03bfa31928
This removes tedium in our examples and docs by using `Runtime.Close` instead of tracking everything. Internal tests still track too much, but anyway at least this stops suggesting others should do it. This also changes our examples to use log.PanicXX so that the line number goes into the console output. Signed-off-by: Adrian Cole <adrian@tetrate.io>
113 lines
3.5 KiB
Go
113 lines
3.5 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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"os"
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"github.com/tetratelabs/wazero"
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"github.com/tetratelabs/wazero/api"
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"github.com/tetratelabs/wazero/wasi"
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)
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// greetWasm was compiled using `tinygo build -o greet.wasm -scheduler=none --no-debug -target=wasi greet.go`
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//go:embed testdata/greet.wasm
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var greetWasm []byte
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// main shows how to interact with a WebAssembly function that was compiled
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// from TinyGo.
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//
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// See README.md for a full description.
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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()
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defer r.Close(ctx) // This closes everything this Runtime created.
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// Instantiate a Go-defined module named "env" that exports a function to
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// log to the console.
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_, err := r.NewModuleBuilder("env").
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ExportFunction("log", logString).
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Instantiate(ctx)
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if err != nil {
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log.Panicln(err)
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}
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// Note: testdata/greet.go doesn't use WASI, but TinyGo needs it to
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// implement functions such as panic.
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if _, err = wasi.InstantiateSnapshotPreview1(ctx, r); err != nil {
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log.Panicln(err)
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}
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// Instantiate a WebAssembly module that imports the "log" function defined
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// in "env" and exports "memory" and functions we'll use in this example.
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mod, err := r.InstantiateModuleFromCode(ctx, greetWasm)
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if err != nil {
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log.Panicln(err)
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}
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// Get references to WebAssembly functions we'll use in this example.
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greet := mod.ExportedFunction("greet")
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greeting := mod.ExportedFunction("greeting")
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// These are undocumented, but exported. See tinygo-org/tinygo#2788
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malloc := mod.ExportedFunction("malloc")
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free := mod.ExportedFunction("free")
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// Let's use the argument to this main function in Wasm.
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name := os.Args[1]
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nameSize := uint64(len(name))
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// Instead of an arbitrary memory offset, use TinyGo's allocator. Notice
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// there is nothing string-specific in this allocation function. The same
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// function could be used to pass binary serialized data to Wasm.
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results, err := malloc.Call(ctx, nameSize)
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if err != nil {
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log.Panicln(err)
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}
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namePtr := results[0]
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// This pointer is managed by TinyGo, but TinyGo is unaware of external usage.
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// So, we have to free it when finished
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defer free.Call(ctx, namePtr)
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// The pointer is a linear memory offset, which is where we write the name.
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if !mod.Memory().Write(ctx, uint32(namePtr), []byte(name)) {
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log.Panicf("Memory.Write(%d, %d) out of range of memory size %d",
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namePtr, nameSize, mod.Memory().Size(ctx))
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}
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// Now, we can call "greet", which reads the string we wrote to memory!
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_, err = greet.Call(ctx, namePtr, nameSize)
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if err != nil {
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log.Panicln(err)
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}
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// Finally, we get the greeting message "greet" printed. This shows how to
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// read-back something allocated by TinyGo.
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ptrSize, err := greeting.Call(ctx, namePtr, nameSize)
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if err != nil {
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log.Panicln(err)
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}
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// Note: This pointer is still owned by TinyGo, so don't try to free it!
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greetingPtr := uint32(ptrSize[0] >> 32)
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greetingSize := uint32(ptrSize[0])
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// The pointer is a linear memory offset, which is where we write the name.
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if bytes, ok := mod.Memory().Read(ctx, greetingPtr, greetingSize); !ok {
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log.Panicf("Memory.Read(%d, %d) out of range of memory size %d",
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greetingPtr, greetingSize, mod.Memory().Size(ctx))
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} else {
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fmt.Println("go >>", string(bytes))
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}
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}
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func logString(ctx context.Context, m api.Module, offset, byteCount uint32) {
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buf, ok := m.Memory().Read(ctx, offset, byteCount)
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if !ok {
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log.Panicf("Memory.Read(%d, %d) out of range", offset, byteCount)
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}
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fmt.Println(string(buf))
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}
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