working commit

vendor/github.com/tetratelabs/wabin/binary/global.go

@@ -0,0 +1,66 @@
+package binary
+
+import (
+	"bytes"
+	"fmt"
+
+	"github.com/tetratelabs/wabin/wasm"
+)
+
+// decodeGlobal returns the wasm.Global decoded with the WebAssembly Binary Format.
+//
+// See https://www.w3.org/TR/2019/REC-wasm-core-1-20191205/#binary-global
+func decodeGlobal(r *bytes.Reader, features wasm.CoreFeatures) (*wasm.Global, error) {
+	gt, err := decodeGlobalType(r)
+	if err != nil {
+		return nil, err
+	}
+
+	init, err := decodeConstantExpression(r, features)
+	if err != nil {
+		return nil, err
+	}
+
+	return &wasm.Global{Type: gt, Init: init}, nil
+}
+
+// decodeGlobalType returns the wasm.GlobalType decoded with the WebAssembly 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 nil, fmt.Errorf("read value type: %w", err)
+	}
+
+	ret := &wasm.GlobalType{
+		ValType: vt[0],
+	}
+
+	b, err := r.ReadByte()
+	if err != nil {
+		return nil, fmt.Errorf("read mutablity: %w", err)
+	}
+
+	switch mut := b; mut {
+	case 0x00: // not mutable
+	case 0x01: // mutable
+		ret.Mutable = true
+	default:
+		return nil, fmt.Errorf("%w for mutability: %#x != 0x00 or 0x01", ErrInvalidByte, mut)
+	}
+	return ret, nil
+}
+
+// encodeGlobal returns the wasm.Global encoded in WebAssembly Binary Format.
+//
+// See https://www.w3.org/TR/2019/REC-wasm-core-1-20191205/#global-section%E2%91%A0
+func encodeGlobal(g *wasm.Global) (data []byte) {
+	var mutable byte
+	if g.Type.Mutable {
+		mutable = 1
+	}
+	data = []byte{g.Type.ValType, mutable}
+	data = append(data, encodeConstantExpression(g.Init)...)
+	return
+}