parse Java classfile

class/attribute.go

@@ -0,0 +1,5 @@
+package class
+
+type Attribute interface {
+
+}

class/classfile.go

@@ -0,0 +1,77 @@
+package class
+
+import (
+	"bytes"
+	"encoding/binary"
+	"encoding/hex"
+	"fmt"
+	"github.com/phith0n/zkar/commons"
+)
+
+type ClassFile struct {
+	MagicNumber []byte
+	MinorVersion uint16
+	MajorVersion uint16
+	ConstantPool []*Constant
+	AccessFlag uint16
+	ThisClassOffset uint16
+	SuperClassOffset uint16
+	InterfaceOffsetArray []uint16
+	Fields []*Field
+	Methods []*Method
+	Attributes []*Attribute
+}
+
+func (cf *ClassFile) readHeader(stream *commons.Stream) error {
+	bs, err := stream.ReadN(4)
+	if err != nil {
+		return fmt.Errorf("read magic number failed, no enough data in the stream")
+	}
+
+	if !bytes.Equal(bs, []byte("\xCA\xFE\xBA\xBE")) {
+		return fmt.Errorf("magic number %v is not equal to CAFEBABE", hex.EncodeToString(bs))
+	}
+
+	cf.MagicNumber = bs
+	bs, err = stream.ReadN(4)
+	if err != nil {
+		return fmt.Errorf("read minor and major version failed, no enough data in the stream")
+	}
+
+	cf.MinorVersion = binary.BigEndian.Uint16(bs[:2])
+	cf.MajorVersion = binary.BigEndian.Uint16(bs[2:])
+	return nil
+}
+
+func (cf *ClassFile) readConstantPool(stream *commons.Stream) error {
+	bs, err := stream.ReadN(2)
+	if err != nil {
+		return fmt.Errorf("read constant pool size failed, no enough data in the stream")
+	}
+
+	var size = binary.BigEndian.Uint16(bs)
+
+	// Note: Constant Pool index is start from 1, not 0
+	for i := uint16(1); i < size; i++ {
+		err = cf.readConstantPool(stream)
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func (cf *ClassFile) readConstant(stream *commons.Stream) error {
+	bs, err := stream.ReadN(1)
+	if err != nil {
+		return fmt.Errorf("read constant type failed, no enough data in the stream")
+	}
+
+	switch bs[0] {
+	case CONSTANT_UTF8_INFO:
+
+	}
+
+	return nil
+}

class/constant.go

@@ -0,0 +1,25 @@
+package class
+
+const (
+	CONSTANT_UTF8_INFO            = 1
+	CONSTANT_INTEGER_INFO         = 3
+	CONSTANT_FLOAT_INFO           = 4
+	CONSTANT_LONG_INFO            = 5
+	CONSTANT_DOUBLE_INFO          = 6
+	CONSTANT_CLASS_INFO           = 7
+	CONSTANT_STRING_INGFO         = 8
+	CONSTANT_FIELD_REF_INFO       = 9
+	CONSTANT_METHOD_REF_INFO      = 10
+	CONSTANT_INTERFACE_METHOD_REF = 11
+	CONSTANT_NAME_AND_TYPE_INFO   = 12
+	CONSTANT_METHOD_HANDLE_INFO   = 15
+	CONSTANT_METHOD_TYPE_INFO     = 16
+	CONSTANT_DYNAMIC_INFO         = 17
+	CONSTANT_INVOKE_DYNAMIC_INFO  = 18
+	CONSTANT_MODULE_INFO          = 19
+	CONSTANT_PACKAGE_INFO         = 20
+)
+
+type Constant interface {
+	Type() string
+}

class/field.go

@@ -0,0 +1,5 @@
+package class
+
+type Field struct {
+
+}

class/method.go

@@ -0,0 +1,5 @@
+package class
+
+type Method struct {
+
+}

class/parser.go

@@ -0,0 +1,14 @@
+package class
+
+import "github.com/phith0n/zkar/commons"
+
+func ParseClass(data []byte) (*ClassFile, error) {
+	stream := commons.NewStream(data)
+	classFile := new(ClassFile)
+	err := classFile.readHeader(stream)
+	if err != nil {
+		return nil, err
+	}
+
+	return classFile, nil
+}

class/parser_test.go

@@ -0,0 +1,18 @@
+package class
+
+import (
+	"github.com/phith0n/litter"
+	"github.com/stretchr/testify/require"
+	"io/ioutil"
+	"testing"
+)
+
+func TestParseClass(t *testing.T) {
+	data, err := ioutil.ReadFile("../testcases/classfile/TrainPrint.class")
+	require.Nil(t, err)
+
+	classFile, err := ParseClass(data)
+	require.Nil(t, err)
+
+	litter.Dump(classFile)
+}