Source file src/encoding/binary/binary.go

     1  // Copyright 2009 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // Package binary implements simple translation between numbers and byte
     6  // sequences and encoding and decoding of varints.
     7  //
     8  // Numbers are translated by reading and writing fixed-size values.
     9  // A fixed-size value is either a fixed-size arithmetic
    10  // type (bool, int8, uint8, int16, float32, complex64, ...)
    11  // or an array or struct containing only fixed-size values.
    12  //
    13  // The varint functions encode and decode single integer values using
    14  // a variable-length encoding; smaller values require fewer bytes.
    15  // For a specification, see
    16  // https://developers.google.com/protocol-buffers/docs/encoding.
    17  //
    18  // This package favors simplicity over efficiency. Clients that require
    19  // high-performance serialization, especially for large data structures,
    20  // should look at more advanced solutions such as the [encoding/gob]
    21  // package or [google.golang.org/protobuf] for protocol buffers.
    22  package binary
    23  
    24  import (
    25  	"errors"
    26  	"io"
    27  	"math"
    28  	"reflect"
    29  	"slices"
    30  	"sync"
    31  )
    32  
    33  var errBufferTooSmall = errors.New("buffer too small")
    34  
    35  // A ByteOrder specifies how to convert byte slices into
    36  // 16-, 32-, or 64-bit unsigned integers.
    37  //
    38  // It is implemented by [LittleEndian], [BigEndian], and [NativeEndian].
    39  type ByteOrder interface {
    40  	Uint16([]byte) uint16
    41  	Uint32([]byte) uint32
    42  	Uint64([]byte) uint64
    43  	PutUint16([]byte, uint16)
    44  	PutUint32([]byte, uint32)
    45  	PutUint64([]byte, uint64)
    46  	String() string
    47  }
    48  
    49  // AppendByteOrder specifies how to append 16-, 32-, or 64-bit unsigned integers
    50  // into a byte slice.
    51  //
    52  // It is implemented by [LittleEndian], [BigEndian], and [NativeEndian].
    53  type AppendByteOrder interface {
    54  	AppendUint16([]byte, uint16) []byte
    55  	AppendUint32([]byte, uint32) []byte
    56  	AppendUint64([]byte, uint64) []byte
    57  	String() string
    58  }
    59  
    60  // LittleEndian is the little-endian implementation of [ByteOrder] and [AppendByteOrder].
    61  var LittleEndian littleEndian
    62  
    63  // BigEndian is the big-endian implementation of [ByteOrder] and [AppendByteOrder].
    64  var BigEndian bigEndian
    65  
    66  type littleEndian struct{}
    67  
    68  // Uint16 returns the uint16 representation of b[0:2].
    69  func (littleEndian) Uint16(b []byte) uint16 {
    70  	_ = b[1] // bounds check hint to compiler; see golang.org/issue/14808
    71  	return uint16(b[0]) | uint16(b[1])<<8
    72  }
    73  
    74  // PutUint16 stores v into b[0:2].
    75  func (littleEndian) PutUint16(b []byte, v uint16) {
    76  	_ = b[1] // early bounds check to guarantee safety of writes below
    77  	b[0] = byte(v)
    78  	b[1] = byte(v >> 8)
    79  }
    80  
    81  // AppendUint16 appends the bytes of v to b and returns the appended slice.
    82  func (littleEndian) AppendUint16(b []byte, v uint16) []byte {
    83  	return append(b,
    84  		byte(v),
    85  		byte(v>>8),
    86  	)
    87  }
    88  
    89  // Uint32 returns the uint32 representation of b[0:4].
    90  func (littleEndian) Uint32(b []byte) uint32 {
    91  	_ = b[3] // bounds check hint to compiler; see golang.org/issue/14808
    92  	return uint32(b[0]) | uint32(b[1])<<8 | uint32(b[2])<<16 | uint32(b[3])<<24
    93  }
    94  
    95  // PutUint32 stores v into b[0:4].
    96  func (littleEndian) PutUint32(b []byte, v uint32) {
    97  	_ = b[3] // early bounds check to guarantee safety of writes below
    98  	b[0] = byte(v)
    99  	b[1] = byte(v >> 8)
   100  	b[2] = byte(v >> 16)
   101  	b[3] = byte(v >> 24)
   102  }
   103  
   104  // AppendUint32 appends the bytes of v to b and returns the appended slice.
   105  func (littleEndian) AppendUint32(b []byte, v uint32) []byte {
   106  	return append(b,
   107  		byte(v),
   108  		byte(v>>8),
   109  		byte(v>>16),
   110  		byte(v>>24),
   111  	)
   112  }
   113  
   114  // Uint64 returns the uint64 representation of b[0:8].
   115  func (littleEndian) Uint64(b []byte) uint64 {
   116  	_ = b[7] // bounds check hint to compiler; see golang.org/issue/14808
   117  	return uint64(b[0]) | uint64(b[1])<<8 | uint64(b[2])<<16 | uint64(b[3])<<24 |
   118  		uint64(b[4])<<32 | uint64(b[5])<<40 | uint64(b[6])<<48 | uint64(b[7])<<56
   119  }
   120  
   121  // PutUint64 stores v into b[0:8].
   122  func (littleEndian) PutUint64(b []byte, v uint64) {
   123  	_ = b[7] // early bounds check to guarantee safety of writes below
   124  	b[0] = byte(v)
   125  	b[1] = byte(v >> 8)
   126  	b[2] = byte(v >> 16)
   127  	b[3] = byte(v >> 24)
   128  	b[4] = byte(v >> 32)
   129  	b[5] = byte(v >> 40)
   130  	b[6] = byte(v >> 48)
   131  	b[7] = byte(v >> 56)
   132  }
   133  
   134  // AppendUint64 appends the bytes of v to b and returns the appended slice.
   135  func (littleEndian) AppendUint64(b []byte, v uint64) []byte {
   136  	return append(b,
   137  		byte(v),
   138  		byte(v>>8),
   139  		byte(v>>16),
   140  		byte(v>>24),
   141  		byte(v>>32),
   142  		byte(v>>40),
   143  		byte(v>>48),
   144  		byte(v>>56),
   145  	)
   146  }
   147  
   148  func (littleEndian) String() string { return "LittleEndian" }
   149  
   150  func (littleEndian) GoString() string { return "binary.LittleEndian" }
   151  
   152  type bigEndian struct{}
   153  
   154  // Uint16 returns the uint16 representation of b[0:2].
   155  func (bigEndian) Uint16(b []byte) uint16 {
   156  	_ = b[1] // bounds check hint to compiler; see golang.org/issue/14808
   157  	return uint16(b[1]) | uint16(b[0])<<8
   158  }
   159  
   160  // PutUint16 stores v into b[0:2].
   161  func (bigEndian) PutUint16(b []byte, v uint16) {
   162  	_ = b[1] // early bounds check to guarantee safety of writes below
   163  	b[0] = byte(v >> 8)
   164  	b[1] = byte(v)
   165  }
   166  
   167  // AppendUint16 appends the bytes of v to b and returns the appended slice.
   168  func (bigEndian) AppendUint16(b []byte, v uint16) []byte {
   169  	return append(b,
   170  		byte(v>>8),
   171  		byte(v),
   172  	)
   173  }
   174  
   175  // Uint32 returns the uint32 representation of b[0:4].
   176  func (bigEndian) Uint32(b []byte) uint32 {
   177  	_ = b[3] // bounds check hint to compiler; see golang.org/issue/14808
   178  	return uint32(b[3]) | uint32(b[2])<<8 | uint32(b[1])<<16 | uint32(b[0])<<24
   179  }
   180  
   181  // PutUint32 stores v into b[0:4].
   182  func (bigEndian) PutUint32(b []byte, v uint32) {
   183  	_ = b[3] // early bounds check to guarantee safety of writes below
   184  	b[0] = byte(v >> 24)
   185  	b[1] = byte(v >> 16)
   186  	b[2] = byte(v >> 8)
   187  	b[3] = byte(v)
   188  }
   189  
   190  // AppendUint32 appends the bytes of v to b and returns the appended slice.
   191  func (bigEndian) AppendUint32(b []byte, v uint32) []byte {
   192  	return append(b,
   193  		byte(v>>24),
   194  		byte(v>>16),
   195  		byte(v>>8),
   196  		byte(v),
   197  	)
   198  }
   199  
   200  // Uint64 returns the uint64 representation of b[0:8].
   201  func (bigEndian) Uint64(b []byte) uint64 {
   202  	_ = b[7] // bounds check hint to compiler; see golang.org/issue/14808
   203  	return uint64(b[7]) | uint64(b[6])<<8 | uint64(b[5])<<16 | uint64(b[4])<<24 |
   204  		uint64(b[3])<<32 | uint64(b[2])<<40 | uint64(b[1])<<48 | uint64(b[0])<<56
   205  }
   206  
   207  // PutUint64 stores v into b[0:8].
   208  func (bigEndian) PutUint64(b []byte, v uint64) {
   209  	_ = b[7] // early bounds check to guarantee safety of writes below
   210  	b[0] = byte(v >> 56)
   211  	b[1] = byte(v >> 48)
   212  	b[2] = byte(v >> 40)
   213  	b[3] = byte(v >> 32)
   214  	b[4] = byte(v >> 24)
   215  	b[5] = byte(v >> 16)
   216  	b[6] = byte(v >> 8)
   217  	b[7] = byte(v)
   218  }
   219  
   220  // AppendUint64 appends the bytes of v to b and returns the appended slice.
   221  func (bigEndian) AppendUint64(b []byte, v uint64) []byte {
   222  	return append(b,
   223  		byte(v>>56),
   224  		byte(v>>48),
   225  		byte(v>>40),
   226  		byte(v>>32),
   227  		byte(v>>24),
   228  		byte(v>>16),
   229  		byte(v>>8),
   230  		byte(v),
   231  	)
   232  }
   233  
   234  func (bigEndian) String() string { return "BigEndian" }
   235  
   236  func (bigEndian) GoString() string { return "binary.BigEndian" }
   237  
   238  func (nativeEndian) String() string { return "NativeEndian" }
   239  
   240  func (nativeEndian) GoString() string { return "binary.NativeEndian" }
   241  
   242  // Read reads structured binary data from r into data.
   243  // Data must be a pointer to a fixed-size value or a slice
   244  // of fixed-size values.
   245  // Bytes read from r are decoded using the specified byte order
   246  // and written to successive fields of the data.
   247  // When decoding boolean values, a zero byte is decoded as false, and
   248  // any other non-zero byte is decoded as true.
   249  // When reading into structs, the field data for fields with
   250  // blank (_) field names is skipped; i.e., blank field names
   251  // may be used for padding.
   252  // When reading into a struct, all non-blank fields must be exported
   253  // or Read may panic.
   254  //
   255  // The error is [io.EOF] only if no bytes were read.
   256  // If an [io.EOF] happens after reading some but not all the bytes,
   257  // Read returns [io.ErrUnexpectedEOF].
   258  func Read(r io.Reader, order ByteOrder, data any) error {
   259  	// Fast path for basic types and slices.
   260  	if n, _ := intDataSize(data); n != 0 {
   261  		bs := make([]byte, n)
   262  		if _, err := io.ReadFull(r, bs); err != nil {
   263  			return err
   264  		}
   265  
   266  		if decodeFast(bs, order, data) {
   267  			return nil
   268  		}
   269  	}
   270  
   271  	// Fallback to reflect-based decoding.
   272  	v := reflect.ValueOf(data)
   273  	size := -1
   274  	switch v.Kind() {
   275  	case reflect.Pointer:
   276  		v = v.Elem()
   277  		size = dataSize(v)
   278  	case reflect.Slice:
   279  		size = dataSize(v)
   280  	}
   281  	if size < 0 {
   282  		return errors.New("binary.Read: invalid type " + reflect.TypeOf(data).String())
   283  	}
   284  
   285  	d := &decoder{order: order, buf: make([]byte, size)}
   286  	if _, err := io.ReadFull(r, d.buf); err != nil {
   287  		return err
   288  	}
   289  	d.value(v)
   290  	return nil
   291  }
   292  
   293  // Decode decodes binary data from buf into data according to
   294  // the given byte order.
   295  // It returns an error if buf is too small, otherwise the number of
   296  // bytes consumed from buf.
   297  func Decode(buf []byte, order ByteOrder, data any) (int, error) {
   298  	if n, _ := intDataSize(data); n != 0 {
   299  		if len(buf) < n {
   300  			return 0, errBufferTooSmall
   301  		}
   302  
   303  		if decodeFast(buf, order, data) {
   304  			return n, nil
   305  		}
   306  	}
   307  
   308  	// Fallback to reflect-based decoding.
   309  	v := reflect.ValueOf(data)
   310  	size := -1
   311  	switch v.Kind() {
   312  	case reflect.Pointer:
   313  		v = v.Elem()
   314  		size = dataSize(v)
   315  	case reflect.Slice:
   316  		size = dataSize(v)
   317  	}
   318  	if size < 0 {
   319  		return 0, errors.New("binary.Decode: invalid type " + reflect.TypeOf(data).String())
   320  	}
   321  
   322  	if len(buf) < size {
   323  		return 0, errBufferTooSmall
   324  	}
   325  	d := &decoder{order: order, buf: buf[:size]}
   326  	d.value(v)
   327  	return size, nil
   328  }
   329  
   330  func decodeFast(bs []byte, order ByteOrder, data any) bool {
   331  	switch data := data.(type) {
   332  	case *bool:
   333  		*data = bs[0] != 0
   334  	case *int8:
   335  		*data = int8(bs[0])
   336  	case *uint8:
   337  		*data = bs[0]
   338  	case *int16:
   339  		*data = int16(order.Uint16(bs))
   340  	case *uint16:
   341  		*data = order.Uint16(bs)
   342  	case *int32:
   343  		*data = int32(order.Uint32(bs))
   344  	case *uint32:
   345  		*data = order.Uint32(bs)
   346  	case *int64:
   347  		*data = int64(order.Uint64(bs))
   348  	case *uint64:
   349  		*data = order.Uint64(bs)
   350  	case *float32:
   351  		*data = math.Float32frombits(order.Uint32(bs))
   352  	case *float64:
   353  		*data = math.Float64frombits(order.Uint64(bs))
   354  	case []bool:
   355  		for i, x := range bs { // Easier to loop over the input for 8-bit values.
   356  			data[i] = x != 0
   357  		}
   358  	case []int8:
   359  		for i, x := range bs {
   360  			data[i] = int8(x)
   361  		}
   362  	case []uint8:
   363  		copy(data, bs)
   364  	case []int16:
   365  		for i := range data {
   366  			data[i] = int16(order.Uint16(bs[2*i:]))
   367  		}
   368  	case []uint16:
   369  		for i := range data {
   370  			data[i] = order.Uint16(bs[2*i:])
   371  		}
   372  	case []int32:
   373  		for i := range data {
   374  			data[i] = int32(order.Uint32(bs[4*i:]))
   375  		}
   376  	case []uint32:
   377  		for i := range data {
   378  			data[i] = order.Uint32(bs[4*i:])
   379  		}
   380  	case []int64:
   381  		for i := range data {
   382  			data[i] = int64(order.Uint64(bs[8*i:]))
   383  		}
   384  	case []uint64:
   385  		for i := range data {
   386  			data[i] = order.Uint64(bs[8*i:])
   387  		}
   388  	case []float32:
   389  		for i := range data {
   390  			data[i] = math.Float32frombits(order.Uint32(bs[4*i:]))
   391  		}
   392  	case []float64:
   393  		for i := range data {
   394  			data[i] = math.Float64frombits(order.Uint64(bs[8*i:]))
   395  		}
   396  	default:
   397  		return false
   398  	}
   399  	return true
   400  }
   401  
   402  // Write writes the binary representation of data into w.
   403  // Data must be a fixed-size value or a slice of fixed-size
   404  // values, or a pointer to such data.
   405  // Boolean values encode as one byte: 1 for true, and 0 for false.
   406  // Bytes written to w are encoded using the specified byte order
   407  // and read from successive fields of the data.
   408  // When writing structs, zero values are written for fields
   409  // with blank (_) field names.
   410  func Write(w io.Writer, order ByteOrder, data any) error {
   411  	// Fast path for basic types and slices.
   412  	if n, bs := intDataSize(data); n != 0 {
   413  		if bs == nil {
   414  			bs = make([]byte, n)
   415  			encodeFast(bs, order, data)
   416  		}
   417  
   418  		_, err := w.Write(bs)
   419  		return err
   420  	}
   421  
   422  	// Fallback to reflect-based encoding.
   423  	v := reflect.Indirect(reflect.ValueOf(data))
   424  	size := dataSize(v)
   425  	if size < 0 {
   426  		return errors.New("binary.Write: some values are not fixed-sized in type " + reflect.TypeOf(data).String())
   427  	}
   428  
   429  	buf := make([]byte, size)
   430  	e := &encoder{order: order, buf: buf}
   431  	e.value(v)
   432  	_, err := w.Write(buf)
   433  	return err
   434  }
   435  
   436  // Encode encodes the binary representation of data into buf according to
   437  // the given byte order.
   438  // It returns an error if buf is too small, otherwise the number of
   439  // bytes written into buf.
   440  func Encode(buf []byte, order ByteOrder, data any) (int, error) {
   441  	// Fast path for basic types and slices.
   442  	if n, _ := intDataSize(data); n != 0 {
   443  		if len(buf) < n {
   444  			return 0, errBufferTooSmall
   445  		}
   446  
   447  		encodeFast(buf, order, data)
   448  		return n, nil
   449  	}
   450  
   451  	// Fallback to reflect-based encoding.
   452  	v := reflect.Indirect(reflect.ValueOf(data))
   453  	size := dataSize(v)
   454  	if size < 0 {
   455  		return 0, errors.New("binary.Encode: some values are not fixed-sized in type " + reflect.TypeOf(data).String())
   456  	}
   457  
   458  	if len(buf) < size {
   459  		return 0, errBufferTooSmall
   460  	}
   461  	e := &encoder{order: order, buf: buf}
   462  	e.value(v)
   463  	return size, nil
   464  }
   465  
   466  // Append appends the binary representation of data to buf.
   467  // buf may be nil, in which case a new buffer will be allocated.
   468  // See [Write] on which data are acceptable.
   469  // It returns the (possibly extended) buffer containing data or an error.
   470  func Append(buf []byte, order ByteOrder, data any) ([]byte, error) {
   471  	// Fast path for basic types and slices.
   472  	if n, _ := intDataSize(data); n != 0 {
   473  		buf, pos := ensure(buf, n)
   474  		encodeFast(pos, order, data)
   475  		return buf, nil
   476  	}
   477  
   478  	// Fallback to reflect-based encoding.
   479  	v := reflect.Indirect(reflect.ValueOf(data))
   480  	size := dataSize(v)
   481  	if size < 0 {
   482  		return nil, errors.New("binary.Append: some values are not fixed-sized in type " + reflect.TypeOf(data).String())
   483  	}
   484  
   485  	buf, pos := ensure(buf, size)
   486  	e := &encoder{order: order, buf: pos}
   487  	e.value(v)
   488  	return buf, nil
   489  }
   490  
   491  func encodeFast(bs []byte, order ByteOrder, data any) {
   492  	switch v := data.(type) {
   493  	case *bool:
   494  		if *v {
   495  			bs[0] = 1
   496  		} else {
   497  			bs[0] = 0
   498  		}
   499  	case bool:
   500  		if v {
   501  			bs[0] = 1
   502  		} else {
   503  			bs[0] = 0
   504  		}
   505  	case []bool:
   506  		for i, x := range v {
   507  			if x {
   508  				bs[i] = 1
   509  			} else {
   510  				bs[i] = 0
   511  			}
   512  		}
   513  	case *int8:
   514  		bs[0] = byte(*v)
   515  	case int8:
   516  		bs[0] = byte(v)
   517  	case []int8:
   518  		for i, x := range v {
   519  			bs[i] = byte(x)
   520  		}
   521  	case *uint8:
   522  		bs[0] = *v
   523  	case uint8:
   524  		bs[0] = v
   525  	case []uint8:
   526  		copy(bs, v)
   527  	case *int16:
   528  		order.PutUint16(bs, uint16(*v))
   529  	case int16:
   530  		order.PutUint16(bs, uint16(v))
   531  	case []int16:
   532  		for i, x := range v {
   533  			order.PutUint16(bs[2*i:], uint16(x))
   534  		}
   535  	case *uint16:
   536  		order.PutUint16(bs, *v)
   537  	case uint16:
   538  		order.PutUint16(bs, v)
   539  	case []uint16:
   540  		for i, x := range v {
   541  			order.PutUint16(bs[2*i:], x)
   542  		}
   543  	case *int32:
   544  		order.PutUint32(bs, uint32(*v))
   545  	case int32:
   546  		order.PutUint32(bs, uint32(v))
   547  	case []int32:
   548  		for i, x := range v {
   549  			order.PutUint32(bs[4*i:], uint32(x))
   550  		}
   551  	case *uint32:
   552  		order.PutUint32(bs, *v)
   553  	case uint32:
   554  		order.PutUint32(bs, v)
   555  	case []uint32:
   556  		for i, x := range v {
   557  			order.PutUint32(bs[4*i:], x)
   558  		}
   559  	case *int64:
   560  		order.PutUint64(bs, uint64(*v))
   561  	case int64:
   562  		order.PutUint64(bs, uint64(v))
   563  	case []int64:
   564  		for i, x := range v {
   565  			order.PutUint64(bs[8*i:], uint64(x))
   566  		}
   567  	case *uint64:
   568  		order.PutUint64(bs, *v)
   569  	case uint64:
   570  		order.PutUint64(bs, v)
   571  	case []uint64:
   572  		for i, x := range v {
   573  			order.PutUint64(bs[8*i:], x)
   574  		}
   575  	case *float32:
   576  		order.PutUint32(bs, math.Float32bits(*v))
   577  	case float32:
   578  		order.PutUint32(bs, math.Float32bits(v))
   579  	case []float32:
   580  		for i, x := range v {
   581  			order.PutUint32(bs[4*i:], math.Float32bits(x))
   582  		}
   583  	case *float64:
   584  		order.PutUint64(bs, math.Float64bits(*v))
   585  	case float64:
   586  		order.PutUint64(bs, math.Float64bits(v))
   587  	case []float64:
   588  		for i, x := range v {
   589  			order.PutUint64(bs[8*i:], math.Float64bits(x))
   590  		}
   591  	}
   592  }
   593  
   594  // Size returns how many bytes [Write] would generate to encode the value v, which
   595  // must be a fixed-size value or a slice of fixed-size values, or a pointer to such data.
   596  // If v is neither of these, Size returns -1.
   597  func Size(v any) int {
   598  	switch data := v.(type) {
   599  	case bool, int8, uint8:
   600  		return 1
   601  	case *bool:
   602  		if data == nil {
   603  			return -1
   604  		}
   605  		return 1
   606  	case *int8:
   607  		if data == nil {
   608  			return -1
   609  		}
   610  		return 1
   611  	case *uint8:
   612  		if data == nil {
   613  			return -1
   614  		}
   615  		return 1
   616  	case []bool:
   617  		return len(data)
   618  	case []int8:
   619  		return len(data)
   620  	case []uint8:
   621  		return len(data)
   622  	case int16, uint16:
   623  		return 2
   624  	case *int16:
   625  		if data == nil {
   626  			return -1
   627  		}
   628  		return 2
   629  	case *uint16:
   630  		if data == nil {
   631  			return -1
   632  		}
   633  		return 2
   634  	case []int16:
   635  		return 2 * len(data)
   636  	case []uint16:
   637  		return 2 * len(data)
   638  	case int32, uint32:
   639  		return 4
   640  	case *int32:
   641  		if data == nil {
   642  			return -1
   643  		}
   644  		return 4
   645  	case *uint32:
   646  		if data == nil {
   647  			return -1
   648  		}
   649  		return 4
   650  	case []int32:
   651  		return 4 * len(data)
   652  	case []uint32:
   653  		return 4 * len(data)
   654  	case int64, uint64:
   655  		return 8
   656  	case *int64:
   657  		if data == nil {
   658  			return -1
   659  		}
   660  		return 8
   661  	case *uint64:
   662  		if data == nil {
   663  			return -1
   664  		}
   665  		return 8
   666  	case []int64:
   667  		return 8 * len(data)
   668  	case []uint64:
   669  		return 8 * len(data)
   670  	case float32:
   671  		return 4
   672  	case *float32:
   673  		if data == nil {
   674  			return -1
   675  		}
   676  		return 4
   677  	case float64:
   678  		return 8
   679  	case *float64:
   680  		if data == nil {
   681  			return -1
   682  		}
   683  		return 8
   684  	case []float32:
   685  		return 4 * len(data)
   686  	case []float64:
   687  		return 8 * len(data)
   688  	}
   689  	return dataSize(reflect.Indirect(reflect.ValueOf(v)))
   690  }
   691  
   692  var structSize sync.Map // map[reflect.Type]int
   693  
   694  // dataSize returns the number of bytes the actual data represented by v occupies in memory.
   695  // For compound structures, it sums the sizes of the elements. Thus, for instance, for a slice
   696  // it returns the length of the slice times the element size and does not count the memory
   697  // occupied by the header. If the type of v is not acceptable, dataSize returns -1.
   698  func dataSize(v reflect.Value) int {
   699  	switch v.Kind() {
   700  	case reflect.Slice, reflect.Array:
   701  		t := v.Type().Elem()
   702  		if size, ok := structSize.Load(t); ok {
   703  			return size.(int) * v.Len()
   704  		}
   705  
   706  		size := sizeof(t)
   707  		if size >= 0 {
   708  			if t.Kind() == reflect.Struct {
   709  				structSize.Store(t, size)
   710  			}
   711  			return size * v.Len()
   712  		}
   713  
   714  	case reflect.Struct:
   715  		t := v.Type()
   716  		if size, ok := structSize.Load(t); ok {
   717  			return size.(int)
   718  		}
   719  		size := sizeof(t)
   720  		structSize.Store(t, size)
   721  		return size
   722  
   723  	default:
   724  		if v.IsValid() {
   725  			return sizeof(v.Type())
   726  		}
   727  	}
   728  
   729  	return -1
   730  }
   731  
   732  // sizeof returns the size >= 0 of variables for the given type or -1 if the type is not acceptable.
   733  func sizeof(t reflect.Type) int {
   734  	switch t.Kind() {
   735  	case reflect.Array:
   736  		if s := sizeof(t.Elem()); s >= 0 {
   737  			return s * t.Len()
   738  		}
   739  
   740  	case reflect.Struct:
   741  		sum := 0
   742  		for i, n := 0, t.NumField(); i < n; i++ {
   743  			s := sizeof(t.Field(i).Type)
   744  			if s < 0 {
   745  				return -1
   746  			}
   747  			sum += s
   748  		}
   749  		return sum
   750  
   751  	case reflect.Bool,
   752  		reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64,
   753  		reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
   754  		reflect.Float32, reflect.Float64, reflect.Complex64, reflect.Complex128:
   755  		return int(t.Size())
   756  	}
   757  
   758  	return -1
   759  }
   760  
   761  type coder struct {
   762  	order  ByteOrder
   763  	buf    []byte
   764  	offset int
   765  }
   766  
   767  type decoder coder
   768  type encoder coder
   769  
   770  func (d *decoder) bool() bool {
   771  	x := d.buf[d.offset]
   772  	d.offset++
   773  	return x != 0
   774  }
   775  
   776  func (e *encoder) bool(x bool) {
   777  	if x {
   778  		e.buf[e.offset] = 1
   779  	} else {
   780  		e.buf[e.offset] = 0
   781  	}
   782  	e.offset++
   783  }
   784  
   785  func (d *decoder) uint8() uint8 {
   786  	x := d.buf[d.offset]
   787  	d.offset++
   788  	return x
   789  }
   790  
   791  func (e *encoder) uint8(x uint8) {
   792  	e.buf[e.offset] = x
   793  	e.offset++
   794  }
   795  
   796  func (d *decoder) uint16() uint16 {
   797  	x := d.order.Uint16(d.buf[d.offset : d.offset+2])
   798  	d.offset += 2
   799  	return x
   800  }
   801  
   802  func (e *encoder) uint16(x uint16) {
   803  	e.order.PutUint16(e.buf[e.offset:e.offset+2], x)
   804  	e.offset += 2
   805  }
   806  
   807  func (d *decoder) uint32() uint32 {
   808  	x := d.order.Uint32(d.buf[d.offset : d.offset+4])
   809  	d.offset += 4
   810  	return x
   811  }
   812  
   813  func (e *encoder) uint32(x uint32) {
   814  	e.order.PutUint32(e.buf[e.offset:e.offset+4], x)
   815  	e.offset += 4
   816  }
   817  
   818  func (d *decoder) uint64() uint64 {
   819  	x := d.order.Uint64(d.buf[d.offset : d.offset+8])
   820  	d.offset += 8
   821  	return x
   822  }
   823  
   824  func (e *encoder) uint64(x uint64) {
   825  	e.order.PutUint64(e.buf[e.offset:e.offset+8], x)
   826  	e.offset += 8
   827  }
   828  
   829  func (d *decoder) int8() int8 { return int8(d.uint8()) }
   830  
   831  func (e *encoder) int8(x int8) { e.uint8(uint8(x)) }
   832  
   833  func (d *decoder) int16() int16 { return int16(d.uint16()) }
   834  
   835  func (e *encoder) int16(x int16) { e.uint16(uint16(x)) }
   836  
   837  func (d *decoder) int32() int32 { return int32(d.uint32()) }
   838  
   839  func (e *encoder) int32(x int32) { e.uint32(uint32(x)) }
   840  
   841  func (d *decoder) int64() int64 { return int64(d.uint64()) }
   842  
   843  func (e *encoder) int64(x int64) { e.uint64(uint64(x)) }
   844  
   845  func (d *decoder) value(v reflect.Value) {
   846  	switch v.Kind() {
   847  	case reflect.Array:
   848  		l := v.Len()
   849  		for i := 0; i < l; i++ {
   850  			d.value(v.Index(i))
   851  		}
   852  
   853  	case reflect.Struct:
   854  		t := v.Type()
   855  		l := v.NumField()
   856  		for i := 0; i < l; i++ {
   857  			// Note: Calling v.CanSet() below is an optimization.
   858  			// It would be sufficient to check the field name,
   859  			// but creating the StructField info for each field is
   860  			// costly (run "go test -bench=ReadStruct" and compare
   861  			// results when making changes to this code).
   862  			if v := v.Field(i); v.CanSet() || t.Field(i).Name != "_" {
   863  				d.value(v)
   864  			} else {
   865  				d.skip(v)
   866  			}
   867  		}
   868  
   869  	case reflect.Slice:
   870  		l := v.Len()
   871  		for i := 0; i < l; i++ {
   872  			d.value(v.Index(i))
   873  		}
   874  
   875  	case reflect.Bool:
   876  		v.SetBool(d.bool())
   877  
   878  	case reflect.Int8:
   879  		v.SetInt(int64(d.int8()))
   880  	case reflect.Int16:
   881  		v.SetInt(int64(d.int16()))
   882  	case reflect.Int32:
   883  		v.SetInt(int64(d.int32()))
   884  	case reflect.Int64:
   885  		v.SetInt(d.int64())
   886  
   887  	case reflect.Uint8:
   888  		v.SetUint(uint64(d.uint8()))
   889  	case reflect.Uint16:
   890  		v.SetUint(uint64(d.uint16()))
   891  	case reflect.Uint32:
   892  		v.SetUint(uint64(d.uint32()))
   893  	case reflect.Uint64:
   894  		v.SetUint(d.uint64())
   895  
   896  	case reflect.Float32:
   897  		v.SetFloat(float64(math.Float32frombits(d.uint32())))
   898  	case reflect.Float64:
   899  		v.SetFloat(math.Float64frombits(d.uint64()))
   900  
   901  	case reflect.Complex64:
   902  		v.SetComplex(complex(
   903  			float64(math.Float32frombits(d.uint32())),
   904  			float64(math.Float32frombits(d.uint32())),
   905  		))
   906  	case reflect.Complex128:
   907  		v.SetComplex(complex(
   908  			math.Float64frombits(d.uint64()),
   909  			math.Float64frombits(d.uint64()),
   910  		))
   911  	}
   912  }
   913  
   914  func (e *encoder) value(v reflect.Value) {
   915  	switch v.Kind() {
   916  	case reflect.Array:
   917  		l := v.Len()
   918  		for i := 0; i < l; i++ {
   919  			e.value(v.Index(i))
   920  		}
   921  
   922  	case reflect.Struct:
   923  		t := v.Type()
   924  		l := v.NumField()
   925  		for i := 0; i < l; i++ {
   926  			// see comment for corresponding code in decoder.value()
   927  			if v := v.Field(i); v.CanSet() || t.Field(i).Name != "_" {
   928  				e.value(v)
   929  			} else {
   930  				e.skip(v)
   931  			}
   932  		}
   933  
   934  	case reflect.Slice:
   935  		l := v.Len()
   936  		for i := 0; i < l; i++ {
   937  			e.value(v.Index(i))
   938  		}
   939  
   940  	case reflect.Bool:
   941  		e.bool(v.Bool())
   942  
   943  	case reflect.Int8:
   944  		e.int8(int8(v.Int()))
   945  	case reflect.Int16:
   946  		e.int16(int16(v.Int()))
   947  	case reflect.Int32:
   948  		e.int32(int32(v.Int()))
   949  	case reflect.Int64:
   950  		e.int64(v.Int())
   951  
   952  	case reflect.Uint8:
   953  		e.uint8(uint8(v.Uint()))
   954  	case reflect.Uint16:
   955  		e.uint16(uint16(v.Uint()))
   956  	case reflect.Uint32:
   957  		e.uint32(uint32(v.Uint()))
   958  	case reflect.Uint64:
   959  		e.uint64(v.Uint())
   960  
   961  	case reflect.Float32:
   962  		e.uint32(math.Float32bits(float32(v.Float())))
   963  	case reflect.Float64:
   964  		e.uint64(math.Float64bits(v.Float()))
   965  
   966  	case reflect.Complex64:
   967  		x := v.Complex()
   968  		e.uint32(math.Float32bits(float32(real(x))))
   969  		e.uint32(math.Float32bits(float32(imag(x))))
   970  	case reflect.Complex128:
   971  		x := v.Complex()
   972  		e.uint64(math.Float64bits(real(x)))
   973  		e.uint64(math.Float64bits(imag(x)))
   974  	}
   975  }
   976  
   977  func (d *decoder) skip(v reflect.Value) {
   978  	d.offset += dataSize(v)
   979  }
   980  
   981  func (e *encoder) skip(v reflect.Value) {
   982  	n := dataSize(v)
   983  	clear(e.buf[e.offset : e.offset+n])
   984  	e.offset += n
   985  }
   986  
   987  // intDataSize returns the size of the data required to represent the data when encoded,
   988  // and optionally a byte slice containing the encoded data if no conversion is necessary.
   989  // It returns zero, nil if the type cannot be implemented by the fast path in Read or Write.
   990  func intDataSize(data any) (int, []byte) {
   991  	switch data := data.(type) {
   992  	case bool, int8, uint8, *bool, *int8, *uint8:
   993  		return 1, nil
   994  	case []bool:
   995  		return len(data), nil
   996  	case []int8:
   997  		return len(data), nil
   998  	case []uint8:
   999  		return len(data), data
  1000  	case int16, uint16, *int16, *uint16:
  1001  		return 2, nil
  1002  	case []int16:
  1003  		return 2 * len(data), nil
  1004  	case []uint16:
  1005  		return 2 * len(data), nil
  1006  	case int32, uint32, *int32, *uint32:
  1007  		return 4, nil
  1008  	case []int32:
  1009  		return 4 * len(data), nil
  1010  	case []uint32:
  1011  		return 4 * len(data), nil
  1012  	case int64, uint64, *int64, *uint64:
  1013  		return 8, nil
  1014  	case []int64:
  1015  		return 8 * len(data), nil
  1016  	case []uint64:
  1017  		return 8 * len(data), nil
  1018  	case float32, *float32:
  1019  		return 4, nil
  1020  	case float64, *float64:
  1021  		return 8, nil
  1022  	case []float32:
  1023  		return 4 * len(data), nil
  1024  	case []float64:
  1025  		return 8 * len(data), nil
  1026  	}
  1027  	return 0, nil
  1028  }
  1029  
  1030  // ensure grows buf to length len(buf) + n and returns the grown buffer
  1031  // and a slice starting at the original length of buf (that is, buf2[len(buf):]).
  1032  func ensure(buf []byte, n int) (buf2, pos []byte) {
  1033  	l := len(buf)
  1034  	buf = slices.Grow(buf, n)[:l+n]
  1035  	return buf, buf[l:]
  1036  }
  1037  

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