/
encoding.go
424 lines (383 loc) · 12.3 KB
/
encoding.go
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package nbt
import (
"errors"
"math"
"unsafe"
)
// Encoding is an encoding variant of NBT. In general, there are three different encodings of NBT, which are
// all the same except for the way basic types are written.
type Encoding interface {
Int16(r *offsetReader) (int16, error)
Int32(r *offsetReader) (int32, error)
Int64(r *offsetReader) (int64, error)
Float32(r *offsetReader) (float32, error)
Float64(r *offsetReader) (float64, error)
String(r *offsetReader) (string, error)
WriteInt16(w *offsetWriter, x int16) error
WriteInt32(w *offsetWriter, x int32) error
WriteInt64(w *offsetWriter, x int64) error
WriteFloat32(w *offsetWriter, x float32) error
WriteFloat64(w *offsetWriter, x float64) error
WriteString(w *offsetWriter, x string) error
}
// NetworkLittleEndian is the variable sized integer implementation of NBT. It is otherwise the same as the
// normal little endian NBT. The NetworkLittleEndian format limits the total bytes of NBT that may be read. If
// the limit is hit, the reading operation will fail immediately.
var NetworkLittleEndian networkLittleEndian
// LittleEndian is the fixed size little endian implementation of NBT. It is the format typically used for
// writing Minecraft (Bedrock Edition) world saves.
var LittleEndian littleEndian
// BigEndian is the fixed size big endian implementation of NBT. It is the original implementation, and is
// used only on Minecraft Java Edition.
var BigEndian bigEndian
var _ = BigEndian
var _ = LittleEndian
var _ = NetworkLittleEndian
type networkLittleEndian struct{ littleEndian }
// WriteInt32 ...
func (networkLittleEndian) WriteInt32(w *offsetWriter, x int32) error {
ux := uint32(x) << 1
if x < 0 {
ux = ^ux
}
for ux >= 0x80 {
if err := w.WriteByte(byte(ux) | 0x80); err != nil {
return FailedWriteError{Op: "WriteInt32", Off: w.off}
}
ux >>= 7
}
if err := w.WriteByte(byte(ux)); err != nil {
return FailedWriteError{Op: "WriteInt32", Off: w.off}
}
return nil
}
// WriteInt64 ...
func (networkLittleEndian) WriteInt64(w *offsetWriter, x int64) error {
ux := uint64(x) << 1
if x < 0 {
ux = ^ux
}
for ux >= 0x80 {
if err := w.WriteByte(byte(ux) | 0x80); err != nil {
return FailedWriteError{Op: "WriteInt64", Off: w.off}
}
ux >>= 7
}
if err := w.WriteByte(byte(ux)); err != nil {
return FailedWriteError{Op: "WriteInt64", Off: w.off}
}
return nil
}
// WriteString ...
func (networkLittleEndian) WriteString(w *offsetWriter, x string) error {
if len(x) > math.MaxInt16 {
return InvalidStringError{Off: w.off, String: x, Err: errors.New("string length exceeds maximum length prefix")}
}
ux := uint32(len(x))
for ux >= 0x80 {
if err := w.WriteByte(byte(ux) | 0x80); err != nil {
return FailedWriteError{Op: "WriteString", Off: w.off}
}
ux >>= 7
}
if err := w.WriteByte(byte(ux)); err != nil {
return FailedWriteError{Op: "WriteString", Off: w.off}
}
// Use unsafe conversion from a string to a byte slice to prevent copying.
if _, err := w.Write(*(*[]byte)(unsafe.Pointer(&x))); err != nil {
return FailedWriteError{Op: "WriteString", Off: w.off}
}
return nil
}
// Int32 ...
func (networkLittleEndian) Int32(r *offsetReader) (int32, error) {
var ux uint32
for i := uint(0); i < 35; i += 7 {
b, err := r.ReadByte()
if err != nil {
return 0, BufferOverrunError{Op: "Int32"}
}
ux |= uint32(b&0x7f) << i
if b&0x80 == 0 {
break
}
}
x := int32(ux >> 1)
if ux&1 != 0 {
x = ^x
}
return x, nil
}
// Int64 ...
func (networkLittleEndian) Int64(r *offsetReader) (int64, error) {
var ux uint64
for i := uint(0); i < 70; i += 7 {
b, err := r.ReadByte()
if err != nil {
return 0, BufferOverrunError{Op: "Int64"}
}
ux |= uint64(b&0x7f) << i
if b&0x80 == 0 {
break
}
}
x := int64(ux >> 1)
if ux&1 != 0 {
x = ^x
}
return x, nil
}
// String ...
func (e networkLittleEndian) String(r *offsetReader) (string, error) {
var length uint32
for i := uint(0); i < 35; i += 7 {
b, err := r.ReadByte()
if err != nil {
return "", BufferOverrunError{Op: "String"}
}
length |= uint32(b&0x7f) << i
if b&0x80 == 0 {
break
}
}
if length > math.MaxInt16 {
return "", InvalidStringError{Off: r.off, Err: errors.New("string length exceeds maximum length prefix")}
}
data, err := consumeN(int(length), r)
if err != nil {
return "", BufferOverrunError{Op: "String"}
}
return string(data), nil
}
type littleEndian struct{}
// WriteInt16 ...
func (littleEndian) WriteInt16(w *offsetWriter, x int16) error {
if _, err := w.Write([]byte{byte(x), byte(x >> 8)}); err != nil {
return FailedWriteError{Op: "WriteInt16", Off: w.off}
}
return nil
}
// WriteInt32 ...
func (littleEndian) WriteInt32(w *offsetWriter, x int32) error {
if _, err := w.Write([]byte{byte(x), byte(x >> 8), byte(x >> 16), byte(x >> 24)}); err != nil {
return FailedWriteError{Op: "WriteInt32", Off: w.off}
}
return nil
}
// WriteInt64 ...
func (littleEndian) WriteInt64(w *offsetWriter, x int64) error {
if _, err := w.Write([]byte{byte(x), byte(x >> 8), byte(x >> 16), byte(x >> 24),
byte(x >> 32), byte(x >> 40), byte(x >> 48), byte(x >> 56)}); err != nil {
return FailedWriteError{Op: "WriteInt64", Off: w.off}
}
return nil
}
// WriteFloat32 ...
func (littleEndian) WriteFloat32(w *offsetWriter, x float32) error {
bits := math.Float32bits(x)
if _, err := w.Write([]byte{byte(bits), byte(bits >> 8), byte(bits >> 16), byte(bits >> 24)}); err != nil {
return FailedWriteError{Op: "WriteFloat32", Off: w.off}
}
return nil
}
// WriteFloat64 ...
func (littleEndian) WriteFloat64(w *offsetWriter, x float64) error {
bits := math.Float64bits(x)
if _, err := w.Write([]byte{byte(bits), byte(bits >> 8), byte(bits >> 16), byte(bits >> 24),
byte(bits >> 32), byte(bits >> 40), byte(bits >> 48), byte(bits >> 56)}); err != nil {
return FailedWriteError{Op: "WriteFloat64", Off: w.off}
}
return nil
}
// WriteString ...
func (littleEndian) WriteString(w *offsetWriter, x string) error {
if len(x) > math.MaxInt16 {
return InvalidStringError{Off: w.off, String: x, Err: errors.New("string length exceeds maximum length prefix")}
}
length := int16(len(x))
if _, err := w.Write([]byte{byte(length), byte(length >> 8)}); err != nil {
return FailedWriteError{Op: "WriteString", Off: w.off}
}
// Use unsafe conversion from a string to a byte slice to prevent copying.
if _, err := w.Write(*(*[]byte)(unsafe.Pointer(&x))); err != nil {
return FailedWriteError{Op: "WriteString", Off: w.off}
}
return nil
}
// Int16 ...
func (littleEndian) Int16(r *offsetReader) (int16, error) {
b, err := consumeN(2, r)
if err != nil {
return 0, BufferOverrunError{Op: "Int16"}
}
return int16(uint16(b[0]) | uint16(b[1])<<8), nil
}
// Int32 ...
func (littleEndian) Int32(r *offsetReader) (int32, error) {
b, err := consumeN(4, r)
if err != nil {
return 0, BufferOverrunError{Op: "Int32"}
}
return int32(uint32(b[0]) | uint32(b[1])<<8 | uint32(b[2])<<16 | uint32(b[3])<<24), nil
}
// Int64 ...
func (littleEndian) Int64(r *offsetReader) (int64, error) {
b, err := consumeN(8, r)
if err != nil {
return 0, BufferOverrunError{Op: "Float64"}
}
return int64(uint64(b[0]) | uint64(b[1])<<8 | uint64(b[2])<<16 | uint64(b[3])<<24 |
uint64(b[4])<<32 | uint64(b[5])<<40 | uint64(b[6])<<48 | uint64(b[7])<<56), nil
}
// Float32 ...
func (littleEndian) Float32(r *offsetReader) (float32, error) {
b, err := consumeN(4, r)
if err != nil {
return 0, BufferOverrunError{Op: "Float32"}
}
return math.Float32frombits(uint32(b[0]) | uint32(b[1])<<8 | uint32(b[2])<<16 | uint32(b[3])<<24), nil
}
// Float64 ...
func (littleEndian) Float64(r *offsetReader) (float64, error) {
b, err := consumeN(8, r)
if err != nil {
return 0, BufferOverrunError{Op: "Float64"}
}
return math.Float64frombits(uint64(b[0]) | uint64(b[1])<<8 | uint64(b[2])<<16 | uint64(b[3])<<24 |
uint64(b[4])<<32 | uint64(b[5])<<40 | uint64(b[6])<<48 | uint64(b[7])<<56), nil
}
// String ...
func (littleEndian) String(r *offsetReader) (string, error) {
b, err := consumeN(2, r)
if err != nil {
return "", BufferOverrunError{Op: "String"}
}
stringLength := int(uint16(b[0]) | uint16(b[1])<<8)
data, err := consumeN(stringLength, r)
if err != nil {
return "", BufferOverrunError{Op: "String"}
}
return string(data), nil
}
type bigEndian struct{}
// WriteInt16 ...
func (bigEndian) WriteInt16(w *offsetWriter, x int16) error {
if _, err := w.Write([]byte{byte(x >> 8), byte(x)}); err != nil {
return FailedWriteError{Op: "WriteInt16", Off: w.off}
}
return nil
}
// WriteInt32 ...
func (bigEndian) WriteInt32(w *offsetWriter, x int32) error {
if _, err := w.Write([]byte{byte(x >> 24), byte(x >> 16), byte(x >> 8), byte(x)}); err != nil {
return FailedWriteError{Op: "WriteInt32", Off: w.off}
}
return nil
}
// WriteInt64 ...
func (bigEndian) WriteInt64(w *offsetWriter, x int64) error {
if _, err := w.Write([]byte{byte(x >> 56), byte(x >> 48), byte(x >> 40), byte(x >> 32),
byte(x >> 24), byte(x >> 16), byte(x >> 8), byte(x)}); err != nil {
return FailedWriteError{Op: "WriteInt64", Off: w.off}
}
return nil
}
// WriteFloat32 ...
func (bigEndian) WriteFloat32(w *offsetWriter, x float32) error {
bits := math.Float32bits(x)
if _, err := w.Write([]byte{byte(bits >> 24), byte(bits >> 16), byte(bits >> 8), byte(bits)}); err != nil {
return FailedWriteError{Op: "WriteFloat32", Off: w.off}
}
return nil
}
// WriteFloat64 ...
func (bigEndian) WriteFloat64(w *offsetWriter, x float64) error {
bits := math.Float64bits(x)
if _, err := w.Write([]byte{byte(bits >> 56), byte(bits >> 48), byte(bits >> 40), byte(bits >> 32),
byte(bits >> 24), byte(bits >> 16), byte(bits >> 8), byte(bits)}); err != nil {
return FailedWriteError{Op: "WriteFloat64", Off: w.off}
}
return nil
}
// WriteString ...
func (bigEndian) WriteString(w *offsetWriter, x string) error {
if len(x) > math.MaxInt16 {
return InvalidStringError{Off: w.off, String: x, Err: errors.New("string length exceeds maximum length prefix")}
}
length := int16(len(x))
if _, err := w.Write([]byte{byte(length >> 8), byte(length)}); err != nil {
return FailedWriteError{Op: "WriteInt16", Off: w.off}
}
// Use unsafe conversion from a string to a byte slice to prevent copying.
if _, err := w.Write(*(*[]byte)(unsafe.Pointer(&x))); err != nil {
return FailedWriteError{Op: "WriteString", Off: w.off}
}
return nil
}
// Int16 ...
func (bigEndian) Int16(r *offsetReader) (int16, error) {
b, err := consumeN(2, r)
if err != nil {
return 0, BufferOverrunError{Op: "Int16"}
}
return int16(uint16(b[0])<<8 | uint16(b[1])), nil
}
// Int32 ...
func (bigEndian) Int32(r *offsetReader) (int32, error) {
b, err := consumeN(4, r)
if err != nil {
return 0, BufferOverrunError{Op: "Int32"}
}
return int32(uint32(b[0])<<24 | uint32(b[1])<<16 | uint32(b[2])<<8 | uint32(b[3])), nil
}
// Int64 ...
func (bigEndian) Int64(r *offsetReader) (int64, error) {
b, err := consumeN(8, r)
if err != nil {
return 0, BufferOverrunError{Op: "Float64"}
}
return int64(uint64(b[0])<<56 | uint64(b[1])<<48 | uint64(b[2])<<40 | uint64(b[3])<<32 |
uint64(b[4])<<24 | uint64(b[5])<<16 | uint64(b[6])<<8 | uint64(b[7])), nil
}
// Float32 ...
func (bigEndian) Float32(r *offsetReader) (float32, error) {
b, err := consumeN(4, r)
if err != nil {
return 0, BufferOverrunError{Op: "Float32"}
}
return math.Float32frombits(uint32(b[0])<<24 | uint32(b[1])<<16 | uint32(b[2])<<8 | uint32(b[3])), nil
}
// Float64 ...
func (bigEndian) Float64(r *offsetReader) (float64, error) {
b, err := consumeN(8, r)
if err != nil {
return 0, BufferOverrunError{Op: "Float64"}
}
return math.Float64frombits(uint64(b[0])<<56 | uint64(b[1])<<48 | uint64(b[2])<<40 | uint64(b[3])<<32 |
uint64(b[4])<<24 | uint64(b[5])<<16 | uint64(b[6])<<8 | uint64(b[7])), nil
}
// String ...
func (bigEndian) String(r *offsetReader) (string, error) {
b, err := consumeN(2, r)
if err != nil {
return "", BufferOverrunError{Op: "String"}
}
stringLength := int(uint16(b[0])<<8 | uint16(b[1]))
data, err := consumeN(stringLength, r)
if err != nil {
return "", BufferOverrunError{Op: "String"}
}
return string(data), nil
}
// consumeN consumes n bytes from the offset reader and returns them. It returns an error if the reader does
// not have that many bytes available.
func consumeN(n int, r *offsetReader) ([]byte, error) {
if n < 0 {
return nil, InvalidArraySizeError{Off: r.off, Op: "Consume", NBTLength: n}
}
data := r.Next(n)
if len(data) != n {
return nil, BufferOverrunError{Op: "Consume"}
}
return data, nil
}