b01effc8a9
While compilers should be conservative when targeting WebAssembly Core features, runtimes should be lenient as otherwise people need to constantly turn on all features. Currently, most examples have to turn on 2.0 features because compilers such as AssemblyScript and TinyGo use them by default. This matches the policy with the reality, and should make first time use easier. This top-levels an internal type as `api.CoreFeatures` and defaults to 2.0 as opposed to 1.0, our previous default. This is less cluttered than the excess of `WithXXX` methods we had prior to implementing all planned WebAssembly Core Specification 1.0 features. Finally, this backfills rationale as flat config types were a distinct decision even if feature set selection muddied the topic. Signed-off-by: Adrian Cole <adrian@tetrate.io>
68 lines
1.7 KiB
Go
68 lines
1.7 KiB
Go
package binary
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import (
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"bytes"
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"fmt"
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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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// decodeGlobal returns the api.Global decoded with the WebAssembly 1.0 (20191205) Binary Format.
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//
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// See https://www.w3.org/TR/2019/REC-wasm-core-1-20191205/#binary-global
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func decodeGlobal(r *bytes.Reader, enabledFeatures api.CoreFeatures) (*wasm.Global, error) {
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gt, err := decodeGlobalType(r)
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if err != nil {
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return nil, err
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}
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init, err := decodeConstantExpression(r, enabledFeatures)
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if err != nil {
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return nil, err
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}
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return &wasm.Global{Type: gt, Init: init}, nil
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}
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// decodeGlobalType returns the wasm.GlobalType decoded with the WebAssembly 1.0 (20191205) Binary Format.
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//
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// See https://www.w3.org/TR/2019/REC-wasm-core-1-20191205/#binary-globaltype
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func decodeGlobalType(r *bytes.Reader) (*wasm.GlobalType, error) {
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vt, err := decodeValueTypes(r, 1)
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if err != nil {
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return nil, fmt.Errorf("read value type: %w", err)
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}
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ret := &wasm.GlobalType{
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ValType: vt[0],
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}
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b, err := r.ReadByte()
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if err != nil {
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return nil, fmt.Errorf("read mutablity: %w", err)
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}
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switch mut := b; mut {
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case 0x00: // not mutable
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case 0x01: // mutable
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ret.Mutable = true
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default:
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return nil, fmt.Errorf("%w for mutability: %#x != 0x00 or 0x01", ErrInvalidByte, mut)
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}
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return ret, nil
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}
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// encodeGlobal returns the wasm.Global encoded in WebAssembly 1.0 (20191205) Binary Format.
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//
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// See https://www.w3.org/TR/2019/REC-wasm-core-1-20191205/#global-section%E2%91%A0
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func encodeGlobal(g *wasm.Global) (data []byte) {
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var mutable byte
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if g.Type.Mutable {
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mutable = 1
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}
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data = []byte{g.Type.ValType, mutable}
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data = append(data, encodeConstantExpression(g.Init)...)
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return
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}
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