working commit

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

@@ -0,0 +1,94 @@
+package binary
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+
+	"github.com/tetratelabs/wabin/leb128"
+	"github.com/tetratelabs/wabin/wasm"
+)
+
+// dataSegmentPrefix represents three types of data segments.
+//
+// https://www.w3.org/TR/2022/WD-wasm-core-2-20220419/binary/modules.html#data-section
+type dataSegmentPrefix = uint32
+
+const (
+	// dataSegmentPrefixActive is the prefix for the version 1.0 compatible
+	// data segment, which is classified as "active" in 2.0.
+	dataSegmentPrefixActive dataSegmentPrefix = 0x0
+	// dataSegmentPrefixPassive prefixes the "passive" data segment as in
+	// version 2.0 specification.
+	dataSegmentPrefixPassive dataSegmentPrefix = 0x1
+	// dataSegmentPrefixActiveWithMemoryIndex is the active prefix with memory
+	//index encoded which is defined for future use as of 2.0.
+	dataSegmentPrefixActiveWithMemoryIndex dataSegmentPrefix = 0x2
+)
+
+func decodeDataSegment(r *bytes.Reader, features wasm.CoreFeatures) (*wasm.DataSegment, error) {
+	dataSegmentPrefix, _, err := leb128.DecodeUint32(r)
+	if err != nil {
+		return nil, fmt.Errorf("read data segment prefix: %w", err)
+	}
+
+	if dataSegmentPrefix != dataSegmentPrefixActive {
+		if err := features.RequireEnabled(wasm.CoreFeatureBulkMemoryOperations); err != nil {
+			return nil, fmt.Errorf("non-zero prefix for data segment is invalid as %w", err)
+		}
+	}
+
+	var expr *wasm.ConstantExpression
+	switch dataSegmentPrefix {
+	case dataSegmentPrefixActive,
+		dataSegmentPrefixActiveWithMemoryIndex:
+		// Active data segment as in
+		// https://www.w3.org/TR/2022/WD-wasm-core-2-20220419/binary/modules.html#data-section
+		if dataSegmentPrefix == 0x2 {
+			d, _, err := leb128.DecodeUint32(r)
+			if err != nil {
+				return nil, fmt.Errorf("read memory index: %v", err)
+			} else if d != 0 {
+				return nil, fmt.Errorf("memory index must be zero but was %d", d)
+			}
+		}
+
+		expr, err = decodeConstantExpression(r, features)
+		if err != nil {
+			return nil, fmt.Errorf("read offset expression: %v", err)
+		}
+	case dataSegmentPrefixPassive:
+		// Passive data segment doesn't need const expr nor memory index encoded.
+		// https://www.w3.org/TR/2022/WD-wasm-core-2-20220419/binary/modules.html#data-section
+	default:
+		return nil, fmt.Errorf("invalid data segment prefix: 0x%x", dataSegmentPrefix)
+	}
+
+	vs, _, err := leb128.DecodeUint32(r)
+	if err != nil {
+		return nil, fmt.Errorf("get the size of vector: %v", err)
+	}
+
+	b := make([]byte, vs)
+	if _, err := io.ReadFull(r, b); err != nil {
+		return nil, fmt.Errorf("read bytes for init: %v", err)
+	}
+
+	return &wasm.DataSegment{
+		OffsetExpression: expr,
+		Init:             b,
+	}, nil
+}
+
+func encodeDataSegment(d *wasm.DataSegment) (ret []byte) {
+	if d.OffsetExpression == nil {
+		ret = append(ret, leb128.EncodeInt32(int32(dataSegmentPrefixPassive))...)
+	} else {
+		// Currently multiple memories are not supported.
+		ret = append(ret, leb128.EncodeInt32(int32(dataSegmentPrefixActive))...)
+		ret = append(ret, encodeConstantExpression(d.OffsetExpression)...)
+	}
+	ret = append(ret, leb128.EncodeUint32(uint32(len(d.Init)))...)
+	ret = append(ret, d.Init...)
+	return
+}