127 lines
4.4 KiB
Go
127 lines
4.4 KiB
Go
package main
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import (
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"context"
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_ "embed"
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"fmt"
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"log"
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"github.com/tetratelabs/wazero"
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"github.com/tetratelabs/wazero/api"
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)
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// main implements functions with multiple returns values, using both an
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// approach portable with any WebAssembly 1.0 runtime, as well one dependent
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// on the "multiple-results" feature.
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//
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// The portable approach uses parameters to return additional results. The
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// parameter value is a memory offset to write the next value. This is the same
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// approach used by WASI.
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// - resultOffsetWasmFunctions
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// - resultOffsetHostFunctions
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//
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// See https://github.com/WebAssembly/WASI/blob/snapshot-01/phases/snapshot/docs.md
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//
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// Another approach is to enable the "multiple-results" feature. While
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// "multiple-results" is not yet a W3C recommendation, most WebAssembly
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// runtimes support it by default, and it is include in the draft of 2.0.
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// - multiValueWasmFunctions
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// - multiValueHostFunctions
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//
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// See https://github.com/WebAssembly/spec/blob/wg-2.0.draft1/proposals/multi-value/Overview.md
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func main() {
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// Choose the context to use for function calls.
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ctx := context.Background()
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// Create a new WebAssembly Runtime.
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r := wazero.NewRuntime(ctx)
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defer r.Close(ctx) // This closes everything this Runtime created.
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// Add a module that uses offset parameters for multiple results defined in WebAssembly.
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wasm, err := resultOffsetWasmFunctions(ctx, r)
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if err != nil {
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log.Panicln(err)
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}
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// wazero enables WebAssembly 1.0 by default. Opt-in to other features:
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runtimeWithMultiValue := wazero.NewRuntimeWithConfig(
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ctx, wazero.NewRuntimeConfig().WithFeatureMultiValue(true),
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// ^^ Note: WebAssembly 2.0 (WithWasmCore2) includes "multi-value".
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)
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// Add a module that uses multiple results values
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// ... defined in WebAssembly.
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wasmWithMultiValue, err := multiValueWasmFunctions(ctx, runtimeWithMultiValue)
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if err != nil {
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log.Panicln(err)
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}
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// ... defined in Go.
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multiValueFromImportedHost, err := multiValueFromImportedHostWasmFunctions(ctx, runtimeWithMultiValue)
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if err != nil {
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log.Panicln(err)
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}
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// Call the function from each module and print the results to the console.
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for _, mod := range []api.Module{wasm, wasmWithMultiValue, multiValueFromImportedHost} {
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getAge := mod.ExportedFunction("call_get_age")
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results, err := getAge.Call(ctx)
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if err != nil {
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log.Panicln(err)
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}
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fmt.Printf("%s: age=%d\n", mod.Name(), results[0])
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}
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}
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// resultOffsetWasm was generated by the following:
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//
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// cd testdata; wat2wasm --debug-names result_offset.wat
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//
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//go:embed testdata/result_offset.wasm
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var resultOffsetWasm []byte
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// resultOffsetWasmFunctions are the WebAssembly equivalent of the Go-defined
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// resultOffsetHostFunctions. The source is in testdata/result_offset.wat
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func resultOffsetWasmFunctions(ctx context.Context, r wazero.Runtime) (api.Module, error) {
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return r.InstantiateModuleFromBinary(ctx, resultOffsetWasm)
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}
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// multiValueWasm was generated by the following:
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//
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// cd testdata; wat2wasm --debug-names multi_value.wat
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//
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//go:embed testdata/multi_value.wasm
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var multiValueWasm []byte
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// multiValueWasmFunctions are the WebAssembly equivalent of the Go-defined
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// multiValueHostFunctions. The source is in testdata/multi_value.wat
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func multiValueWasmFunctions(ctx context.Context, r wazero.Runtime) (api.Module, error) {
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return r.InstantiateModuleFromBinary(ctx, multiValueWasm)
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}
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// multiValueWasm was generated by the following:
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//
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// cd testdata; wat2wasm --debug-names multi_value_imported.wat
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//
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//go:embed testdata/multi_value_imported.wasm
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var multiValueFromImportedHostWasm []byte
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// multiValueFromImportedHostWasmFunctions return the WebAssembly which imports the Go-defined "get_age" function.
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// The imported "get_age" function returns multiple results. The source is in testdata/multi_value_imported.wat
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func multiValueFromImportedHostWasmFunctions(ctx context.Context, r wazero.Runtime) (api.Module, error) {
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// Instantiate the host module with the exported `get_age` function which returns multiple results.
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if _, err := r.NewModuleBuilder("multi-value/host").
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// Define a function that returns two results
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ExportFunction("get_age", func() (age uint64, errno uint32) {
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age = 37
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errno = 0
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return
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}).Instantiate(ctx, r); err != nil {
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return nil, err
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}
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// Then, creates the module which imports the `get_age` function from the `multi-value/host` module above.
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return r.InstantiateModuleFromBinary(ctx, multiValueFromImportedHostWasm)
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}
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