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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 protocol buffers.
    22  package binary
    23  
    24  import (
    25  	"errors"
    26  	"io"
    27  	"math"
    28  	"reflect"
    29  )
    30  
    31  // A ByteOrder specifies how to convert byte sequences into
    32  // 16-, 32-, or 64-bit unsigned integers.
    33  type ByteOrder interface {
    34  	Uint16([]byte) uint16
    35  	Uint32([]byte) uint32
    36  	Uint64([]byte) uint64
    37  	PutUint16([]byte, uint16)
    38  	PutUint32([]byte, uint32)
    39  	PutUint64([]byte, uint64)
    40  	String() string
    41  }
    42  
    43  // LittleEndian is the little-endian implementation of ByteOrder.
    44  var LittleEndian littleEndian
    45  
    46  // BigEndian is the big-endian implementation of ByteOrder.
    47  var BigEndian bigEndian
    48  
    49  type littleEndian struct{}
    50  
    51  func (littleEndian) Uint16(b []byte) uint16 {
    52  	_ = b[1] // bounds check hint to compiler; see golang.org/issue/14808
    53  	return uint16(b[0]) | uint16(b[1])<<8
    54  }
    55  
    56  func (littleEndian) PutUint16(b []byte, v uint16) {
    57  	_ = b[1] // early bounds check to guarantee safety of writes below
    58  	b[0] = byte(v)
    59  	b[1] = byte(v >> 8)
    60  }
    61  
    62  func (littleEndian) Uint32(b []byte) uint32 {
    63  	_ = b[3] // bounds check hint to compiler; see golang.org/issue/14808
    64  	return uint32(b[0]) | uint32(b[1])<<8 | uint32(b[2])<<16 | uint32(b[3])<<24
    65  }
    66  
    67  func (littleEndian) PutUint32(b []byte, v uint32) {
    68  	_ = b[3] // early bounds check to guarantee safety of writes below
    69  	b[0] = byte(v)
    70  	b[1] = byte(v >> 8)
    71  	b[2] = byte(v >> 16)
    72  	b[3] = byte(v >> 24)
    73  }
    74  
    75  func (littleEndian) Uint64(b []byte) uint64 {
    76  	_ = b[7] // bounds check hint to compiler; see golang.org/issue/14808
    77  	return uint64(b[0]) | uint64(b[1])<<8 | uint64(b[2])<<16 | uint64(b[3])<<24 |
    78  		uint64(b[4])<<32 | uint64(b[5])<<40 | uint64(b[6])<<48 | uint64(b[7])<<56
    79  }
    80  
    81  func (littleEndian) PutUint64(b []byte, v uint64) {
    82  	_ = b[7] // early bounds check to guarantee safety of writes below
    83  	b[0] = byte(v)
    84  	b[1] = byte(v >> 8)
    85  	b[2] = byte(v >> 16)
    86  	b[3] = byte(v >> 24)
    87  	b[4] = byte(v >> 32)
    88  	b[5] = byte(v >> 40)
    89  	b[6] = byte(v >> 48)
    90  	b[7] = byte(v >> 56)
    91  }
    92  
    93  func (littleEndian) String() string { return "LittleEndian" }
    94  
    95  func (littleEndian) GoString() string { return "binary.LittleEndian" }
    96  
    97  type bigEndian struct{}
    98  
    99  func (bigEndian) Uint16(b []byte) uint16 {
   100  	_ = b[1] // bounds check hint to compiler; see golang.org/issue/14808
   101  	return uint16(b[1]) | uint16(b[0])<<8
   102  }
   103  
   104  func (bigEndian) PutUint16(b []byte, v uint16) {
   105  	_ = b[1] // early bounds check to guarantee safety of writes below
   106  	b[0] = byte(v >> 8)
   107  	b[1] = byte(v)
   108  }
   109  
   110  func (bigEndian) Uint32(b []byte) uint32 {
   111  	_ = b[3] // bounds check hint to compiler; see golang.org/issue/14808
   112  	return uint32(b[3]) | uint32(b[2])<<8 | uint32(b[1])<<16 | uint32(b[0])<<24
   113  }
   114  
   115  func (bigEndian) PutUint32(b []byte, v uint32) {
   116  	_ = b[3] // early bounds check to guarantee safety of writes below
   117  	b[0] = byte(v >> 24)
   118  	b[1] = byte(v >> 16)
   119  	b[2] = byte(v >> 8)
   120  	b[3] = byte(v)
   121  }
   122  
   123  func (bigEndian) Uint64(b []byte) uint64 {
   124  	_ = b[7] // bounds check hint to compiler; see golang.org/issue/14808
   125  	return uint64(b[7]) | uint64(b[6])<<8 | uint64(b[5])<<16 | uint64(b[4])<<24 |
   126  		uint64(b[3])<<32 | uint64(b[2])<<40 | uint64(b[1])<<48 | uint64(b[0])<<56
   127  }
   128  
   129  func (bigEndian) PutUint64(b []byte, v uint64) {
   130  	_ = b[7] // early bounds check to guarantee safety of writes below
   131  	b[0] = byte(v >> 56)
   132  	b[1] = byte(v >> 48)
   133  	b[2] = byte(v >> 40)
   134  	b[3] = byte(v >> 32)
   135  	b[4] = byte(v >> 24)
   136  	b[5] = byte(v >> 16)
   137  	b[6] = byte(v >> 8)
   138  	b[7] = byte(v)
   139  }
   140  
   141  func (bigEndian) String() string { return "BigEndian" }
   142  
   143  func (bigEndian) GoString() string { return "binary.BigEndian" }
   144  
   145  // Read reads structured binary data from r into data.
   146  // Data must be a pointer to a fixed-size value or a slice
   147  // of fixed-size values.
   148  // Bytes read from r are decoded using the specified byte order
   149  // and written to successive fields of the data.
   150  // When decoding boolean values, a zero byte is decoded as false, and
   151  // any other non-zero byte is decoded as true.
   152  // When reading into structs, the field data for fields with
   153  // blank (_) field names is skipped; i.e., blank field names
   154  // may be used for padding.
   155  // When reading into a struct, all non-blank fields must be exported
   156  // or Read may panic.
   157  //
   158  // The error is EOF only if no bytes were read.
   159  // If an EOF happens after reading some but not all the bytes,
   160  // Read returns ErrUnexpectedEOF.
   161  func Read(r io.Reader, order ByteOrder, data interface{}) error {
   162  	// Fast path for basic types and slices.
   163  	if n := intDataSize(data); n != 0 {
   164  		bs := make([]byte, n)
   165  		if _, err := io.ReadFull(r, bs); err != nil {
   166  			return err
   167  		}
   168  		switch data := data.(type) {
   169  		case *bool:
   170  			*data = bs[0] != 0
   171  		case *int8:
   172  			*data = int8(bs[0])
   173  		case *uint8:
   174  			*data = bs[0]
   175  		case *int16:
   176  			*data = int16(order.Uint16(bs))
   177  		case *uint16:
   178  			*data = order.Uint16(bs)
   179  		case *int32:
   180  			*data = int32(order.Uint32(bs))
   181  		case *uint32:
   182  			*data = order.Uint32(bs)
   183  		case *int64:
   184  			*data = int64(order.Uint64(bs))
   185  		case *uint64:
   186  			*data = order.Uint64(bs)
   187  		case []bool:
   188  			for i, x := range bs { // Easier to loop over the input for 8-bit values.
   189  				data[i] = x != 0
   190  			}
   191  		case []int8:
   192  			for i, x := range bs {
   193  				data[i] = int8(x)
   194  			}
   195  		case []uint8:
   196  			copy(data, bs)
   197  		case []int16:
   198  			for i := range data {
   199  				data[i] = int16(order.Uint16(bs[2*i:]))
   200  			}
   201  		case []uint16:
   202  			for i := range data {
   203  				data[i] = order.Uint16(bs[2*i:])
   204  			}
   205  		case []int32:
   206  			for i := range data {
   207  				data[i] = int32(order.Uint32(bs[4*i:]))
   208  			}
   209  		case []uint32:
   210  			for i := range data {
   211  				data[i] = order.Uint32(bs[4*i:])
   212  			}
   213  		case []int64:
   214  			for i := range data {
   215  				data[i] = int64(order.Uint64(bs[8*i:]))
   216  			}
   217  		case []uint64:
   218  			for i := range data {
   219  				data[i] = order.Uint64(bs[8*i:])
   220  			}
   221  		}
   222  		return nil
   223  	}
   224  
   225  	// Fallback to reflect-based decoding.
   226  	v := reflect.ValueOf(data)
   227  	size := -1
   228  	switch v.Kind() {
   229  	case reflect.Ptr:
   230  		v = v.Elem()
   231  		size = dataSize(v)
   232  	case reflect.Slice:
   233  		size = dataSize(v)
   234  	}
   235  	if size < 0 {
   236  		return errors.New("binary.Read: invalid type " + reflect.TypeOf(data).String())
   237  	}
   238  	d := &decoder{order: order, buf: make([]byte, size)}
   239  	if _, err := io.ReadFull(r, d.buf); err != nil {
   240  		return err
   241  	}
   242  	d.value(v)
   243  	return nil
   244  }
   245  
   246  // Write writes the binary representation of data into w.
   247  // Data must be a fixed-size value or a slice of fixed-size
   248  // values, or a pointer to such data.
   249  // Boolean values encode as one byte: 1 for true, and 0 for false.
   250  // Bytes written to w are encoded using the specified byte order
   251  // and read from successive fields of the data.
   252  // When writing structs, zero values are written for fields
   253  // with blank (_) field names.
   254  func Write(w io.Writer, order ByteOrder, data interface{}) error {
   255  	// Fast path for basic types and slices.
   256  	if n := intDataSize(data); n != 0 {
   257  		bs := make([]byte, n)
   258  		switch v := data.(type) {
   259  		case *bool:
   260  			if *v {
   261  				bs[0] = 1
   262  			} else {
   263  				bs[0] = 0
   264  			}
   265  		case bool:
   266  			if v {
   267  				bs[0] = 1
   268  			} else {
   269  				bs[0] = 0
   270  			}
   271  		case []bool:
   272  			for i, x := range v {
   273  				if x {
   274  					bs[i] = 1
   275  				} else {
   276  					bs[i] = 0
   277  				}
   278  			}
   279  		case *int8:
   280  			bs[0] = byte(*v)
   281  		case int8:
   282  			bs[0] = byte(v)
   283  		case []int8:
   284  			for i, x := range v {
   285  				bs[i] = byte(x)
   286  			}
   287  		case *uint8:
   288  			bs[0] = *v
   289  		case uint8:
   290  			bs[0] = v
   291  		case []uint8:
   292  			bs = v // TODO(josharian): avoid allocating bs in this case?
   293  		case *int16:
   294  			order.PutUint16(bs, uint16(*v))
   295  		case int16:
   296  			order.PutUint16(bs, uint16(v))
   297  		case []int16:
   298  			for i, x := range v {
   299  				order.PutUint16(bs[2*i:], uint16(x))
   300  			}
   301  		case *uint16:
   302  			order.PutUint16(bs, *v)
   303  		case uint16:
   304  			order.PutUint16(bs, v)
   305  		case []uint16:
   306  			for i, x := range v {
   307  				order.PutUint16(bs[2*i:], x)
   308  			}
   309  		case *int32:
   310  			order.PutUint32(bs, uint32(*v))
   311  		case int32:
   312  			order.PutUint32(bs, uint32(v))
   313  		case []int32:
   314  			for i, x := range v {
   315  				order.PutUint32(bs[4*i:], uint32(x))
   316  			}
   317  		case *uint32:
   318  			order.PutUint32(bs, *v)
   319  		case uint32:
   320  			order.PutUint32(bs, v)
   321  		case []uint32:
   322  			for i, x := range v {
   323  				order.PutUint32(bs[4*i:], x)
   324  			}
   325  		case *int64:
   326  			order.PutUint64(bs, uint64(*v))
   327  		case int64:
   328  			order.PutUint64(bs, uint64(v))
   329  		case []int64:
   330  			for i, x := range v {
   331  				order.PutUint64(bs[8*i:], uint64(x))
   332  			}
   333  		case *uint64:
   334  			order.PutUint64(bs, *v)
   335  		case uint64:
   336  			order.PutUint64(bs, v)
   337  		case []uint64:
   338  			for i, x := range v {
   339  				order.PutUint64(bs[8*i:], x)
   340  			}
   341  		}
   342  		_, err := w.Write(bs)
   343  		return err
   344  	}
   345  
   346  	// Fallback to reflect-based encoding.
   347  	v := reflect.Indirect(reflect.ValueOf(data))
   348  	size := dataSize(v)
   349  	if size < 0 {
   350  		return errors.New("binary.Write: invalid type " + reflect.TypeOf(data).String())
   351  	}
   352  	buf := make([]byte, size)
   353  	e := &encoder{order: order, buf: buf}
   354  	e.value(v)
   355  	_, err := w.Write(buf)
   356  	return err
   357  }
   358  
   359  // Size returns how many bytes Write would generate to encode the value v, which
   360  // must be a fixed-size value or a slice of fixed-size values, or a pointer to such data.
   361  // If v is neither of these, Size returns -1.
   362  func Size(v interface{}) int {
   363  	return dataSize(reflect.Indirect(reflect.ValueOf(v)))
   364  }
   365  
   366  // dataSize returns the number of bytes the actual data represented by v occupies in memory.
   367  // For compound structures, it sums the sizes of the elements. Thus, for instance, for a slice
   368  // it returns the length of the slice times the element size and does not count the memory
   369  // occupied by the header. If the type of v is not acceptable, dataSize returns -1.
   370  func dataSize(v reflect.Value) int {
   371  	if v.Kind() == reflect.Slice {
   372  		if s := sizeof(v.Type().Elem()); s >= 0 {
   373  			return s * v.Len()
   374  		}
   375  		return -1
   376  	}
   377  	return sizeof(v.Type())
   378  }
   379  
   380  // sizeof returns the size >= 0 of variables for the given type or -1 if the type is not acceptable.
   381  func sizeof(t reflect.Type) int {
   382  	switch t.Kind() {
   383  	case reflect.Array:
   384  		if s := sizeof(t.Elem()); s >= 0 {
   385  			return s * t.Len()
   386  		}
   387  
   388  	case reflect.Struct:
   389  		sum := 0
   390  		for i, n := 0, t.NumField(); i < n; i++ {
   391  			s := sizeof(t.Field(i).Type)
   392  			if s < 0 {
   393  				return -1
   394  			}
   395  			sum += s
   396  		}
   397  		return sum
   398  
   399  	case reflect.Bool,
   400  		reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64,
   401  		reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
   402  		reflect.Float32, reflect.Float64, reflect.Complex64, reflect.Complex128:
   403  		return int(t.Size())
   404  	}
   405  
   406  	return -1
   407  }
   408  
   409  type coder struct {
   410  	order  ByteOrder
   411  	buf    []byte
   412  	offset int
   413  }
   414  
   415  type decoder coder
   416  type encoder coder
   417  
   418  func (d *decoder) bool() bool {
   419  	x := d.buf[d.offset]
   420  	d.offset++
   421  	return x != 0
   422  }
   423  
   424  func (e *encoder) bool(x bool) {
   425  	if x {
   426  		e.buf[e.offset] = 1
   427  	} else {
   428  		e.buf[e.offset] = 0
   429  	}
   430  	e.offset++
   431  }
   432  
   433  func (d *decoder) uint8() uint8 {
   434  	x := d.buf[d.offset]
   435  	d.offset++
   436  	return x
   437  }
   438  
   439  func (e *encoder) uint8(x uint8) {
   440  	e.buf[e.offset] = x
   441  	e.offset++
   442  }
   443  
   444  func (d *decoder) uint16() uint16 {
   445  	x := d.order.Uint16(d.buf[d.offset : d.offset+2])
   446  	d.offset += 2
   447  	return x
   448  }
   449  
   450  func (e *encoder) uint16(x uint16) {
   451  	e.order.PutUint16(e.buf[e.offset:e.offset+2], x)
   452  	e.offset += 2
   453  }
   454  
   455  func (d *decoder) uint32() uint32 {
   456  	x := d.order.Uint32(d.buf[d.offset : d.offset+4])
   457  	d.offset += 4
   458  	return x
   459  }
   460  
   461  func (e *encoder) uint32(x uint32) {
   462  	e.order.PutUint32(e.buf[e.offset:e.offset+4], x)
   463  	e.offset += 4
   464  }
   465  
   466  func (d *decoder) uint64() uint64 {
   467  	x := d.order.Uint64(d.buf[d.offset : d.offset+8])
   468  	d.offset += 8
   469  	return x
   470  }
   471  
   472  func (e *encoder) uint64(x uint64) {
   473  	e.order.PutUint64(e.buf[e.offset:e.offset+8], x)
   474  	e.offset += 8
   475  }
   476  
   477  func (d *decoder) int8() int8 { return int8(d.uint8()) }
   478  
   479  func (e *encoder) int8(x int8) { e.uint8(uint8(x)) }
   480  
   481  func (d *decoder) int16() int16 { return int16(d.uint16()) }
   482  
   483  func (e *encoder) int16(x int16) { e.uint16(uint16(x)) }
   484  
   485  func (d *decoder) int32() int32 { return int32(d.uint32()) }
   486  
   487  func (e *encoder) int32(x int32) { e.uint32(uint32(x)) }
   488  
   489  func (d *decoder) int64() int64 { return int64(d.uint64()) }
   490  
   491  func (e *encoder) int64(x int64) { e.uint64(uint64(x)) }
   492  
   493  func (d *decoder) value(v reflect.Value) {
   494  	switch v.Kind() {
   495  	case reflect.Array:
   496  		l := v.Len()
   497  		for i := 0; i < l; i++ {
   498  			d.value(v.Index(i))
   499  		}
   500  
   501  	case reflect.Struct:
   502  		t := v.Type()
   503  		l := v.NumField()
   504  		for i := 0; i < l; i++ {
   505  			// Note: Calling v.CanSet() below is an optimization.
   506  			// It would be sufficient to check the field name,
   507  			// but creating the StructField info for each field is
   508  			// costly (run "go test -bench=ReadStruct" and compare
   509  			// results when making changes to this code).
   510  			if v := v.Field(i); v.CanSet() || t.Field(i).Name != "_" {
   511  				d.value(v)
   512  			} else {
   513  				d.skip(v)
   514  			}
   515  		}
   516  
   517  	case reflect.Slice:
   518  		l := v.Len()
   519  		for i := 0; i < l; i++ {
   520  			d.value(v.Index(i))
   521  		}
   522  
   523  	case reflect.Bool:
   524  		v.SetBool(d.bool())
   525  
   526  	case reflect.Int8:
   527  		v.SetInt(int64(d.int8()))
   528  	case reflect.Int16:
   529  		v.SetInt(int64(d.int16()))
   530  	case reflect.Int32:
   531  		v.SetInt(int64(d.int32()))
   532  	case reflect.Int64:
   533  		v.SetInt(d.int64())
   534  
   535  	case reflect.Uint8:
   536  		v.SetUint(uint64(d.uint8()))
   537  	case reflect.Uint16:
   538  		v.SetUint(uint64(d.uint16()))
   539  	case reflect.Uint32:
   540  		v.SetUint(uint64(d.uint32()))
   541  	case reflect.Uint64:
   542  		v.SetUint(d.uint64())
   543  
   544  	case reflect.Float32:
   545  		v.SetFloat(float64(math.Float32frombits(d.uint32())))
   546  	case reflect.Float64:
   547  		v.SetFloat(math.Float64frombits(d.uint64()))
   548  
   549  	case reflect.Complex64:
   550  		v.SetComplex(complex(
   551  			float64(math.Float32frombits(d.uint32())),
   552  			float64(math.Float32frombits(d.uint32())),
   553  		))
   554  	case reflect.Complex128:
   555  		v.SetComplex(complex(
   556  			math.Float64frombits(d.uint64()),
   557  			math.Float64frombits(d.uint64()),
   558  		))
   559  	}
   560  }
   561  
   562  func (e *encoder) value(v reflect.Value) {
   563  	switch v.Kind() {
   564  	case reflect.Array:
   565  		l := v.Len()
   566  		for i := 0; i < l; i++ {
   567  			e.value(v.Index(i))
   568  		}
   569  
   570  	case reflect.Struct:
   571  		t := v.Type()
   572  		l := v.NumField()
   573  		for i := 0; i < l; i++ {
   574  			// see comment for corresponding code in decoder.value()
   575  			if v := v.Field(i); v.CanSet() || t.Field(i).Name != "_" {
   576  				e.value(v)
   577  			} else {
   578  				e.skip(v)
   579  			}
   580  		}
   581  
   582  	case reflect.Slice:
   583  		l := v.Len()
   584  		for i := 0; i < l; i++ {
   585  			e.value(v.Index(i))
   586  		}
   587  
   588  	case reflect.Bool:
   589  		e.bool(v.Bool())
   590  
   591  	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
   592  		switch v.Type().Kind() {
   593  		case reflect.Int8:
   594  			e.int8(int8(v.Int()))
   595  		case reflect.Int16:
   596  			e.int16(int16(v.Int()))
   597  		case reflect.Int32:
   598  			e.int32(int32(v.Int()))
   599  		case reflect.Int64:
   600  			e.int64(v.Int())
   601  		}
   602  
   603  	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
   604  		switch v.Type().Kind() {
   605  		case reflect.Uint8:
   606  			e.uint8(uint8(v.Uint()))
   607  		case reflect.Uint16:
   608  			e.uint16(uint16(v.Uint()))
   609  		case reflect.Uint32:
   610  			e.uint32(uint32(v.Uint()))
   611  		case reflect.Uint64:
   612  			e.uint64(v.Uint())
   613  		}
   614  
   615  	case reflect.Float32, reflect.Float64:
   616  		switch v.Type().Kind() {
   617  		case reflect.Float32:
   618  			e.uint32(math.Float32bits(float32(v.Float())))
   619  		case reflect.Float64:
   620  			e.uint64(math.Float64bits(v.Float()))
   621  		}
   622  
   623  	case reflect.Complex64, reflect.Complex128:
   624  		switch v.Type().Kind() {
   625  		case reflect.Complex64:
   626  			x := v.Complex()
   627  			e.uint32(math.Float32bits(float32(real(x))))
   628  			e.uint32(math.Float32bits(float32(imag(x))))
   629  		case reflect.Complex128:
   630  			x := v.Complex()
   631  			e.uint64(math.Float64bits(real(x)))
   632  			e.uint64(math.Float64bits(imag(x)))
   633  		}
   634  	}
   635  }
   636  
   637  func (d *decoder) skip(v reflect.Value) {
   638  	d.offset += dataSize(v)
   639  }
   640  
   641  func (e *encoder) skip(v reflect.Value) {
   642  	n := dataSize(v)
   643  	zero := e.buf[e.offset : e.offset+n]
   644  	for i := range zero {
   645  		zero[i] = 0
   646  	}
   647  	e.offset += n
   648  }
   649  
   650  // intDataSize returns the size of the data required to represent the data when encoded.
   651  // It returns zero if the type cannot be implemented by the fast path in Read or Write.
   652  func intDataSize(data interface{}) int {
   653  	switch data := data.(type) {
   654  	case bool, int8, uint8, *bool, *int8, *uint8:
   655  		return 1
   656  	case []bool:
   657  		return len(data)
   658  	case []int8:
   659  		return len(data)
   660  	case []uint8:
   661  		return len(data)
   662  	case int16, uint16, *int16, *uint16:
   663  		return 2
   664  	case []int16:
   665  		return 2 * len(data)
   666  	case []uint16:
   667  		return 2 * len(data)
   668  	case int32, uint32, *int32, *uint32:
   669  		return 4
   670  	case []int32:
   671  		return 4 * len(data)
   672  	case []uint32:
   673  		return 4 * len(data)
   674  	case int64, uint64, *int64, *uint64:
   675  		return 8
   676  	case []int64:
   677  		return 8 * len(data)
   678  	case []uint64:
   679  		return 8 * len(data)
   680  	}
   681  	return 0
   682  }
   683  

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