Source file src/encoding/binary/binary.go

Documentation: encoding/binary

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

View as plain text