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package binary
import (
"bytes"
"fmt"
"github.com/tetratelabs/wazero/api"
"github.com/tetratelabs/wazero/internal/wasm"
)
// decodeGlobal returns the api.Global decoded with the WebAssembly 1.0 (20191205) Binary Format.
//
// See https://www.w3.org/TR/2019/REC-wasm-core-1-20191205/#binary-global
func decodeGlobal(r *bytes.Reader, enabledFeatures api.CoreFeatures, ret *wasm.Global) (err error) {
ret.Type, err = decodeGlobalType(r)
if err != nil {
return err
}
err = decodeConstantExpression(r, enabledFeatures, &ret.Init)
return
}
// decodeGlobalType returns the wasm.GlobalType decoded with the WebAssembly 1.0 (20191205) Binary Format.
//
// See https://www.w3.org/TR/2019/REC-wasm-core-1-20191205/#binary-globaltype
func decodeGlobalType(r *bytes.Reader) (wasm.GlobalType, error) {
vt, err := decodeValueTypes(r, 1)
if err != nil {
return wasm.GlobalType{}, fmt.Errorf("read value type: %w", err)
}
ret := wasm.GlobalType{
ValType: vt[0],
}
b, err := r.ReadByte()
if err != nil {
return wasm.GlobalType{}, fmt.Errorf("read mutablity: %w", err)
}
switch mut := b; mut {
case 0x00: // not mutable
case 0x01: // mutable
ret.Mutable = true
default:
return wasm.GlobalType{}, fmt.Errorf("%w for mutability: %#x != 0x00 or 0x01", ErrInvalidByte, mut)
}
return ret, nil
}
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