569 lines
14 KiB
Go
569 lines
14 KiB
Go
package nbt
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import (
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"bytes"
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"errors"
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"fmt"
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"io"
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"math"
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"reflect"
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)
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// Unmarshal decode binary NBT data and fill into v
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// This is a shortcut to `NewDecoder(bytes.NewReader(data)).Decode(v)`.
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func Unmarshal(data []byte, v interface{}) error {
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_, err := NewDecoder(bytes.NewReader(data)).Decode(v)
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return err
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}
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// Decode method decodes an NBT value from the reader underline the Decoder into v.
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// Internally try to handle all possible v by reflection,
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// but the type of v must matches the NBT value logically.
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// For example, you can decode an NBT value which root tag is TagCompound(0x0a)
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// into a struct or map, but not a string.
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//
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// This method also return tag name of the root tag.
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// In real world, it is often empty, but the API should allows you to get it when ever you want.
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func (d *Decoder) Decode(v interface{}) (string, error) {
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val := reflect.ValueOf(v)
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if val.Kind() != reflect.Ptr {
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return "", errors.New("nbt: non-pointer passed to Decode")
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}
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//start read NBT
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tagType, tagName, err := d.readTag()
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if err != nil {
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return tagName, fmt.Errorf("nbt: %w", err)
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}
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if c := d.checkCompressed(tagType); c != "" {
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return tagName, fmt.Errorf("nbt: unknown Tag, maybe compressed by %s, uncompress it first", c)
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}
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// We decode val not val.Elem because the NBTDecoder interface
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// test must be applied at the top level of the value.
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err = d.unmarshal(val, tagType)
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if err != nil {
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return tagName, fmt.Errorf("nbt: fail to decode tag %q: %w", tagName, err)
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}
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return tagName, nil
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}
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// checkCompressed check if the first byte is compress head
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func (d *Decoder) checkCompressed(head byte) (compress string) {
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switch head {
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case 0x1f:
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return "gzip"
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case 0x78:
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return "zlib"
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default:
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return ""
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}
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}
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// ErrEND error will be returned when reading a NBT with only Tag_End
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var ErrEND = errors.New("unexpected TAG_End")
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func (d *Decoder) unmarshal(val reflect.Value, tagType byte) error {
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u, val := indirect(val, tagType == TagEnd)
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if u != nil {
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return u.Decode(tagType, d.r)
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}
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switch tagType {
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default:
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return fmt.Errorf("unknown Tag 0x%02x", tagType)
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case TagEnd:
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return ErrEND
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case TagByte:
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value, err := d.r.ReadByte()
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if err != nil {
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return err
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}
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switch vk := val.Kind(); vk {
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default:
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return errors.New("cannot parse TagByte as " + vk.String())
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case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
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val.SetInt(int64(value))
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case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
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val.SetUint(uint64(value))
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case reflect.Interface:
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val.Set(reflect.ValueOf(value))
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}
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case TagShort:
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value, err := d.readInt16()
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if err != nil {
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return err
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}
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switch vk := val.Kind(); vk {
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default:
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return errors.New("cannot parse TagShort as " + vk.String())
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case reflect.Int, reflect.Int16, reflect.Int32, reflect.Int64:
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val.SetInt(int64(value))
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case reflect.Uint, reflect.Uint16, reflect.Uint32, reflect.Uint64:
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val.SetUint(uint64(value))
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case reflect.Interface:
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val.Set(reflect.ValueOf(value))
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}
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case TagInt:
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value, err := d.readInt32()
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if err != nil {
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return err
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}
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switch vk := val.Kind(); vk {
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default:
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return errors.New("cannot parse TagInt as " + vk.String())
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case reflect.Int, reflect.Int32, reflect.Int64:
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val.SetInt(int64(value))
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case reflect.Uint, reflect.Uint32, reflect.Uint64:
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val.SetUint(uint64(value))
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case reflect.Interface:
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val.Set(reflect.ValueOf(value))
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}
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case TagFloat:
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vInt, err := d.readInt32()
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if err != nil {
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return err
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}
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value := math.Float32frombits(uint32(vInt))
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switch vk := val.Kind(); vk {
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default:
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return errors.New("cannot parse TagFloat as " + vk.String())
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case reflect.Float32:
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val.Set(reflect.ValueOf(value))
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case reflect.Float64:
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val.Set(reflect.ValueOf(float64(value)))
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case reflect.Interface:
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val.Set(reflect.ValueOf(value))
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}
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case TagLong:
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value, err := d.readInt64()
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if err != nil {
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return err
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}
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switch vk := val.Kind(); vk {
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default:
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return errors.New("cannot parse TagLong as " + vk.String())
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case reflect.Int, reflect.Int64:
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val.SetInt(int64(value))
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case reflect.Uint, reflect.Uint64:
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val.SetUint(uint64(value))
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case reflect.Interface:
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val.Set(reflect.ValueOf(value))
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}
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case TagDouble:
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vInt, err := d.readInt64()
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if err != nil {
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return err
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}
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value := math.Float64frombits(uint64(vInt))
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switch vk := val.Kind(); vk {
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default:
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return errors.New("cannot parse TagDouble as " + vk.String())
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case reflect.Float64:
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val.Set(reflect.ValueOf(value))
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case reflect.Interface:
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val.Set(reflect.ValueOf(value))
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}
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case TagString:
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s, err := d.readString()
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if err != nil {
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return err
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}
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switch vk := val.Kind(); vk {
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default:
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return errors.New("cannot parse TagString as " + vk.String())
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case reflect.String:
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val.SetString(s)
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case reflect.Interface:
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val.Set(reflect.ValueOf(s))
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}
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case TagByteArray:
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aryLen, err := d.readInt32()
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if err != nil {
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return err
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}
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if aryLen < 0 {
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return errors.New("byte array len less than 0")
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}
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ba := make([]byte, aryLen)
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if _, err = io.ReadFull(d.r, ba); err != nil {
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return err
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}
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switch vt := val.Type(); {
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default:
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return errors.New("cannot parse TagByteArray to " + vt.String() + ", use []byte in this instance")
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case vt == reflect.TypeOf(ba):
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val.SetBytes(ba)
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case vt.Kind() == reflect.Interface:
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val.Set(reflect.ValueOf(ba))
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}
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case TagIntArray:
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aryLen, err := d.readInt32()
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if err != nil {
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return err
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}
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vt := val.Type() //receiver must be []int or []int32
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if vt.Kind() == reflect.Interface {
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vt = reflect.TypeOf([]int32{}) // pass
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} else if vt.Kind() != reflect.Slice {
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return errors.New("cannot parse TagIntArray to " + vt.String() + ", it must be a slice")
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} else if tk := val.Type().Elem().Kind(); tk != reflect.Int && tk != reflect.Int32 {
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return errors.New("cannot parse TagIntArray to " + vt.String())
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}
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buf := reflect.MakeSlice(vt, int(aryLen), int(aryLen))
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for i := 0; i < int(aryLen); i++ {
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value, err := d.readInt32()
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if err != nil {
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return err
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}
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buf.Index(i).SetInt(int64(value))
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}
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val.Set(buf)
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case TagLongArray:
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aryLen, err := d.readInt32()
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if err != nil {
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return err
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}
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vt := val.Type() //receiver must be []int or []int64
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if vt.Kind() == reflect.Interface {
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vt = reflect.TypeOf([]int64{}) // pass
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} else if vt.Kind() != reflect.Slice {
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return errors.New("cannot parse TagLongArray to " + vt.String() + ", it must be a slice")
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} else if val.Type().Elem().Kind() != reflect.Int64 {
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return errors.New("cannot parse TagLongArray to " + vt.String())
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}
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buf := reflect.MakeSlice(vt, int(aryLen), int(aryLen))
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for i := 0; i < int(aryLen); i++ {
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value, err := d.readInt64()
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if err != nil {
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return err
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}
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buf.Index(i).SetInt(value)
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}
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val.Set(buf)
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case TagList:
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listType, err := d.r.ReadByte()
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if err != nil {
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return err
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}
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listLen, err := d.readInt32()
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if err != nil {
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return err
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}
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if listLen < 0 {
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return errors.New("list length less than 0")
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}
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// If we need parse TAG_List into slice, make a new with right length.
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// Otherwise if we need parse into array, we check if len(array) are enough.
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var buf reflect.Value
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vk := val.Kind()
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switch vk {
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default:
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return errors.New("cannot parse TagList as " + vk.String())
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case reflect.Interface:
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buf = reflect.ValueOf(make([]interface{}, listLen))
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case reflect.Slice:
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buf = reflect.MakeSlice(val.Type(), int(listLen), int(listLen))
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case reflect.Array:
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if vl := val.Len(); vl < int(listLen) {
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return fmt.Errorf(
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"TagList has len %d, but array %v only has len %d",
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listLen, val.Type(), vl)
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}
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buf = val
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}
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for i := 0; i < int(listLen); i++ {
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if err := d.unmarshal(buf.Index(i), listType); err != nil {
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return err
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}
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}
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if vk != reflect.Array {
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val.Set(buf)
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}
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case TagCompound:
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switch vk := val.Kind(); vk {
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default:
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return errors.New("cannot parse TagCompound as " + vk.String())
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case reflect.Struct:
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tinfo := getTypeInfo(val.Type())
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for {
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tt, tn, err := d.readTag()
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if err != nil {
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return err
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}
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if tt == TagEnd {
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break
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}
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field := tinfo.findIndexByName(tn)
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if field != -1 {
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err = d.unmarshal(val.Field(field), tt)
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if err != nil {
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return fmt.Errorf("fail to decode tag %q: %w", tn, err)
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}
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} else {
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if err := d.rawRead(tt); err != nil {
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return err
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}
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}
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}
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case reflect.Map:
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if val.Type().Key().Kind() != reflect.String {
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return errors.New("cannot parse TagCompound as " + val.Type().String())
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}
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if val.IsNil() {
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val.Set(reflect.MakeMap(val.Type()))
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}
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for {
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tt, tn, err := d.readTag()
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if err != nil {
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return err
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}
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if tt == TagEnd {
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break
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}
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v := reflect.New(val.Type().Elem())
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if err = d.unmarshal(v.Elem(), tt); err != nil {
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return fmt.Errorf("fail to decode tag %q: %w", tn, err)
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}
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val.SetMapIndex(reflect.ValueOf(tn), v.Elem())
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}
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case reflect.Interface:
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buf := make(map[string]interface{})
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for {
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tt, tn, err := d.readTag()
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if err != nil {
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return err
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}
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if tt == TagEnd {
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break
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}
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var value interface{}
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if err = d.unmarshal(reflect.ValueOf(&value).Elem(), tt); err != nil {
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return fmt.Errorf("fail to decode tag %q: %w", tn, err)
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}
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buf[tn] = value
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}
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val.Set(reflect.ValueOf(buf))
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}
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}
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return nil
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}
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// indirect walks down v allocating pointers as needed,
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// until it gets to a non-pointer.
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// If it encounters an NBTDecoder, indirect stops and returns that.
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// If decodingNull is true, indirect stops at the first settable pointer so it
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// can be set to nil.
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//
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// This function is copied and modified from encoding/json
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func indirect(v reflect.Value, decodingNull bool) (NBTDecoder, reflect.Value) {
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v0 := v
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haveAddr := false
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// If v is a named type and is addressable,
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// start with its address, so that if the type has pointer methods,
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// we find them.
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if v.Kind() != reflect.Ptr && v.Type().Name() != "" && v.CanAddr() {
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haveAddr = true
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v = v.Addr()
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}
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for {
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// Load value from interface, but only if the result will be
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// usefully addressable.
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if v.Kind() == reflect.Interface && !v.IsNil() {
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e := v.Elem()
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if e.Kind() == reflect.Ptr && !e.IsNil() && (!decodingNull || e.Elem().Kind() == reflect.Ptr) {
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haveAddr = false
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v = e
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continue
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}
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}
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if v.Kind() != reflect.Ptr {
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break
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}
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if decodingNull && v.CanSet() {
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break
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}
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// Prevent infinite loop if v is an interface pointing to its own address:
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// var v interface{}
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// v = &v
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if v.Elem().Kind() == reflect.Interface && v.Elem().Elem() == v {
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v = v.Elem()
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break
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}
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if v.IsNil() {
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v.Set(reflect.New(v.Type().Elem()))
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}
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if v.Type().NumMethod() > 0 && v.CanInterface() {
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if u, ok := v.Interface().(NBTDecoder); ok {
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return u, reflect.Value{}
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}
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}
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if haveAddr {
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v = v0 // restore original value after round-trip Value.Addr().Elem()
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haveAddr = false
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} else {
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v = v.Elem()
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}
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}
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return nil, v
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}
|
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|
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// rawRead read and discard a value
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func (d *Decoder) rawRead(tagType byte) error {
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var buf [8]byte
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switch tagType {
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default:
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return fmt.Errorf("unknown to read 0x%02x", tagType)
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case TagByte:
|
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_, err := d.r.ReadByte()
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return err
|
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case TagString:
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_, err := d.readString()
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return err
|
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case TagShort:
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_, err := io.ReadFull(d.r, buf[:2])
|
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return err
|
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case TagInt, TagFloat:
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_, err := io.ReadFull(d.r, buf[:4])
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return err
|
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case TagLong, TagDouble:
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_, err := io.ReadFull(d.r, buf[:8])
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return err
|
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case TagByteArray:
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aryLen, err := d.readInt32()
|
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if err != nil {
|
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return err
|
|
}
|
|
|
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if _, err = io.CopyN(io.Discard, d.r, int64(aryLen)); err != nil {
|
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return err
|
|
}
|
|
case TagIntArray:
|
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aryLen, err := d.readInt32()
|
|
if err != nil {
|
|
return err
|
|
}
|
|
for i := 0; i < int(aryLen); i++ {
|
|
if _, err := d.readInt32(); err != nil {
|
|
return err
|
|
}
|
|
}
|
|
|
|
case TagLongArray:
|
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aryLen, err := d.readInt32()
|
|
if err != nil {
|
|
return err
|
|
}
|
|
for i := 0; i < int(aryLen); i++ {
|
|
if _, err := d.readInt64(); err != nil {
|
|
return err
|
|
}
|
|
}
|
|
|
|
case TagList:
|
|
listType, err := d.r.ReadByte()
|
|
if err != nil {
|
|
return err
|
|
}
|
|
listLen, err := d.readInt32()
|
|
if err != nil {
|
|
return err
|
|
}
|
|
for i := 0; i < int(listLen); i++ {
|
|
if err := d.rawRead(listType); err != nil {
|
|
return err
|
|
}
|
|
}
|
|
case TagCompound:
|
|
for {
|
|
tt, _, err := d.readTag()
|
|
if err != nil {
|
|
return err
|
|
}
|
|
if tt == TagEnd {
|
|
break
|
|
}
|
|
err = d.rawRead(tt)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
}
|
|
}
|
|
return nil
|
|
}
|
|
|
|
func (d *Decoder) readTag() (tagType byte, tagName string, err error) {
|
|
tagType, err = d.r.ReadByte()
|
|
if err != nil {
|
|
return
|
|
}
|
|
|
|
if tagType != TagEnd { //Read Tag
|
|
tagName, err = d.readString()
|
|
}
|
|
return
|
|
}
|
|
|
|
func (d *Decoder) readInt16() (int16, error) {
|
|
var data [2]byte
|
|
_, err := io.ReadFull(d.r, data[:])
|
|
return int16(data[0])<<8 | int16(data[1]), err
|
|
}
|
|
|
|
func (d *Decoder) readInt32() (int32, error) {
|
|
var data [4]byte
|
|
_, err := io.ReadFull(d.r, data[:])
|
|
return int32(data[0])<<24 | int32(data[1])<<16 |
|
|
int32(data[2])<<8 | int32(data[3]), err
|
|
}
|
|
|
|
func (d *Decoder) readInt64() (int64, error) {
|
|
var data [8]byte
|
|
_, err := io.ReadFull(d.r, data[:])
|
|
return int64(data[0])<<56 | int64(data[1])<<48 |
|
|
int64(data[2])<<40 | int64(data[3])<<32 |
|
|
int64(data[4])<<24 | int64(data[5])<<16 |
|
|
int64(data[6])<<8 | int64(data[7]), err
|
|
}
|
|
|
|
func (d *Decoder) readString() (string, error) {
|
|
length, err := d.readInt16()
|
|
if err != nil {
|
|
return "", err
|
|
} else if length < 0 {
|
|
return "", errors.New("string length less than 0")
|
|
}
|
|
|
|
var str string
|
|
if length > 0 {
|
|
buf := make([]byte, length)
|
|
_, err = io.ReadFull(d.r, buf)
|
|
str = string(buf)
|
|
}
|
|
return str, err
|
|
}
|