenience alias for wasmtime_val_raw.
uint8_t wasmtime_v128[16]
A 128-bit value representing the WebAssembly v128 type. Bytes are stored in little-endian order.
Definition: val.h:319
void wasmtime_externref_from_raw(wasmtime_context_t *context, uint32_t raw, wasmtime_externref_t *out)
Converts a raw externref value coming from wasmtime_val_raw_t into a wasmtime_externref_t.
#define WASMTIME_FUNCREF
Value of wasmtime_valkind_t meaning that wasmtime_val_t is a funcref.
Definition: val.h:309