f2b141ef9c
This updates to AssemblyScript 0.21 which no longer includes WASI. This updates guidance to use the shim, which I verified works. Signed-off-by: Adrian Cole <adrian@tetrate.io>
280 lines
9.3 KiB
Go
280 lines
9.3 KiB
Go
// Package assemblyscript contains Go-defined special functions imported by
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// AssemblyScript under the module name "env".
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//
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// # Special Functions
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//
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// AssemblyScript code import the below special functions when not using WASI.
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// Note: Sometimes only "abort" is imported.
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//
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// - "abort" - exits with 255 with an abort message written to
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// wazero.ModuleConfig WithStderr.
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// - "trace" - no output unless.
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// - "seed" - uses wazero.ModuleConfig WithRandSource as the source of seed
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// values.
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//
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// See https://www.assemblyscript.org/concepts.html#special-imports
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//
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// # Relationship to WASI
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//
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// AssemblyScript supports compiling JavaScript functions that use I/O, such
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// as `console.log("hello")`. However, WASI is not built-in to AssemblyScript.
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// Use the `wasi-shim` to compile if you get import errors.
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//
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// See https://github.com/AssemblyScript/wasi-shim#usage and
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// wasi_snapshot_preview1.Instantiate for more.
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package assemblyscript
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import (
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"context"
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"fmt"
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"io"
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"strconv"
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"strings"
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"unicode/utf16"
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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/internal/ieee754"
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"github.com/tetratelabs/wazero/internal/wasm"
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"github.com/tetratelabs/wazero/sys"
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)
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const (
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functionAbort = "abort"
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functionTrace = "trace"
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functionSeed = "seed"
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)
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// Instantiate instantiates the "env" module used by AssemblyScript into the
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// runtime default namespace.
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//
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// # Notes
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//
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// - Closing the wazero.Runtime has the same effect as closing the result.
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// - To add more functions to the "env" module, use FunctionExporter.
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// - To instantiate into another wazero.Namespace, use FunctionExporter.
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func Instantiate(ctx context.Context, r wazero.Runtime) (api.Closer, error) {
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builder := r.NewModuleBuilder("env")
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NewFunctionExporter().ExportFunctions(builder)
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return builder.Instantiate(ctx, r)
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}
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// FunctionExporter configures the functions in the "env" module used by
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// AssemblyScript.
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type FunctionExporter interface {
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// WithAbortMessageDisabled configures the AssemblyScript abort function to
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// discard any message.
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WithAbortMessageDisabled() FunctionExporter
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// WithTraceToStdout configures the AssemblyScript trace function to output
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// messages to Stdout, as configured by wazero.ModuleConfig WithStdout.
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WithTraceToStdout() FunctionExporter
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// WithTraceToStderr configures the AssemblyScript trace function to output
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// messages to Stderr, as configured by wazero.ModuleConfig WithStderr.
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//
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// Because of the potential volume of trace messages, it is often more
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// appropriate to use WithTraceToStdout instead.
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WithTraceToStderr() FunctionExporter
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// ExportFunctions builds functions to export with a wazero.ModuleBuilder
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// named "env".
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ExportFunctions(builder wazero.ModuleBuilder)
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}
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// NewFunctionExporter returns a FunctionExporter object with trace disabled.
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func NewFunctionExporter() FunctionExporter {
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return &functionExporter{abortFn: abortMessageEnabled, traceFn: traceDisabled}
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}
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type functionExporter struct {
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abortFn, traceFn *wasm.HostFunc
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}
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// WithAbortMessageDisabled implements FunctionExporter.WithAbortMessageDisabled
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func (e *functionExporter) WithAbortMessageDisabled() FunctionExporter {
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return &functionExporter{abortFn: abortMessageDisabled, traceFn: e.traceFn}
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}
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// WithTraceToStdout implements FunctionExporter.WithTraceToStdout
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func (e *functionExporter) WithTraceToStdout() FunctionExporter {
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return &functionExporter{abortFn: e.abortFn, traceFn: traceStdout}
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}
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// WithTraceToStderr implements FunctionExporter.WithTraceToStderr
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func (e *functionExporter) WithTraceToStderr() FunctionExporter {
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return &functionExporter{abortFn: e.abortFn, traceFn: traceStderr}
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}
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// ExportFunctions implements FunctionExporter.ExportFunctions
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func (e *functionExporter) ExportFunctions(builder wazero.ModuleBuilder) {
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builder.ExportFunction(functionAbort, e.abortFn)
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builder.ExportFunction(functionTrace, e.traceFn)
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builder.ExportFunction(functionSeed, seed)
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}
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// abort is called on unrecoverable errors. This is typically present in Wasm
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// compiled from AssemblyScript, if assertions are enabled or errors are
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// thrown.
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//
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// The implementation writes the message to stderr, unless
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// abortMessageDisabled, and closes the module with exit code 255.
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//
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// Here's the import in a user's module that ends up using this, in WebAssembly
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// 1.0 (MVP) Text Format:
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//
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// (import "env" "abort" (func $~lib/builtins/abort (param i32 i32 i32 i32)))
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//
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// See https://github.com/AssemblyScript/assemblyscript/blob/fa14b3b03bd4607efa52aaff3132bea0c03a7989/std/assembly/wasi/index.ts#L18
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var abortMessageEnabled = wasm.NewGoFunc(
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"abort", "~lib/builtins/abort",
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[]string{"message", "fileName", "lineNumber", "columnNumber"},
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abortWithMessage,
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)
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var abortMessageDisabled = abortMessageEnabled.MustGoFunc(abort)
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// abortWithMessage implements fnAbort
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func abortWithMessage(
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ctx context.Context, mod api.Module, message, fileName, lineNumber, columnNumber uint32,
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) {
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sysCtx := mod.(*wasm.CallContext).Sys
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mem := mod.Memory()
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// Don't panic if there was a problem reading the message
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if msg, msgOk := readAssemblyScriptString(ctx, mem, message); msgOk {
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if fn, fnOk := readAssemblyScriptString(ctx, mem, fileName); fnOk {
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_, _ = fmt.Fprintf(sysCtx.Stderr(), "%s at %s:%d:%d\n", msg, fn, lineNumber, columnNumber)
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}
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}
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abort(ctx, mod, message, fileName, lineNumber, columnNumber)
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}
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// abortWithMessage implements fnAbort ignoring the message.
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func abort(
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ctx context.Context, mod api.Module, message, fileName, lineNumber, columnNumber uint32,
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) {
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// AssemblyScript expects the exit code to be 255
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// See https://github.com/AssemblyScript/assemblyscript/blob/v0.20.13/tests/compiler/wasi/abort.js#L14
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exitCode := uint32(255)
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// Ensure other callers see the exit code.
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_ = mod.CloseWithExitCode(ctx, exitCode)
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// Prevent any code from executing after this function.
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panic(sys.NewExitError(mod.Name(), exitCode))
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}
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// traceDisabled ignores the input.
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var traceDisabled = traceStdout.WithWasm([]byte{wasm.OpcodeEnd})
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// traceStdout implements trace to the configured Stdout.
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var traceStdout = wasm.NewGoFunc(functionTrace, "~lib/builtins/trace",
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[]string{"message", "nArgs", "arg0", "arg1", "arg2", "arg3", "arg4"},
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func(
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ctx context.Context, mod api.Module, message uint32, nArgs uint32, arg0, arg1, arg2, arg3, arg4 float64,
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) {
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traceTo(ctx, mod, message, nArgs, arg0, arg1, arg2, arg3, arg4, mod.(*wasm.CallContext).Sys.Stdout())
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},
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)
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// traceStderr implements trace to the configured Stderr.
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var traceStderr = traceStdout.MustGoFunc(func(
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ctx context.Context, mod api.Module, message uint32, nArgs uint32, arg0, arg1, arg2, arg3, arg4 float64,
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) {
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traceTo(ctx, mod, message, nArgs, arg0, arg1, arg2, arg3, arg4, mod.(*wasm.CallContext).Sys.Stderr())
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})
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// traceTo implements the function "trace" in AssemblyScript. Ex.
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//
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// trace('Hello World!')
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//
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// Here's the import in a user's module that ends up using this, in WebAssembly
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// 1.0 (MVP) Text Format:
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//
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// (import "env" "trace" (func $~lib/builtins/trace (param i32 i32 f64 f64 f64 f64 f64)))
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//
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// See https://github.com/AssemblyScript/assemblyscript/blob/fa14b3b03bd4607efa52aaff3132bea0c03a7989/std/assembly/wasi/index.ts#L61
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func traceTo(
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ctx context.Context, mod api.Module, message uint32, nArgs uint32, arg0, arg1, arg2, arg3, arg4 float64,
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writer io.Writer,
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) {
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msg, ok := readAssemblyScriptString(ctx, mod.Memory(), message)
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if !ok {
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return // don't panic if unable to trace
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}
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var ret strings.Builder
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ret.WriteString("trace: ")
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ret.WriteString(msg)
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if nArgs >= 1 {
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ret.WriteString(" ")
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ret.WriteString(formatFloat(arg0))
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}
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if nArgs >= 2 {
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ret.WriteString(",")
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ret.WriteString(formatFloat(arg1))
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}
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if nArgs >= 3 {
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ret.WriteString(",")
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ret.WriteString(formatFloat(arg2))
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}
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if nArgs >= 4 {
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ret.WriteString(",")
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ret.WriteString(formatFloat(arg3))
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}
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if nArgs >= 5 {
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ret.WriteString(",")
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ret.WriteString(formatFloat(arg4))
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}
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ret.WriteByte('\n')
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_, _ = writer.Write([]byte(ret.String())) // don't crash if trace logging fails
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}
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func formatFloat(f float64) string {
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return strconv.FormatFloat(f, 'g', -1, 64)
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}
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// seed is called when the AssemblyScript's random number generator needs to be
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// seeded.
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//
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// Here's the import in a user's module that ends up using this, in WebAssembly
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// 1.0 (MVP) Text Format:
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//
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// (import "env" "seed" (func $~lib/builtins/seed (result f64)))
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//
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// See https://github.com/AssemblyScript/assemblyscript/blob/fa14b3b03bd4607efa52aaff3132bea0c03a7989/std/assembly/wasi/index.ts#L111
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var seed = wasm.NewGoFunc(functionSeed, "~lib/builtins/seed", []string{},
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func(mod api.Module) float64 {
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randSource := mod.(*wasm.CallContext).Sys.RandSource()
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v, err := ieee754.DecodeFloat64(randSource)
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if err != nil {
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panic(fmt.Errorf("error reading random seed: %w", err))
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}
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return v
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},
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)
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// readAssemblyScriptString reads a UTF-16 string created by AssemblyScript.
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func readAssemblyScriptString(ctx context.Context, mem api.Memory, offset uint32) (string, bool) {
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// Length is four bytes before pointer.
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byteCount, ok := mem.ReadUint32Le(ctx, offset-4)
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if !ok || byteCount%2 != 0 {
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return "", false
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}
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buf, ok := mem.Read(ctx, offset, byteCount)
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if !ok {
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return "", false
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}
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return decodeUTF16(buf), true
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}
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func decodeUTF16(b []byte) string {
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u16s := make([]uint16, len(b)/2)
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lb := len(b)
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for i := 0; i < lb; i += 2 {
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u16s[i/2] = uint16(b[i]) + (uint16(b[i+1]) << 8)
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}
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return string(utf16.Decode(u16s))
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}
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