939403c10b
This simplifies FunctionListener definition by making it possible to implement both interfaces without intermediate state. Passing the function definition to the before/after callbacks is the key. This also continues efforts towards Go 1.19 doc formatting. Signed-off-by: Adrian Cole <adrian@tetrate.io>
82 lines
3.0 KiB
Go
82 lines
3.0 KiB
Go
// Package emscripten contains Go-defined special functions imported by
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// Emscripten under the module name "env".
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//
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// Emscripten has many imports which are triggered on build flags. Use
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// FunctionExporter, instead of Instantiate, to define more "env" functions.
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//
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// # Relationship to WASI
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//
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// Emscripten typically requires wasi_snapshot_preview1 to implement exit.
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//
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// See wasi_snapshot_preview1.Instantiate and
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// https://github.com/emscripten-core/emscripten/wiki/WebAssembly-Standalone
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package emscripten
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import (
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"context"
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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/wasm"
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)
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// Instantiate instantiates the "env" module used by Emscripten 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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// Emscripten.
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type FunctionExporter interface {
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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{}
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}
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type functionExporter struct{}
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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(notifyMemoryGrowth.Name, notifyMemoryGrowth)
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}
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// emscriptenNotifyMemoryGrowth is called when wasm is compiled with
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// `-s ALLOW_MEMORY_GROWTH` and a "memory.grow" instruction succeeded.
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// The memoryIndex parameter will be zero until "multi-memory" is implemented.
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//
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// Note: This implementation is a no-op and can be overridden by users manually
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// by redefining the same function. wazero will likely implement a generic
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// memory growth hook obviating this as well.
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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" "emscripten_notify_memory_growth"
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// (func $emscripten_notify_memory_growth (param $memory_index i32)))
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//
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// See https://github.com/emscripten-core/emscripten/blob/3.1.16/system/lib/standalone/standalone.c#L118
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// and https://emscripten.org/docs/api_reference/emscripten.h.html#abi-functions
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const functionNotifyMemoryGrowth = "emscripten_notify_memory_growth"
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var notifyMemoryGrowth = &wasm.HostFunc{
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ExportNames: []string{functionNotifyMemoryGrowth},
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Name: functionNotifyMemoryGrowth,
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ParamTypes: []wasm.ValueType{wasm.ValueTypeI32},
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ParamNames: []string{"memory_index"},
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Code: &wasm.Code{IsHostFunction: true, Body: []byte{wasm.OpcodeEnd}},
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}
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