wasmtime

package module
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README

wasmtime-go

Go embedding of Wasmtime

A Bytecode Alliance project

CI status Documentation Code Coverage

Installation

go get -u github.com/bytecodealliance/wasmtime-go/v19@v19.0.0

Be sure to check out the API documentation!

This Go library uses CGO to consume the C API of the Wasmtime project which is written in Rust. Precompiled binaries of Wasmtime are checked into this repository on tagged releases so you won't have to install Wasmtime locally, but it means that this project only works on Linux x86_64, macOS x86_64 , and Windows x86_64 currently. Building on other platforms will need to arrange to build Wasmtime and use CGO_* env vars to compile correctly.

This project has been tested with Go 1.13 or later.

If you are a bazel user, add following to your WORKSPACE file:

go_repository(
    name = "com_github_bytecodealliance_wasmtime_go",
    importpath = "github.com/bytecodealliance/wasmtime-go/v19",
    version = "v19.0.0",
)

Usage

A "Hello, world!" example of using this package looks like:

package main

import (
    "fmt"
    "github.com/bytecodealliance/wasmtime-go/v19"
)

func main() {
    // Almost all operations in wasmtime require a contextual `store`
    // argument to share, so create that first
    store := wasmtime.NewStore(wasmtime.NewEngine())

    // Compiling modules requires WebAssembly binary input, but the wasmtime
    // package also supports converting the WebAssembly text format to the
    // binary format.
    wasm, err := wasmtime.Wat2Wasm(`
      (module
        (import "" "hello" (func $hello))
        (func (export "run")
          (call $hello))
      )
    `)
    check(err)

    // Once we have our binary `wasm` we can compile that into a `*Module`
    // which represents compiled JIT code.
    module, err := wasmtime.NewModule(store.Engine, wasm)
    check(err)

    // Our `hello.wat` file imports one item, so we create that function
    // here.
    item := wasmtime.WrapFunc(store, func() {
        fmt.Println("Hello from Go!")
    })

    // Next up we instantiate a module which is where we link in all our
    // imports. We've got one import so we pass that in here.
    instance, err := wasmtime.NewInstance(store, module, []wasmtime.AsExtern{item})
    check(err)

    // After we've instantiated we can lookup our `run` function and call
    // it.
    run := instance.GetFunc(store, "run")
    if run == nil {
        panic("not a function")
    }
    _, err = run.Call(store)
    check(err)
}

func check(e error) {
    if e != nil {
        panic(e)
    }
}

Contributing

So far this extension has been written by folks who are primarily Rust programmers, so it's highly likely that there's some faux pas in terms of Go idioms. Feel free to send a PR to help make things more idiomatic if you see something!

To work on this extension locally you'll first want to clone the project:

$ git clone https://github.com/bytecodealliance/wasmtime-go

Next up you'll want to have a local Wasmtime build available.

You'll need to build at least the wasmtime-c-api crate, which, at the time of this writing, would be:

$ cargo build -p wasmtime-c-api

Once you've got that you can set up the environment of this library with:

$ ./ci/local.sh /path/to/wasmtime

This will create a build directory which has the compiled libraries and header files. Next up you can run normal commands such as:

$ go test

And after that you should be good to go!

Release Checklist

First run:

$ python3 ci/download-wasmtime.py
$ go test

Make sure everything passes at the current version.

Next run:

$ git ls-files | xargs sed -i 's/v16/v17/g'
$ python3 ci/download-wasmtime.py
$ go test

Fix all errors and such and then commit and make a PR.

Once merged checkout main and do:

$ rm .gitignore
$ python3 ci/download-wasmtime.py
$ git add .
$ git commit -m 'v19.0.0 release artifacts'
$ git tag v19.0.0

and push up the tag

Documentation

Overview

Package wasmtime is a WebAssembly runtime for Go powered by Wasmtime.

This package provides everything necessary to compile and execute WebAssembly modules as part of a Go program. Wasmtime is a JIT compiler written in Rust, and can be found at https://github.com/bytecodealliance/wasmtime. This package is a binding to the C API provided by Wasmtime.

The API of this Go package is intended to mirror the Rust API (https://docs.rs/wasmtime) relatively closely, so if you find something is under-documented here then you may have luck consulting the Rust documentation as well. As always though feel free to file any issues at https://github.com/bytecodealliance/wasmtime-go/issues/new.

It's also worth pointing out that the authors of this package up to this point primarily work in Rust, so if you've got suggestions of how to make this package more idiomatic for Go we'd love to hear your thoughts!

Example (Gcd)

An example of a wasm module which calculates the GCD of two numbers 

store := wasmtime.NewStore(wasmtime.NewEngine())
wasm, err := wasmtime.Wat2Wasm(`
	(module
	  (func $gcd (param i32 i32) (result i32)
	    (local i32)
	    block  ;; label = @1
	      block  ;; label = @2
	        local.get 0
	        br_if 0 (;@2;)
	        local.get 1
	        local.set 2
	        br 1 (;@1;)
	      end
	      loop  ;; label = @2
	        local.get 1
	        local.get 0
	        local.tee 2
	        i32.rem_u
	        local.set 0
	        local.get 2
	        local.set 1
	        local.get 0
	        br_if 0 (;@2;)
	      end
	    end
	    local.get 2
	  )
	  (export "gcd" (func $gcd))
	)
	`)
if err != nil {
	log.Fatal(err)
}
module, err := wasmtime.NewModule(store.Engine, wasm)
if err != nil {
	log.Fatal(err)
}
instance, err := wasmtime.NewInstance(store, module, []wasmtime.AsExtern{})
if err != nil {
	log.Fatal(err)
}
run := instance.GetFunc(store, "gcd")
result, err := run.Call(store, 6, 27)
if err != nil {
	log.Fatal(err)
}
fmt.Printf("gcd(6, 27) = %d\n", result.(int32))

Output:

gcd(6, 27) = 3
Example (Hello)

An example of instantiating a small wasm module which imports functionality from the host, then calling into wasm which calls back into the host. 

// Almost all operations in wasmtime require a contextual `store`
// argument to share, so create that first
store := wasmtime.NewStore(wasmtime.NewEngine())

// Compiling modules requires WebAssembly binary input, but the wasmtime
// package also supports converting the WebAssembly text format to the
// binary format.
wasm, err := wasmtime.Wat2Wasm(`
	(module
	  (import "" "hello" (func $hello))
	  (func (export "run")
	    (call $hello)
	  )
	)
	`)
if err != nil {
	log.Fatal(err)
}

// Once we have our binary `wasm` we can compile that into a `*Module`
// which represents compiled JIT code.
module, err := wasmtime.NewModule(store.Engine, wasm)
if err != nil {
	log.Fatal(err)
}

// Our `hello.wat` file imports one item, so we create that function
// here.
item := wasmtime.WrapFunc(store, func() {
	fmt.Println("Hello from Go!")
})

// Next up we instantiate a module which is where we link in all our
// imports. We've got one import so we pass that in here.
instance, err := wasmtime.NewInstance(store, module, []wasmtime.AsExtern{item})
if err != nil {
	log.Fatal(err)
}

// After we've instantiated we can lookup our `run` function and call
// it.
run := instance.GetFunc(store, "run")
_, err = run.Call(store)
if err != nil {
	log.Fatal(err)
}

Output:

Hello from Go!

Index

Examples

Constants

This section is empty.

Variables

This section is empty.

Functions

func ModuleValidate 

func ModuleValidate(engine *Engine, wasm []byte) error

ModuleValidate validates whether `wasm` would be a valid wasm module according to the configuration in `store`

func Wat2Wasm 

func Wat2Wasm(wat string) ([]byte, error)

Wat2Wasm converts the text format of WebAssembly to the binary format.

Takes the text format in-memory as input, and returns either the binary encoding of the text format or an error if parsing fails.

Types

type AsExtern 

type AsExtern interface {
	AsExtern() C.wasmtime_extern_t
}

AsExtern is an interface for all types which can be imported or exported as an Extern

type AsExternType 

type AsExternType interface {
	AsExternType() *ExternType
}

AsExternType is an interface for all types which can be ExternType.

type Caller 

type Caller struct {
	// contains filtered or unexported fields
}

Caller is provided to host-defined functions when they're invoked from WebAssembly.

A `Caller` can be used for `Storelike` arguments to allow recursive execution or creation of wasm objects. Additionally `Caller` can be used to learn about the exports of the calling instance.

func (*Caller) Context 

func (c *Caller) Context() *C.wasmtime_context_t

Implementation of the `Storelike` interface for `Caller`.

func (*Caller) GetExport 

func (c *Caller) GetExport(name string) *Extern

GetExport gets an exported item from the caller's module.

May return `nil` if the export doesn't, if it's not a memory, if there isn't a caller, etc.

type Config 

type Config struct {
	// contains filtered or unexported fields
}

Config holds options used to create an Engine and customize its behavior.

Example (Fuel)

Example of limiting a WebAssembly function's runtime using "fuel consumption". 

config := wasmtime.NewConfig()
config.SetConsumeFuel(true)
engine := wasmtime.NewEngineWithConfig(config)
store := wasmtime.NewStore(engine)
err := store.SetFuel(10000)
if err != nil {
	log.Fatal(err)
}

// Compile and instantiate a small example with an infinite loop.
wasm, err := wasmtime.Wat2Wasm(`
	(module
	  (func $fibonacci (param $n i32) (result i32)
	    (if
	      (i32.lt_s (local.get $n) (i32.const 2))
	      (then (return (local.get $n)))
	    )
	    (i32.add
	      (call $fibonacci (i32.sub (local.get $n) (i32.const 1)))
	      (call $fibonacci (i32.sub (local.get $n) (i32.const 2)))
	    )
	  )
	  (export "fibonacci" (func $fibonacci))
	)
	`)
if err != nil {
	log.Fatal(err)
}
module, err := wasmtime.NewModule(store.Engine, wasm)
if err != nil {
	log.Fatal(err)
}
instance, err := wasmtime.NewInstance(store, module, []wasmtime.AsExtern{})
if err != nil {
	log.Fatal(err)
}

// Invoke `fibonacci` export with higher and higher numbers until we exhaust our fuel.
fibonacci := instance.GetFunc(store, "fibonacci")
if fibonacci == nil {
	log.Fatal("Failed to find function export `fibonacci`")
}
fuel := uint64(10000)
for n := 0; ; n++ {
	err := store.SetFuel(fuel)
	if err != nil {
		log.Fatal(err)
	}
	output, err := fibonacci.Call(store, n)
	if err != nil {
		break
	}
	fuelAfter, err := store.GetFuel()
	if err != nil {
		log.Fatal(err)
	}
	fmt.Printf("fib(%d) = %d [consumed %d fuel]\n", n, output, fuel-fuelAfter)
}

Output:

fib(0) = 0 [consumed 6 fuel]
fib(1) = 1 [consumed 6 fuel]
fib(2) = 1 [consumed 26 fuel]
fib(3) = 2 [consumed 46 fuel]
fib(4) = 3 [consumed 86 fuel]
fib(5) = 5 [consumed 146 fuel]
fib(6) = 8 [consumed 246 fuel]
fib(7) = 13 [consumed 406 fuel]
fib(8) = 21 [consumed 666 fuel]
fib(9) = 34 [consumed 1086 fuel]
fib(10) = 55 [consumed 1766 fuel]
fib(11) = 89 [consumed 2866 fuel]
fib(12) = 144 [consumed 4646 fuel]
fib(13) = 233 [consumed 7526 fuel]
Example (Interrupt)

Small example of how you can interrupt the execution of a wasm module to ensure that it doesn't run for too long. 

// Enable interruptable code via `Config` and then create an interrupt
// handle which we'll use later to interrupt running code.
config := wasmtime.NewConfig()
config.SetEpochInterruption(true)
engine := wasmtime.NewEngineWithConfig(config)
store := wasmtime.NewStore(engine)
store.SetEpochDeadline(1)

// Compile and instantiate a small example with an infinite loop.
wasm, err := wasmtime.Wat2Wasm(`
	(module
	  (func (export "run")
	    (loop
	      br 0)
	  )
	)
	`)
if err != nil {
	log.Fatal(err)
}
module, err := wasmtime.NewModule(store.Engine, wasm)
if err != nil {
	log.Fatal(err)
}
instance, err := wasmtime.NewInstance(store, module, []wasmtime.AsExtern{})
if err != nil {
	log.Fatal(err)
}
run := instance.GetFunc(store, "run")
if run == nil {
	log.Fatal("Failed to find function export `run`")
}

// Spin up a goroutine to send us an interrupt in a second
go func() {
	time.Sleep(1 * time.Second)
	fmt.Println("Interrupting!")
	engine.IncrementEpoch()
}()

fmt.Println("Entering infinite loop ...")
_, err = run.Call(store)
var trap *wasmtime.Trap
if !errors.As(err, &trap) {
	log.Fatal("Unexpected error")
}

fmt.Println("trap received...")
if !strings.Contains(trap.Message(), "wasm trap: interrupt") {
	log.Fatalf("Unexpected trap: %s", trap.Message())
}

Output:

Entering infinite loop ...
Interrupting!
trap received...
Example (Multi)

An example of enabling the multi-value feature of WebAssembly and interacting with multi-value functions. 

// Configure our `Store`, but be sure to use a `Config` that enables the
// wasm multi-value feature since it's not stable yet.
config := wasmtime.NewConfig()
config.SetWasmMultiValue(true)
store := wasmtime.NewStore(wasmtime.NewEngineWithConfig(config))

wasm, err := wasmtime.Wat2Wasm(`
	(module
	  (func $f (import "" "f") (param i32 i64) (result i64 i32))

	  (func $g (export "g") (param i32 i64) (result i64 i32)
	    (call $f (local.get 0) (local.get 1))
	  )

	  (func $round_trip_many
	    (export "round_trip_many")
	    (param i64 i64 i64 i64 i64 i64 i64 i64 i64 i64)
	    (result i64 i64 i64 i64 i64 i64 i64 i64 i64 i64)

	    local.get 0
	    local.get 1
	    local.get 2
	    local.get 3
	    local.get 4
	    local.get 5
	    local.get 6
	    local.get 7
	    local.get 8
	    local.get 9
	  )
	)
	`)
if err != nil {
	log.Fatal(err)
}
module, err := wasmtime.NewModule(store.Engine, wasm)
if err != nil {
	log.Fatal(err)
}

callback := wasmtime.WrapFunc(store, func(a int32, b int64) (int64, int32) {
	return b + 1, a + 1
})

instance, err := wasmtime.NewInstance(store, module, []wasmtime.AsExtern{callback})
if err != nil {
	log.Fatal(err)
}

g := instance.GetFunc(store, "g")

results, err := g.Call(store, 1, 3)
if err != nil {
	log.Fatal(err)
}
arr := results.([]wasmtime.Val)
a := arr[0].I64()
b := arr[1].I32()
fmt.Printf("> %d %d\n", a, b)

if a != 4 {
	log.Fatal("unexpected value for a")
}
if b != 2 {
	log.Fatal("unexpected value for b")
}

roundTripMany := instance.GetFunc(store, "round_trip_many")
results, err = roundTripMany.Call(store, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9)
if err != nil {
	log.Fatal(err)
}
arr = results.([]wasmtime.Val)

for i := 0; i < len(arr); i++ {
	fmt.Printf(" %d", arr[i].Get())
	if arr[i].I64() != int64(i) {
		log.Fatal("unexpected value for arr[i]")
	}
}

Output:

> 4 2
 0 1 2 3 4 5 6 7 8 9

func NewConfig 

func NewConfig() *Config

NewConfig creates a new `Config` with all default options configured.

func (*Config) CacheConfigLoad 

func (cfg *Config) CacheConfigLoad(path string) error

CacheConfigLoad enables compiled code caching for this `Config` using the settings specified in the configuration file `path`.

For more information about caching and configuration options see https://bytecodealliance.github.io/wasmtime/cli-cache.html

func (*Config) CacheConfigLoadDefault 

func (cfg *Config) CacheConfigLoadDefault() error

CacheConfigLoadDefault enables compiled code caching for this `Config` using the default settings configuration can be found.

For more information about caching see https://bytecodealliance.github.io/wasmtime/cli-cache.html

func (*Config) Close 

func (cfg *Config) Close()

Close will deallocate this config's state explicitly.

For more information see the documentation for engine.Close()

func (*Config) EnableCraneliftFlag 

func (cfg *Config) EnableCraneliftFlag(flag string)

EnableCraneliftFlag enables a target-specific flag in Cranelift.

This can be used, for example, to enable SSE4.2 on x86_64 hosts. Settings can be explored with `wasmtime settings` on the CLI.

For more information see the Rust documentation at https://docs.wasmtime.dev/api/wasmtime/struct.Config.html#method.cranelift_flag_enable

func (*Config) SetConsumeFuel 

func (cfg *Config) SetConsumeFuel(enabled bool)

SetConsumFuel configures whether fuel is enabled

func (*Config) SetCraneliftDebugVerifier 

func (cfg *Config) SetCraneliftDebugVerifier(enabled bool)

SetCraneliftDebugVerifier configures whether the cranelift debug verifier will be active when cranelift is used to compile wasm code.

func (*Config) SetCraneliftFlag 

func (cfg *Config) SetCraneliftFlag(name string, value string)

SetCraneliftFlag sets a target-specific flag in Cranelift to the specified value.

This can be used, for example, to enable SSE4.2 on x86_64 hosts. Settings can be explored with `wasmtime settings` on the CLI.

For more information see the Rust documentation at https://docs.wasmtime.dev/api/wasmtime/struct.Config.html#method.cranelift_flag_set

func (*Config) SetCraneliftOptLevel 

func (cfg *Config) SetCraneliftOptLevel(level OptLevel)

SetCraneliftOptLevel configures the cranelift optimization level for generated code

func (*Config) SetDebugInfo 

func (cfg *Config) SetDebugInfo(enabled bool)

SetDebugInfo configures whether dwarf debug information for JIT code is enabled

func (*Config) SetEpochInterruption 

func (cfg *Config) SetEpochInterruption(enable bool)

SetEpochInterruption enables epoch-based instrumentation of generated code to interrupt WebAssembly execution when the current engine epoch exceeds a defined threshold.

func (*Config) SetMaxWasmStack 

func (cfg *Config) SetMaxWasmStack(size int)

SetMaxWasmStack configures the maximum stack size, in bytes, that JIT code can use. The amount of stack space that wasm takes is always relative to the first invocation of wasm on the stack. Recursive calls with host frames in the middle will all need to fit within this setting. Note that this setting is not interpreted with 100% precision.

func (*Config) SetProfiler 

func (cfg *Config) SetProfiler(profiler ProfilingStrategy)

SetProfiler configures what profiler strategy to use for generated code

func (*Config) SetStrategy 

func (cfg *Config) SetStrategy(strat Strategy)

SetStrategy configures what compilation strategy is used to compile wasm code

func (*Config) SetTarget 

func (cfg *Config) SetTarget(target string) error

SetTarget configures the target triple that this configuration will produce machine code for.

This option defaults to the native host. Calling this method will additionally disable inference of the native features of the host (e.g. detection of SSE4.2 on x86_64 hosts). Native features can be reenabled with the `cranelift_flag_{set,enable}` properties.

For more information see the Rust documentation at https://docs.wasmtime.dev/api/wasmtime/struct.Config.html#method.config

func (*Config) SetWasmBulkMemory 

func (cfg *Config) SetWasmBulkMemory(enabled bool)

SetWasmBulkMemory configures whether the wasm bulk memory proposal is enabled

func (*Config) SetWasmMemory64 

func (cfg *Config) SetWasmMemory64(enabled bool)

SetWasmMemory64 configures whether the wasm memory64 proposal is enabled

func (*Config) SetWasmMultiMemory 

func (cfg *Config) SetWasmMultiMemory(enabled bool)

SetWasmMultiMemory configures whether the wasm multi memory proposal is enabled

func (*Config) SetWasmMultiValue 

func (cfg *Config) SetWasmMultiValue(enabled bool)

SetWasmMultiValue configures whether the wasm multi value proposal is enabled

func (*Config) SetWasmReferenceTypes 

func (cfg *Config) SetWasmReferenceTypes(enabled bool)

SetWasmReferenceTypes configures whether the wasm reference types proposal is enabled

func (*Config) SetWasmSIMD 

func (cfg *Config) SetWasmSIMD(enabled bool)

SetWasmSIMD configures whether the wasm SIMD proposal is enabled

func (*Config) SetWasmThreads 

func (cfg *Config) SetWasmThreads(enabled bool)

SetWasmThreads configures whether the wasm threads proposal is enabled

type Engine 

type Engine struct {
	// contains filtered or unexported fields
}

Engine is an instance of a wasmtime engine which is used to create a `Store`.

Engines are a form of global configuration for wasm compilations and modules and such.

func NewEngine 

func NewEngine() *Engine

NewEngine creates a new `Engine` with default configuration.

func NewEngineWithConfig 

func NewEngineWithConfig(config *Config) *Engine

NewEngineWithConfig creates a new `Engine` with the `Config` provided

Note that once a `Config` is passed to this method it cannot be used again.

func (*Engine) Close 

func (engine *Engine) Close()

Close will deallocate this engine's state explicitly.

By default state is cleaned up automatically when an engine is garbage collected but the Go GC. The Go GC, however, does not provide strict guarantees about finalizers especially in terms of timing. Additionally the Go GC is not aware of the full weight of an engine because it holds onto allocations in Wasmtime not tracked by the Go GC. For these reasons, it's recommended to where possible explicitly call this method and deallocate an engine to avoid relying on the Go GC.

This method will deallocate Wasmtime-owned state. Future use of the engine will panic because the Wasmtime state is no longer there.

Close can be called multiple times without error. Only the first time will deallocate resources.

func (*Engine) IncrementEpoch 

func (engine *Engine) IncrementEpoch()

IncrementEpoch will increase the current epoch number by 1 within the current engine which will cause any connected stores with their epoch deadline exceeded to now be interrupted.

This method is safe to call from any goroutine.

type Error 

type Error struct {
	// contains filtered or unexported fields
}

func (*Error) Close 

func (e *Error) Close()

Close will deallocate this error's state explicitly.

For more information see the documentation for engine.Close()

func (*Error) Error 

func (e *Error) Error() string

func (*Error) ExitStatus 

func (e *Error) ExitStatus() (int32, bool)

ExitStatus returns an `int32` exit status if this was a WASI-defined exit code. The `bool` returned indicates whether it was a WASI-defined exit or not.

type ExportType 

type ExportType struct {
	// contains filtered or unexported fields
}

ExportType is one of the exports component. A module defines a set of exports that become accessible to the host environment once the module has been instantiated.

func NewExportType 

func NewExportType(name string, ty AsExternType) *ExportType

NewExportType creates a new `ExportType` with the `name` and the type provided.

func (*ExportType) Close 

func (ty *ExportType) Close()

Close will deallocate this type's state explicitly.

For more information see the documentation for engine.Close()

func (*ExportType) Name 

func (ty *ExportType) Name() string

Name returns the name in the module this export type is exporting

func (*ExportType) Type 

func (ty *ExportType) Type() *ExternType

Type returns the type of item this export type expects

type Extern 

type Extern struct {
	// contains filtered or unexported fields
}

Extern is an external value, which is the runtime representation of an entity that can be imported or exported. It is an address denoting either a function instance, table instance, memory instance, or global instances in the shared store. Read more in [spec](https://webassembly.github.io/spec/core/exec/runtime.html#external-values)

func (*Extern) AsExtern 

func (e *Extern) AsExtern() C.wasmtime_extern_t

func (*Extern) Close 

func (e *Extern) Close()

Close will deallocate this extern's state explicitly.

For more information see the documentation for engine.Close()

func (*Extern) Func 

func (e *Extern) Func() *Func

Func returns a Func if this export is a function or nil otherwise

func (*Extern) Global 

func (e *Extern) Global() *Global

Global returns a Global if this export is a global or nil otherwise

func (*Extern) Memory 

func (e *Extern) Memory() *Memory

Memory returns a Memory if this export is a memory or nil otherwise

func (*Extern) Table 

func (e *Extern) Table() *Table

Table returns a Table if this export is a table or nil otherwise

func (*Extern) Type 

func (e *Extern) Type(store Storelike) *ExternType

Type returns the type of this export

type ExternType 

type ExternType struct {
	// contains filtered or unexported fields
}

ExternType means one of external types which classify imports and external values with their respective types.

func (*ExternType) AsExternType 

func (ty *ExternType) AsExternType() *ExternType

AsExternType returns this type itself

func (*ExternType) Close 

func (ty *ExternType) Close()

Close will deallocate this type's state explicitly.

For more information see the documentation for engine.Close()

func (*ExternType) FuncType 

func (ty *ExternType) FuncType() *FuncType

FuncType returns the underlying `FuncType` for this `ExternType` if it's a function type. Otherwise returns `nil`.

func (*ExternType) GlobalType 

func (ty *ExternType) GlobalType() *GlobalType

GlobalType returns the underlying `GlobalType` for this `ExternType` if it's a *global* type. Otherwise returns `nil`.

func (*ExternType) MemoryType 

func (ty *ExternType) MemoryType() *MemoryType

MemoryType returns the underlying `MemoryType` for this `ExternType` if it's a *memory* type. Otherwise returns `nil`.

func (*ExternType) TableType 

func (ty *ExternType) TableType() *TableType

TableType returns the underlying `TableType` for this `ExternType` if it's a *table* type. Otherwise returns `nil`.

type Frame 

type Frame struct {
	// contains filtered or unexported fields
}

Frame is one of activation frames which carry the return arity n of the respective function, hold the values of its locals (including arguments) in the order corresponding to their static local indices, and a reference to the function’s own module instance

func (*Frame) FuncIndex 

func (f *Frame) FuncIndex() uint32

FuncIndex returns the function index in the wasm module that this frame represents

func (*Frame) FuncName 

func (f *Frame) FuncName() *string

FuncName returns the name, if available, for this frame's function

func (*Frame) FuncOffset 

func (f *Frame) FuncOffset() uint

FuncOffset returns offset of this frame's instruction into the original function

func (*Frame) ModuleName 

func (f *Frame) ModuleName() *string

ModuleName returns the name, if available, for this frame's module

func (*Frame) ModuleOffset 

func (f *Frame) ModuleOffset() uint

ModuleOffset returns offset of this frame's instruction into the original module

type Func 

type Func struct {
	// contains filtered or unexported fields
}

Func is a function instance, which is the runtime representation of a function. It effectively is a closure of the original function over the runtime module instance of its originating module. The module instance is used to resolve references to other definitions during execution of the function. Read more in [spec](https://webassembly.github.io/spec/core/exec/runtime.html#function-instances)

func NewFunc 

func NewFunc(
	store Storelike,
	ty *FuncType,
	f func(*Caller, []Val) ([]Val, *Trap),
) *Func

NewFunc creates a new `Func` with the given `ty` which, when called, will call `f`

The `ty` given is the wasm type signature of the `Func` to create. When called the `f` callback receives two arguments. The first is a `Caller` to learn information about the calling context and the second is a list of arguments represented as a `Val`. The parameters are guaranteed to match the parameters types specified in `ty`.

The `f` callback is expected to produce one of two values. Results can be returned as an array of `[]Val`. The number and types of these results much match the `ty` given, otherwise the program will panic. The `f` callback can also produce a trap which will trigger trap unwinding in wasm, and the trap will be returned to the original caller.

If the `f` callback panics then the panic will be propagated to the caller as well.

func WrapFunc 

func WrapFunc(
	store Storelike,
	f interface{},
) *Func

WrapFunc wraps a native Go function, `f`, as a wasm `Func`.

This function differs from `NewFunc` in that it will determine the type signature of the wasm function given the input value `f`. The `f` value provided must be a Go function. It may take any number of the following types as arguments:

`int32` - a wasm `i32`

`int64` - a wasm `i64`

`float32` - a wasm `f32`

`float64` - a wasm `f64`

`*Caller` - information about the caller's instance

`*Func` - a wasm `funcref`

anything else - a wasm `externref`

The Go function may return any number of values. It can return any number of primitive wasm values (integers/floats), and the last return value may optionally be `*Trap`. If a `*Trap` returned is `nil` then the other values are returned from the wasm function. Otherwise the `*Trap` is returned and it's considered as if the host function trapped.

If the function `f` panics then the panic will be propagated to the caller.

func (*Func) AsExtern 

func (f *Func) AsExtern() C.wasmtime_extern_t

Implementation of the `AsExtern` interface for `Func`

func (*Func) Call 

func (f *Func) Call(store Storelike, args ...interface{}) (interface{}, error)

Call invokes this function with the provided `args`.

This variadic function must be invoked with the correct number and type of `args` as specified by the type of this function. This property is checked at runtime. Each `args` may have one of the following types:

`int32` - a wasm `i32`

`int64` - a wasm `i64`

`float32` - a wasm `f32`

`float64` - a wasm `f64`

`Val` - correspond to a wasm value

`*Func` - a wasm `funcref`

anything else - a wasm `externref`

This function will have one of three results:

1. If the function returns successfully, then the `interface{}` return argument will be the result of the function. If there were 0 results then this value is `nil`. If there was one result then this is that result. Otherwise if there were multiple results then `[]Val` is returned.

2. If this function invocation traps, then the returned `interface{}` value will be `nil` and a non-`nil` `*Trap` will be returned with information about the trap that happened.

3. If a panic in Go ends up happening somewhere, then this function will panic.

func (*Func) Type 

func (f *Func) Type(store Storelike) *FuncType

Type returns the type of this func

type FuncType 

type FuncType struct {
	// contains filtered or unexported fields
}

FuncType is one of function types which classify the signature of functions, mapping a vector of parameters to a vector of results. They are also used to classify the inputs and outputs of instructions.

func NewFuncType 

func NewFuncType(params, results []*ValType) *FuncType

NewFuncType creates a new `FuncType` with the `kind` provided

func (*FuncType) AsExternType 

func (ty *FuncType) AsExternType() *ExternType

AsExternType converts this type to an instance of `ExternType`

func (*FuncType) Close 

func (ty *FuncType) Close()

Close will deallocate this type's state explicitly.

For more information see the documentation for engine.Close()

func (*FuncType) Params 

func (ty *FuncType) Params() []*ValType

Params returns the parameter types of this function type

func (*FuncType) Results 

func (ty *FuncType) Results() []*ValType

Results returns the result types of this function type

type Global 

type Global struct {
	// contains filtered or unexported fields
}

Global is a global instance, which is the runtime representation of a global variable. It holds an individual value and a flag indicating whether it is mutable. Read more in [spec](https://webassembly.github.io/spec/core/exec/runtime.html#global-instances)

func NewGlobal 

func NewGlobal(
	store Storelike,
	ty *GlobalType,
	val Val,
) (*Global, error)

NewGlobal creates a new `Global` in the given `Store` with the specified `ty` and initial value `val`.

func (*Global) AsExtern 

func (g *Global) AsExtern() C.wasmtime_extern_t

func (*Global) Get 

func (g *Global) Get(store Storelike) Val

Get gets the value of this global

func (*Global) Set 

func (g *Global) Set(store Storelike, val Val) error

Set sets the value of this global

func (*Global) Type 

func (g *Global) Type(store Storelike) *GlobalType

Type returns the type of this global

type GlobalType 

type GlobalType struct {
	// contains filtered or unexported fields
}

GlobalType is a ValType, which classify global variables and hold a value and can either be mutable or immutable.

func NewGlobalType 

func NewGlobalType(content *ValType, mutable bool) *GlobalType

NewGlobalType creates a new `GlobalType` with the `kind` provided and whether it's `mutable` or not

func (*GlobalType) AsExternType 

func (ty *GlobalType) AsExternType() *ExternType

AsExternType converts this type to an instance of `ExternType`

func (*GlobalType) Close 

func (ty *GlobalType) Close()

Close will deallocate this type's state explicitly.

For more information see the documentation for engine.Close()

func (*GlobalType) Content 

func (ty *GlobalType) Content() *ValType

Content returns the type of value stored in this global

func (*GlobalType) Mutable 

func (ty *GlobalType) Mutable() bool

Mutable returns whether this global type is mutable or not

type ImportType 

type ImportType struct {
	// contains filtered or unexported fields
}

ImportType is one of the imports component A module defines a set of imports that are required for instantiation.

func NewImportType 

func NewImportType(module, name string, ty AsExternType) *ImportType

NewImportType creates a new `ImportType` with the given `module` and `name` and the type provided.

func (*ImportType) Close 

func (ty *ImportType) Close()

Close will deallocate this type's state explicitly.

For more information see the documentation for engine.Close()

func (*ImportType) Module 

func (ty *ImportType) Module() string

Module returns the name in the module this import type is importing

func (*ImportType) Name 

func (ty *ImportType) Name() *string

Name returns the name in the module this import type is importing.

Note that the returned string may be `nil` with the module linking proposal where this field is optional in the import type.

func (*ImportType) Type 

func (ty *ImportType) Type() *ExternType

Type returns the type of item this import type expects

type Instance 

type Instance struct {
	// contains filtered or unexported fields
}

Instance is an instantiated module instance. Once a module has been instantiated as an Instance, any exported function can be invoked externally via its function address funcaddr in the store S and an appropriate list val∗ of argument values.

func NewInstance 

func NewInstance(store Storelike, module *Module, imports []AsExtern) (*Instance, error)

NewInstance instantiates a WebAssembly `module` with the `imports` provided.

This function will attempt to create a new wasm instance given the provided imports. This can fail if the wrong number of imports are specified, the imports aren't of the right type, or for other resource-related issues.

This will also run the `start` function of the instance, returning an error if it traps.

func (*Instance) Exports 

func (instance *Instance) Exports(store Storelike) []*Extern

Exports returns a list of exports from this instance.

Each export is returned as a `*Extern` and lines up with the exports list of the associated `Module`.

func (*Instance) GetExport 

func (i *Instance) GetExport(store Storelike, name string) *Extern

GetExport attempts to find an export on this instance by `name`

May return `nil` if this instance has no export named `name`

func (*Instance) GetFunc 

func (i *Instance) GetFunc(store Storelike, name string) *Func

GetFunc attempts to find a function on this instance by `name`.

May return `nil` if this instance has no function named `name`, it is not a function, etc.

type Linker 

type Linker struct {
	Engine *Engine
	// contains filtered or unexported fields
}

Linker implements a wasmtime Linking module, which can link instantiated modules together. More details you can see [examples for C](https://bytecodealliance.github.io/wasmtime/examples-c-linking.html) or [examples for Rust](https://bytecodealliance.github.io/wasmtime/examples-rust-linking.html)

Example 
store := wasmtime.NewStore(wasmtime.NewEngine())

// Compile two wasm modules where the first references the second
wasm1, err := wasmtime.Wat2Wasm(`
	(module
	  (import "wasm2" "double" (func $double (param i32) (result i32)))
	  (func (export "double_and_add") (param i32 i32) (result i32)
	    local.get 0
	    call $double
	    local.get 1
	    i32.add
	  )
	)
	`)
if err != nil {
	log.Fatal(err)
}

wasm2, err := wasmtime.Wat2Wasm(`
	(module
	  (func (export "double") (param i32) (result i32)
	    local.get 0
	    i32.const 2
	    i32.mul
	  )
	)
	`)
if err != nil {
	log.Fatal(err)
}

// Next compile both modules
module1, err := wasmtime.NewModule(store.Engine, wasm1)
if err != nil {
	log.Fatal(err)
}
module2, err := wasmtime.NewModule(store.Engine, wasm2)
if err != nil {
	log.Fatal(err)
}

linker := wasmtime.NewLinker(store.Engine)

// The second module is instantiated first since it has no imports, and
// then we insert the instance back into the linker under the name
// the first module expects.
instance2, err := linker.Instantiate(store, module2)
if err != nil {
	log.Fatal(err)
}
err = linker.DefineInstance(store, "wasm2", instance2)
if err != nil {
	log.Fatal(err)
}

// And now we can instantiate our first module, executing the result
// afterwards
instance1, err := linker.Instantiate(store, module1)
if err != nil {
	log.Fatal(err)
}
doubleAndAdd := instance1.GetFunc(store, "double_and_add")
result, err := doubleAndAdd.Call(store, 2, 3)
if err != nil {
	log.Fatal(err)
}
fmt.Print(result.(int32))

Output:

7

func NewLinker 

func NewLinker(engine *Engine) *Linker

func (*Linker) AllowShadowing 

func (l *Linker) AllowShadowing(allow bool)

AllowShadowing configures whether names can be redefined after they've already been defined in this linker.

func (*Linker) Close 

func (l *Linker) Close()

Close will deallocate this linker's state explicitly.

For more information see the documentation for engine.Close()

func (*Linker) Define 

func (l *Linker) Define(store Storelike, module, name string, item AsExtern) error

Define defines a new item in this linker with the given module/name pair. Returns an error if shadowing is disallowed and the module/name is already defined.

func (*Linker) DefineFunc 

func (l *Linker) DefineFunc(store Storelike, module, name string, f interface{}) error

DefineFunc acts as a convenience wrapper to calling Define and WrapFunc.

Returns an error if shadowing is disabled and the name is already defined.

func (*Linker) DefineInstance 

func (l *Linker) DefineInstance(store Storelike, module string, instance *Instance) error

DefineInstance defines all exports of an instance provided under the module name provided.

Returns an error if shadowing is disabled and names are already defined.

func (*Linker) DefineModule 

func (l *Linker) DefineModule(store Storelike, name string, module *Module) error

DefineModule defines automatic instantiations of the module in this linker.

The `name` of the module is the name within the linker, and the `module` is the one that's being instantiated. This function automatically handles WASI Commands and Reactors for instantiation and initialization. For more information see the Rust documentation -- https://docs.wasmtime.dev/api/wasmtime/struct.Linker.html#method.module.

func (*Linker) DefineWasi 

func (l *Linker) DefineWasi() error

DefineWasi links a WASI module into this linker, ensuring that all exported functions are available for linking.

Returns an error if shadowing is disabled and names are already defined.

func (*Linker) FuncNew 

func (l *Linker) FuncNew(module, name string, ty *FuncType, f func(*Caller, []Val) ([]Val, *Trap)) error

FuncNew defines a function in this linker in the same style as `NewFunc`

Note that this function does not require a `Storelike`, which is intentional. This function can be used to insert store-independent functions into this linker which allows this linker to be used for instantiating modules in multiple different stores.

Returns an error if shadowing is disabled and the name is already defined.

func (*Linker) FuncWrap 

func (l *Linker) FuncWrap(module, name string, f interface{}) error

FuncWrap defines a function in this linker in the same style as `WrapFunc`

Note that this function does not require a `Storelike`, which is intentional. This function can be used to insert store-independent functions into this linker which allows this linker to be used for instantiating modules in multiple different stores.

Returns an error if shadowing is disabled and the name is already defined.

func (*Linker) Get 

func (l *Linker) Get(store Storelike, module, name string) *Extern

GetOneByName loads an item by name from this linker.

If the item isn't defined then nil is returned, otherwise the item is returned.

func (*Linker) GetDefault 

func (l *Linker) GetDefault(store Storelike, name string) (*Func, error)

GetDefault acquires the "default export" of the named module in this linker.

If there is no default item then an error is returned, otherwise the default function is returned.

For more information see the Rust documentation -- https://docs.wasmtime.dev/api/wasmtime/struct.Linker.html#method.get_default.

func (*Linker) Instantiate 

func (l *Linker) Instantiate(store Storelike, module *Module) (*Instance, error)

Instantiate instantiates a module with all imports defined in this linker.

Returns an error if the instance's imports couldn't be satisfied, had the wrong types, or if a trap happened executing the start function.

type Memory 

type Memory struct {
	// contains filtered or unexported fields
}

Memory instance is the runtime representation of a linear memory. It holds a vector of bytes and an optional maximum size, if one was specified at the definition site of the memory. Read more in [spec](https://webassembly.github.io/spec/core/exec/runtime.html#memory-instances) In wasmtime-go, you can get the vector of bytes by the unsafe pointer of memory from `Memory.Data()`, or go style byte slice from `Memory.UnsafeData()`

Example

An example of working with the Memory type to read/write wasm memory. 

// Create our `Store` context and then compile a module and create an
// instance from the compiled module all in one go.
store := wasmtime.NewStore(wasmtime.NewEngine())
wasm, err := wasmtime.Wat2Wasm(`
	(module
	  (memory (export "memory") 2 3)

	  (func (export "size") (result i32) (memory.size))
	  (func (export "load") (param i32) (result i32)
	    (i32.load8_s (local.get 0))
	  )
	  (func (export "store") (param i32 i32)
	    (i32.store8 (local.get 0) (local.get 1))
	  )

	  (data (i32.const 0x1000) "\01\02\03\04")
	)
	`)
if err != nil {
	log.Fatal(err)
}
module, err := wasmtime.NewModule(store.Engine, wasm)
if err != nil {
	log.Fatal(err)
}
instance, err := wasmtime.NewInstance(store, module, []wasmtime.AsExtern{})
if err != nil {
	log.Fatal(err)
}

// Load up our exports from the instance
memory := instance.GetExport(store, "memory").Memory()
sizeFn := instance.GetFunc(store, "size")
loadFn := instance.GetFunc(store, "load")
storeFn := instance.GetFunc(store, "store")

// some helper functions we'll use below
call32 := func(f *wasmtime.Func, args ...interface{}) int32 {
	ret, err := f.Call(store, args...)
	if err != nil {
		log.Fatal(err)
	}
	return ret.(int32)
}
call := func(f *wasmtime.Func, args ...interface{}) {
	_, err := f.Call(store, args...)
	if err != nil {
		log.Fatal(err)
	}
}
assertTraps := func(f *wasmtime.Func, args ...interface{}) {
	_, err := f.Call(store, args...)
	_, ok := err.(*wasmtime.Trap)
	if !ok {
		log.Fatal("expected a trap")
	}
}
assert := func(b bool) {
	if !b {
		log.Fatal("assertion failed")
	}
}

// Check the initial memory sizes/contents
assert(memory.Size(store) == 2)
assert(memory.DataSize(store) == 0x20000)
buf := memory.UnsafeData(store)

assert(buf[0] == 0)
assert(buf[0x1000] == 1)
assert(buf[0x1003] == 4)

assert(call32(sizeFn) == 2)
assert(call32(loadFn, 0) == 0)
assert(call32(loadFn, 0x1000) == 1)
assert(call32(loadFn, 0x1003) == 4)
assert(call32(loadFn, 0x1ffff) == 0)
assertTraps(loadFn, 0x20000)

// We can mutate memory as well
buf[0x1003] = 5
call(storeFn, 0x1002, 6)
assertTraps(storeFn, 0x20000, 0)

assert(buf[0x1002] == 6)
assert(buf[0x1003] == 5)
assert(call32(loadFn, 0x1002) == 6)
assert(call32(loadFn, 0x1003) == 5)

// And like wasm instructions, we can grow memory
_, err = memory.Grow(store, 1)
assert(err == nil)
assert(memory.Size(store) == 3)
assert(memory.DataSize(store) == 0x30000)

assert(call32(loadFn, 0x20000) == 0)
call(storeFn, 0x20000, 0)
assertTraps(loadFn, 0x30000)
assertTraps(storeFn, 0x30000, 0)

// Memory can fail to grow
_, err = memory.Grow(store, 1)
assert(err != nil)
_, err = memory.Grow(store, 0)
assert(err == nil)

// Ensure that `memory` lives long enough to cover all our usages of
// using its internal buffer we read from `UnsafeData()`
runtime.KeepAlive(memory)

// Finally we can also create standalone memories to get imported by
// wasm modules too.
memorytype := wasmtime.NewMemoryType(5, true, 5)
memory2, err := wasmtime.NewMemory(store, memorytype)
assert(err == nil)
assert(memory2.Size(store) == 5)
_, err = memory2.Grow(store, 1)
assert(err != nil)
_, err = memory2.Grow(store, 0)
assert(err == nil)

Output:

func NewMemory 

func NewMemory(store Storelike, ty *MemoryType) (*Memory, error)

NewMemory creates a new `Memory` in the given `Store` with the specified `ty`.

func (*Memory) AsExtern 

func (mem *Memory) AsExtern() C.wasmtime_extern_t

func (*Memory) Data 

func (mem *Memory) Data(store Storelike) unsafe.Pointer

Data returns the raw pointer in memory of where this memory starts

func (*Memory) DataSize 

func (mem *Memory) DataSize(store Storelike) uintptr

DataSize returns the size, in bytes, that `Data()` is valid for

func (*Memory) Grow 

func (mem *Memory) Grow(store Storelike, delta uint64) (uint64, error)

Grow grows this memory by `delta` pages

func (*Memory) Size 

func (mem *Memory) Size(store Storelike) uint64

Size returns the size, in wasm pages, of this memory

func (*Memory) Type 

func (mem *Memory) Type(store Storelike) *MemoryType

Type returns the type of this memory

func (*Memory) UnsafeData 

func (mem *Memory) UnsafeData(store Storelike) []byte

UnsafeData returns the raw memory backed by this `Memory` as a byte slice (`[]byte`).

This is not a safe method to call, hence the "unsafe" in the name. The byte slice returned from this function is not managed by the Go garbage collector. You need to ensure that `m`, the original `Memory`, lives longer than the `[]byte` returned.

Note that you may need to use `runtime.KeepAlive` to keep the original memory `m` alive for long enough while you're using the `[]byte` slice. If the `[]byte` slice is used after `m` is GC'd then that is undefined behavior.

type MemoryType 

type MemoryType struct {
	// contains filtered or unexported fields
}

MemoryType is one of Memory types which classify linear memories and their size range. The limits constrain the minimum and optionally the maximum size of a memory. The limits are given in units of page size.

func NewMemoryType 

func NewMemoryType(min uint32, has_max bool, max uint32) *MemoryType

NewMemoryType creates a new `MemoryType` with the limits on size provided

The `min` value is the minimum size, in WebAssembly pages, of this memory. The `has_max` boolean indicates whether a maximum size is present, and if so `max` is used as the maximum size of memory, in wasm pages.

Note that this will create a 32-bit memory type, the default outside of the memory64 proposal.

func NewMemoryType64 

func NewMemoryType64(min uint64, has_max bool, max uint64) *MemoryType

NewMemoryType64 creates a new 64-bit `MemoryType` with the provided limits

The `min` value is the minimum size, in WebAssembly pages, of this memory. The `has_max` boolean indicates whether a maximum size is present, and if so `max` is used as the maximum size of memory, in wasm pages.

Note that 64-bit memories are part of the memory64 WebAssembly proposal.

func (*MemoryType) AsExternType 

func (ty *MemoryType) AsExternType() *ExternType

AsExternType converts this type to an instance of `ExternType`

func (*MemoryType) Close 

func (ty *MemoryType) Close()

Close will deallocate this type's state explicitly.

For more information see the documentation for engine.Close()

func (*MemoryType) Is64 

func (ty *MemoryType) Is64() bool

Is64 returns whether this is a 64-bit memory or not.

func (*MemoryType) Maximum 

func (ty *MemoryType) Maximum() (bool, uint64)

Maximum returns the maximum size of this memory, in WebAssembly pages, if specified.

If the maximum size is not specified then `(false, 0)` is returned, otherwise `(true, N)` is returned where `N` is the listed maximum size of this memory.

func (*MemoryType) Minimum 

func (ty *MemoryType) Minimum() uint64

Minimum returns the minimum size of this memory, in WebAssembly pages

type Module 

type Module struct {
	// contains filtered or unexported fields
}

Module is a module which collects definitions for types, functions, tables, memories, and globals. In addition, it can declare imports and exports and provide initialization logic in the form of data and element segments or a start function. Modules organized WebAssembly programs as the unit of deployment, loading, and compilation.

Example (Serialize)

Small example of how to serialize a compiled wasm module, and then instantiate it from the compilation artifacts. 

// Configure the initial compilation environment.
engine := wasmtime.NewEngine()

// Compile the wasm module into an in-memory instance of a `Module`.
wasm, err := wasmtime.Wat2Wasm(`
	(module
	  (func $hello (import "" "hello"))
	  (func (export "run") (call $hello))
	)
	`)
if err != nil {
	log.Fatal(err)
}
module, err := wasmtime.NewModule(engine, wasm)
if err != nil {
	log.Fatal(err)
}
bytes, err := module.Serialize()
if err != nil {
	log.Fatal(err)
}

// Configure the initial compilation environment.
store := wasmtime.NewStore(wasmtime.NewEngine())

// Deserialize the compiled module.
module, err = wasmtime.NewModuleDeserialize(store.Engine, bytes)
if err != nil {
	log.Fatal(err)
}

// Here we handle the imports of the module, which in this case is our
// `helloFunc` callback.
helloFunc := wasmtime.WrapFunc(store, func() {
	fmt.Println("Calling back...")
	fmt.Println("> Hello World!")
})

// Once we've got that all set up we can then move to the instantiation
// phase, pairing together a compiled module as well as a set of imports.
// Note that this is where the wasm `start` function, if any, would run.
instance, err := wasmtime.NewInstance(store, module, []wasmtime.AsExtern{helloFunc})
if err != nil {
	log.Fatal(err)
}

// Next we poke around a bit to extract the `run` function from the module.
run := instance.GetFunc(store, "run")
if run == nil {
	log.Fatal("Failed to find function export `run`")
}

// And last but not least we can call it!
fmt.Println("Calling export...")
_, err = run.Call(store)
if err != nil {
	log.Fatal(err)
}

Output:

Calling export...
Calling back...
> Hello World!

func NewModule 

func NewModule(engine *Engine, wasm []byte) (*Module, error)

NewModule compiles a new `Module` from the `wasm` provided with the given configuration in `engine`.

func NewModuleDeserialize 

func NewModuleDeserialize(engine *Engine, encoded []byte) (*Module, error)

NewModuleDeserialize decodes and deserializes in-memory bytes previously produced by `module.Serialize()`.

This function does not take a WebAssembly binary as input. It takes as input the results of a previous call to `Serialize()`, and only takes that as input.

If deserialization is successful then a compiled module is returned, otherwise nil and an error are returned.

Note that to deserialize successfully the bytes provided must have been produced with an `Engine` that has the same compilation options as the provided engine, and from the same version of this library.

func NewModuleDeserializeFile 

func NewModuleDeserializeFile(engine *Engine, path string) (*Module, error)

NewModuleDeserializeFile is the same as `NewModuleDeserialize` except that the bytes are read from a file instead of provided as an argument.

func NewModuleFromFile 

func NewModuleFromFile(engine *Engine, file string) (*Module, error)

NewModuleFromFile reads the contents of the `file` provided and interprets them as either the text format or the binary format for WebAssembly.

Afterwards delegates to the `NewModule` constructor with the contents read.

func (*Module) Close 

func (m *Module) Close()

Close will deallocate this module's state explicitly.

For more information see the documentation for engine.Close()

func (*Module) Exports 

func (m *Module) Exports() []*ExportType

Exports returns a list of `ExportType` which are the items that will be exported by this module after instantiation.

func (*Module) Imports 

func (m *Module) Imports() []*ImportType

Imports returns a list of `ImportType` which are the items imported by this module and are required for instantiation

func (*Module) Serialize 

func (m *Module) Serialize() ([]byte, error)

Serialize will convert this in-memory compiled module into a list of bytes.

The purpose of this method is to extract an artifact which can be stored elsewhere from this `Module`. The returned bytes can, for example, be stored on disk or in an object store. The `NewModuleDeserialize` function can be used to deserialize the returned bytes at a later date to get the module back.

type OptLevel 

type OptLevel C.wasmtime_opt_level_t

OptLevel decides what degree of optimization wasmtime will perform on generated machine code 

const (
	// OptLevelNone will perform no optimizations
	OptLevelNone OptLevel = C.WASMTIME_OPT_LEVEL_NONE
	// OptLevelSpeed will optimize machine code to be as fast as possible
	OptLevelSpeed OptLevel = C.WASMTIME_OPT_LEVEL_SPEED
	// OptLevelSpeedAndSize will optimize machine code for speed, but also optimize
	// to be small, sometimes at the cost of speed.
	OptLevelSpeedAndSize OptLevel = C.WASMTIME_OPT_LEVEL_SPEED_AND_SIZE
)

type ProfilingStrategy 

type ProfilingStrategy C.wasmtime_profiling_strategy_t

ProfilingStrategy decides what sort of profiling to enable, if any. 

const (
	// ProfilingStrategyNone means no profiler will be used
	ProfilingStrategyNone ProfilingStrategy = C.WASMTIME_PROFILING_STRATEGY_NONE
	// ProfilingStrategyJitdump will use the "jitdump" linux support
	ProfilingStrategyJitdump ProfilingStrategy = C.WASMTIME_PROFILING_STRATEGY_JITDUMP
)

type Store 

type Store struct {

	// The `Engine` that this store uses for compilation and environment
	// settings.
	Engine *Engine
	// contains filtered or unexported fields
}

Store is a general group of wasm instances, and many objects must all be created with and reference the same `Store`

func NewStore 

func NewStore(engine *Engine) *Store

NewStore creates a new `Store` from the configuration provided in `engine`

func (*Store) Close 

func (store *Store) Close()

Close will deallocate this store's state explicitly.

For more information see the documentation for engine.Close()

func (*Store) Context 

func (store *Store) Context() *C.wasmtime_context_t

Implementation of the `Storelike` interface

func (*Store) GC 

func (store *Store) GC()

GC will clean up any `externref` values that are no longer actually referenced.

This function is not required to be called for correctness, it's only an optimization if desired to clean out any extra `externref` values.

func (*Store) GetFuel 

func (store *Store) GetFuel() (uint64, error)

GetFuel returns the amount of fuel remaining in this store.

If fuel consumption is not enabled via `Config.SetConsumeFuel` then this function will return an error. Otherwise this will retrieve the fuel remaining and return it.

Also note that fuel, if enabled, must be originally configured via `Store.SetFuel`.

func (*Store) Limiter 

func (store *Store) Limiter(
	memorySize int64,
	tableElements int64,
	instances int64,
	tables int64,
	memories int64,
)

Limiter provides limits for a store. Used by hosts to limit resource consumption of instances. Use negative value to keep the default value for the limit.

func (*Store) SetEpochDeadline 

func (store *Store) SetEpochDeadline(deadline uint64)

SetEpochDeadline will configure the relative deadline, from the current engine's epoch number, after which wasm code will be interrupted.

func (*Store) SetFuel 

func (store *Store) SetFuel(fuel uint64) error

SetFuel sets this store's fuel to the specified value.

For this method to work fuel consumption must be enabled via `Config.SetConsumeFuel`. By default a store starts with 0 fuel for wasm to execute with (meaning it will immediately trap). This function must be called for the store to have some fuel to allow WebAssembly to execute.

Note that at this time when fuel is entirely consumed it will cause wasm to trap. More usages of fuel are planned for the future.

If fuel is not enabled within this store then an error is returned.

func (*Store) SetWasi 

func (store *Store) SetWasi(wasi *WasiConfig)

SetWasi will configure the WASI state to use for instances within this `Store`.

The `wasi` argument cannot be reused for another `Store`, it's consumed by this function.

type Storelike 

type Storelike interface {
	// Returns the wasmtime context pointer this store is attached to.
	Context() *C.wasmtime_context_t
}

Storelike represents types that can be used to contextually reference a `Store`.

This interface is implemented by `*Store` and `*Caller` and is pervasively used throughout this library. You'll want to pass one of those two objects into functions that take a `Storelike`.

type Strategy 

type Strategy C.wasmtime_strategy_t

Strategy is the compilation strategies for wasmtime 

const (
	// StrategyAuto will let wasmtime automatically pick an appropriate compilation strategy
	StrategyAuto Strategy = C.WASMTIME_STRATEGY_AUTO
	// StrategyCranelift will force wasmtime to use the Cranelift backend
	StrategyCranelift Strategy = C.WASMTIME_STRATEGY_CRANELIFT
)

type Table 

type Table struct {
	// contains filtered or unexported fields
}

Table is a table instance, which is the runtime representation of a table.

It holds a vector of reference types and an optional maximum size, if one was specified in the table type at the table’s definition site. Read more in [spec](https://webassembly.github.io/spec/core/exec/runtime.html#table-instances)

func NewTable 

func NewTable(store Storelike, ty *TableType, init Val) (*Table, error)

NewTable creates a new `Table` in the given `Store` with the specified `ty`.

The `ty` must be a reference type (`funref` or `externref`) and `init` is the initial value for all table slots and must have the type specified by `ty`.

func (*Table) AsExtern 

func (t *Table) AsExtern() C.wasmtime_extern_t

func (*Table) Get 

func (t *Table) Get(store Storelike, idx uint32) (Val, error)

Get gets an item from this table from the specified index.

Returns an error if the index is out of bounds, or returns a value (which may be internally null) if the index is in bounds corresponding to the entry at the specified index.

func (*Table) Grow 

func (t *Table) Grow(store Storelike, delta uint32, init Val) (uint32, error)

Grow grows this table by the number of units specified, using the specified initializer value for new slots.

Returns an error if the table failed to grow, or the previous size of the table if growth was successful.

func (*Table) Set 

func (t *Table) Set(store Storelike, idx uint32, val Val) error

Set sets an item in this table at the specified index.

Returns an error if the index is out of bounds.

func (*Table) Size 

func (t *Table) Size(store Storelike) uint32

Size returns the size of this table in units of elements.

func (*Table) Type 

func (t *Table) Type(store Storelike) *TableType

Type returns the underlying type of this table

type TableType 

type TableType struct {
	// contains filtered or unexported fields
}

TableType is one of table types which classify tables over elements of element types within a size range.

func NewTableType 

func NewTableType(element *ValType, min uint32, has_max bool, max uint32) *TableType

NewTableType creates a new `TableType` with the `element` type provided as well as limits on its size.

The `min` value is the minimum size, in elements, of this table. The `has_max` boolean indicates whether a maximum size is present, and if so `max` is used as the maximum size of the table, in elements.

func (*TableType) AsExternType 

func (ty *TableType) AsExternType() *ExternType

AsExternType converts this type to an instance of `ExternType`

func (*TableType) Close 

func (ty *TableType) Close()

Close will deallocate this type's state explicitly.

For more information see the documentation for engine.Close()

func (*TableType) Element 

func (ty *TableType) Element() *ValType

Element returns the type of value stored in this table

func (*TableType) Maximum 

func (ty *TableType) Maximum() (bool, uint32)

Maximum returns the maximum size, in elements, of this table.

If no maximum size is listed then `(false, 0)` is returned, otherwise `(true, N)` is returned where `N` is the maximum size.

func (*TableType) Minimum 

func (ty *TableType) Minimum() uint32

Minimum returns the minimum size, in elements, of this table.

type Trap 

type Trap struct {
	// contains filtered or unexported fields
}

Trap is the trap instruction which represents the occurrence of a trap. Traps are bubbled up through nested instruction sequences, ultimately reducing the entire program to a single trap instruction, signalling abrupt termination.

func NewTrap 

func NewTrap(message string) *Trap

NewTrap creates a new `Trap` with the `name` and the type provided.

func (*Trap) Close 

func (t *Trap) Close()

Close will deallocate this type's state explicitly.

For more information see the documentation for engine.Close()

func (*Trap) Code 

func (t *Trap) Code() *TrapCode

Code returns the code of the `Trap` if it exists, nil otherwise.

func (*Trap) Error 

func (t *Trap) Error() string

func (*Trap) Frames 

func (t *Trap) Frames() []*Frame

Frames returns the wasm function frames that make up this trap

func (*Trap) Message 

func (t *Trap) Message() string

Message returns the message of the `Trap`

type TrapCode 

type TrapCode uint8

TrapCode is the code of an instruction trap. 

const (
	// StackOverflow: the current stack space was exhausted.
	StackOverflow TrapCode = iota
	// MemoryOutOfBounds: out-of-bounds memory access.
	MemoryOutOfBounds
	// HeapMisaligned: a wasm atomic operation was presented with a not-naturally-aligned linear-memory address.
	HeapMisaligned
	// TableOutOfBounds: out-of-bounds access to a table.
	TableOutOfBounds
	// IndirectCallToNull: indirect call to a null table entry.
	IndirectCallToNull
	// BadSignature: signature mismatch on indirect call.
	BadSignature
	// IntegerOverflow: an integer arithmetic operation caused an overflow.
	IntegerOverflow
	// IntegerDivisionByZero: integer division by zero.
	IntegerDivisionByZero
	// BadConversionToInteger: failed float-to-int conversion.
	BadConversionToInteger
	// UnreachableCodeReached: code that was supposed to have been unreachable was reached.
	UnreachableCodeReached
	// Interrupt: execution has been interrupted.
	Interrupt
	// OutOfFuel: Execution has run out of the configured fuel amount.
	OutOfFuel
)

type Val 

type Val struct {
	// contains filtered or unexported fields
}

Val is a primitive numeric value. Moreover, in the definition of programs, immutable sequences of values occur to represent more complex data, such as text strings or other vectors.

func ValExternref 

func ValExternref(val interface{}) Val

ValExternref converts a go value to a externref Val

Using `externref` is a way to pass arbitrary Go data into a WebAssembly module for it to store. Later, when you get a `Val`, you can extract the type with the `Externref()` method.

func ValF32 

func ValF32(val float32) Val

ValF32 converts a go float32 to a f32 Val

func ValF64 

func ValF64(val float64) Val

ValF64 converts a go float64 to a f64 Val

func ValFuncref 

func ValFuncref(f *Func) Val

ValFuncref converts a Func to a funcref Val

Note that `f` can be `nil` to represent a null `funcref`.

func ValI32 

func ValI32(val int32) Val

ValI32 converts a go int32 to a i32 Val

func ValI64 

func ValI64(val int64) Val

ValI64 converts a go int64 to a i64 Val

func (Val) Close 

func (v Val) Close()

Close will deallocate this value's state explicitly.

For more information see the documentation for engine.Close()

func (Val) Externref 

func (v Val) Externref() interface{}

Externref returns the underlying value if this is an `externref`, or panics.

Note that a null `externref` is returned as `nil`.

Example

Small example of how to use `externref`s. 

config := wasmtime.NewConfig()
config.SetWasmReferenceTypes(true)
store := wasmtime.NewStore(wasmtime.NewEngineWithConfig(config))
wasm, err := wasmtime.Wat2Wasm(`
	(module
	  (table $table (export "table") 10 externref)

	  (global $global (export "global") (mut externref) (ref.null extern))

	  (func (export "func") (param externref) (result externref)
	    local.get 0
	  )
	)
	`)
if err != nil {
	log.Fatal(err)
}
module, err := wasmtime.NewModule(store.Engine, wasm)
if err != nil {
	log.Fatal(err)
}
instance, err := wasmtime.NewInstance(store, module, []wasmtime.AsExtern{})
if err != nil {
	log.Fatal(err)
}
// Create a new `externref` value.
value := wasmtime.ValExternref("Hello, World!")
// The `externref`'s wrapped data should be the string "Hello, World!".
externRef := value.Externref()
if externRef != "Hello, World!" {
	log.Fatal("unexpected value")
}
// Lookup the `table` export.
table := instance.GetExport(store, "table").Table()
// Set `table[3]` to our `externref`.
err = table.Set(store, 3, value)
if err != nil {
	log.Fatal(err)
}
// `table[3]` should now be our `externref`.
tableValue, err := table.Get(store, 3)
if err != nil {
	log.Fatal(err)
}
if tableValue.Externref() != externRef {
	log.Fatal("unexpected value in table")
}
// Lookup the `global` export.
global := instance.GetExport(store, "global").Global()
// Set the global to our `externref`.
err = global.Set(store, value)
if err != nil {
	log.Fatal(err)
}
// Get the global, and it should return our `externref` again.
globalValue := global.Get(store)
if globalValue.Externref() != externRef {
	log.Fatal("unexpected value in global")
}
// Lookup the `func` export.
fn := instance.GetFunc(store, "func")
// And call it!
result, err := fn.Call(store, value)
if err != nil {
	log.Fatal(err)
}
// `func` returns the same reference we gave it, so `results` should be
// our `externref`.
if result != externRef {
	log.Fatal("unexpected value from func")
}

Output:

func (Val) F32 

func (v Val) F32() float32

F32 returns the underlying 32-bit float if this is an `f32`, or panics.

func (Val) F64 

func (v Val) F64() float64

F64 returns the underlying 64-bit float if this is an `f64`, or panics.

func (Val) Funcref 

func (v Val) Funcref() *Func

Funcref returns the underlying function if this is a `funcref`, or panics.

Note that a null `funcref` is returned as `nil`.

func (Val) Get 

func (v Val) Get() interface{}

Get returns the underlying 64-bit float if this is an `f64`, or panics.

func (Val) I32 

func (v Val) I32() int32

I32 returns the underlying 32-bit integer if this is an `i32`, or panics.

func (Val) I64 

func (v Val) I64() int64

I64 returns the underlying 64-bit integer if this is an `i64`, or panics.

func (Val) Kind 

func (v Val) Kind() ValKind

Kind returns the kind of value that this `Val` contains.

type ValKind 

type ValKind C.wasm_valkind_t

ValKind enumeration of different kinds of value types 

const (
	// KindI32 is the types i32 classify 32 bit integers. Integers are not inherently signed or unsigned, their interpretation is determined by individual operations.
	KindI32 ValKind = C.WASM_I32
	// KindI64 is the types i64 classify 64 bit integers. Integers are not inherently signed or unsigned, their interpretation is determined by individual operations.
	KindI64 ValKind = C.WASM_I64
	// KindF32 is the types f32 classify 32 bit floating-point data. They correspond to the respective binary floating-point representations, also known as single and double precision, as defined by the IEEE 754-2019 standard.
	KindF32 ValKind = C.WASM_F32
	// KindF64 is the types f64 classify 64 bit floating-point data. They correspond to the respective binary floating-point representations, also known as single and double precision, as defined by the IEEE 754-2019 standard.
	KindF64 ValKind = C.WASM_F64
	// TODO: Unknown
	KindExternref ValKind = C.WASM_ANYREF
	// KindFuncref is the infinite union of all function types.
	KindFuncref ValKind = C.WASM_FUNCREF
)

func (ValKind) String 

func (ty ValKind) String() string

String renders this kind as a string, similar to the `*.wat` format

type ValType 

type ValType struct {
	// contains filtered or unexported fields
}

ValType means one of the value types, which classify the individual values that WebAssembly code can compute with and the values that a variable accepts.

func NewValType 

func NewValType(kind ValKind) *ValType

NewValType creates a new `ValType` with the `kind` provided

func (*ValType) Close 

func (ty *ValType) Close()

Close will deallocate this type's state explicitly.

For more information see the documentation for engine.Close()

func (*ValType) Kind 

func (t *ValType) Kind() ValKind

Kind returns the corresponding `ValKind` for this `ValType`

func (*ValType) String 

func (t *ValType) String() string

Converts this `ValType` into a string according to the string representation of `ValKind`.

type WasiConfig 

type WasiConfig struct {
	// contains filtered or unexported fields
}
Example

An example of linking WASI to the runtime in order to interact with the system. It uses the WAT code from https://github.com/bytecodealliance/wasmtime/blob/main/docs/WASI-tutorial.md#web-assembly-text-example 

dir, err := os.MkdirTemp("", "out")
if err != nil {
	log.Fatal(err)
}
defer os.RemoveAll(dir)
stdoutPath := filepath.Join(dir, "stdout")

engine := wasmtime.NewEngine()

// Create our module
wasm, err := wasmtime.Wat2Wasm(`
	(module
	  ;; Import the required fd_write WASI function which will write the given io vectors to stdout
	  ;; The function signature for fd_write is:
	  ;; (File Descriptor, *iovs, iovs_len, nwritten) -> Returns number of bytes written
	  (import "wasi_snapshot_preview1" "fd_write" (func $fd_write (param i32 i32 i32 i32) (result i32)))

	  (memory 1)
	  (export "memory" (memory 0))

	  ;; Write 'hello world\n' to memory at an offset of 8 bytes
	  ;; Note the trailing newline which is required for the text to appear
	  (data (i32.const 8) "hello world\n")

	  (func $main (export "_start")
	    ;; Creating a new io vector within linear memory
	    (i32.store (i32.const 0) (i32.const 8))  ;; iov.iov_base - This is a pointer to the start of the 'hello world\n' string
	    (i32.store (i32.const 4) (i32.const 12))  ;; iov.iov_len - The length of the 'hello world\n' string

	    (call $fd_write
	      (i32.const 1) ;; file_descriptor - 1 for stdout
	      (i32.const 0) ;; *iovs - The pointer to the iov array, which is stored at memory location 0
	      (i32.const 1) ;; iovs_len - We're printing 1 string stored in an iov - so one.
	      (i32.const 20) ;; nwritten - A place in memory to store the number of bytes written
	    )
	    drop ;; Discard the number of bytes written from the top of the stack
	  )
	)
	`)
if err != nil {
	log.Fatal(err)
}
module, err := wasmtime.NewModule(engine, wasm)
if err != nil {
	log.Fatal(err)
}

// Create a linker with WASI functions defined within it
linker := wasmtime.NewLinker(engine)
err = linker.DefineWasi()
if err != nil {
	log.Fatal(err)
}

// Configure WASI imports to write stdout into a file, and then create
// a `Store` using this wasi configuration.
wasiConfig := wasmtime.NewWasiConfig()
wasiConfig.SetStdoutFile(stdoutPath)
store := wasmtime.NewStore(engine)
store.SetWasi(wasiConfig)
instance, err := linker.Instantiate(store, module)
if err != nil {
	log.Fatal(err)
}

// Run the function
nom := instance.GetFunc(store, "_start")
_, err = nom.Call(store)
if err != nil {
	log.Fatal(err)
}

// Print WASM stdout
out, err := os.ReadFile(stdoutPath)
if err != nil {
	log.Fatal(err)
}
fmt.Print(string(out))

Output:

hello world

func NewWasiConfig 

func NewWasiConfig() *WasiConfig

func (*WasiConfig) Close 

func (c *WasiConfig) Close()

Close will deallocate this WASI configuration's state explicitly.

For more information see the documentation for engine.Close()

func (*WasiConfig) InheritArgv 

func (c *WasiConfig) InheritArgv()

func (*WasiConfig) InheritEnv 

func (c *WasiConfig) InheritEnv()

func (*WasiConfig) InheritStderr 

func (c *WasiConfig) InheritStderr()

func (*WasiConfig) InheritStdin 

func (c *WasiConfig) InheritStdin()

func (*WasiConfig) InheritStdout 

func (c *WasiConfig) InheritStdout()

func (*WasiConfig) PreopenDir 

func (c *WasiConfig) PreopenDir(path, guestPath string) error

func (*WasiConfig) SetArgv 

func (c *WasiConfig) SetArgv(argv []string)

SetArgv will explicitly configure the argv for this WASI configuration. Note that this field can only be set, it cannot be read

func (*WasiConfig) SetEnv 

func (c *WasiConfig) SetEnv(keys, values []string)

SetEnv configures environment variables to be returned for this WASI configuration. The pairs provided must be an iterable list of key/value pairs of environment variables. Note that this field can only be set, it cannot be read

func (*WasiConfig) SetStderrFile 

func (c *WasiConfig) SetStderrFile(path string) error

func (*WasiConfig) SetStdinFile 

func (c *WasiConfig) SetStdinFile(path string) error

func (*WasiConfig) SetStdoutFile 

func (c *WasiConfig) SetStdoutFile(path string) error

Source Files

View all Source files

Directories

Path Synopsis
include
include/wasmtime
linux-aarch64
linux-x86_64
macos-aarch64
macos-x86_64
windows-x86_64

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