working commit

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

@@ -0,0 +1,102 @@
+package binary
+
+import (
+	"bytes"
+	"fmt"
+
+	"github.com/tetratelabs/wabin/ieee754"
+	"github.com/tetratelabs/wabin/leb128"
+	"github.com/tetratelabs/wabin/wasm"
+)
+
+func decodeConstantExpression(r *bytes.Reader, features wasm.CoreFeatures) (*wasm.ConstantExpression, error) {
+	b, err := r.ReadByte()
+	if err != nil {
+		return nil, fmt.Errorf("read opcode: %v", err)
+	}
+
+	remainingBeforeData := int64(r.Len())
+	offsetAtData := r.Size() - remainingBeforeData
+
+	opcode := b
+	switch opcode {
+	case wasm.OpcodeI32Const:
+		// Treat constants as signed as their interpretation is not yet known per /RATIONALE.md
+		_, _, err = leb128.DecodeInt32(r)
+	case wasm.OpcodeI64Const:
+		// Treat constants as signed as their interpretation is not yet known per /RATIONALE.md
+		_, _, err = leb128.DecodeInt64(r)
+	case wasm.OpcodeF32Const:
+		_, err = ieee754.DecodeFloat32(r)
+	case wasm.OpcodeF64Const:
+		_, err = ieee754.DecodeFloat64(r)
+	case wasm.OpcodeGlobalGet:
+		_, _, err = leb128.DecodeUint32(r)
+	case wasm.OpcodeRefNull:
+		if err := features.RequireEnabled(wasm.CoreFeatureBulkMemoryOperations); err != nil {
+			return nil, fmt.Errorf("ref.null is not supported as %w", err)
+		}
+		reftype, err := r.ReadByte()
+		if err != nil {
+			return nil, fmt.Errorf("read reference type for ref.null: %w", err)
+		} else if reftype != wasm.RefTypeFuncref && reftype != wasm.RefTypeExternref {
+			return nil, fmt.Errorf("invalid type for ref.null: 0x%x", reftype)
+		}
+	case wasm.OpcodeRefFunc:
+		if err := features.RequireEnabled(wasm.CoreFeatureBulkMemoryOperations); err != nil {
+			return nil, fmt.Errorf("ref.func is not supported as %w", err)
+		}
+		// Parsing index.
+		_, _, err = leb128.DecodeUint32(r)
+	case wasm.OpcodeVecPrefix:
+		if err := features.RequireEnabled(wasm.CoreFeatureSIMD); err != nil {
+			return nil, fmt.Errorf("vector instructions are not supported as %w", err)
+		}
+		opcode, err = r.ReadByte()
+		if err != nil {
+			return nil, fmt.Errorf("read vector instruction opcode suffix: %w", err)
+		}
+
+		if opcode != wasm.OpcodeVecV128Const {
+			return nil, fmt.Errorf("invalid vector opcode for const expression: %#x", opcode)
+		}
+
+		remainingBeforeData = int64(r.Len())
+		offsetAtData = r.Size() - remainingBeforeData
+
+		n, err := r.Read(make([]byte, 16))
+		if err != nil {
+			return nil, fmt.Errorf("read vector const instruction immediates: %w", err)
+		} else if n != 16 {
+			return nil, fmt.Errorf("read vector const instruction immediates: needs 16 bytes but was %d bytes", n)
+		}
+	default:
+		return nil, fmt.Errorf("%v for const expression opt code: %#x", ErrInvalidByte, b)
+	}
+
+	if err != nil {
+		return nil, fmt.Errorf("read value: %v", err)
+	}
+
+	if b, err = r.ReadByte(); err != nil {
+		return nil, fmt.Errorf("look for end opcode: %v", err)
+	}
+
+	if b != wasm.OpcodeEnd {
+		return nil, fmt.Errorf("constant expression has been not terminated")
+	}
+
+	data := make([]byte, remainingBeforeData-int64(r.Len())-1)
+	if _, err := r.ReadAt(data, offsetAtData); err != nil {
+		return nil, fmt.Errorf("error re-buffering ConstantExpression.Data")
+	}
+
+	return &wasm.ConstantExpression{Opcode: opcode, Data: data}, nil
+}
+
+func encodeConstantExpression(expr *wasm.ConstantExpression) (ret []byte) {
+	ret = append(ret, expr.Opcode)
+	ret = append(ret, expr.Data...)
+	ret = append(ret, wasm.OpcodeEnd)
+	return
+}