github.com/ader1990/go@v0.0.0-20140630135419-8c24447fa791/src/pkg/encoding/binary/binary.go (about)

     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 (int8, uint8, int16, float32, complex64, ...)
    11  // or an array or struct containing only fixed-size values.
    12  //
    13  // Varints are a method of encoding integers using one or more bytes;
    14  // numbers with smaller absolute value take a smaller number of bytes.
    15  // For a specification, see http://code.google.com/apis/protocolbuffers/docs/encoding.html.
    16  //
    17  // This package favors simplicity over efficiency. Clients that require
    18  // high-performance serialization, especially for large data structures,
    19  // should look at more advanced solutions such as the encoding/gob
    20  // package or protocol buffers.
    21  package binary
    22  
    23  import (
    24  	"errors"
    25  	"io"
    26  	"math"
    27  	"reflect"
    28  )
    29  
    30  // A ByteOrder specifies how to convert byte sequences into
    31  // 16-, 32-, or 64-bit unsigned integers.
    32  type ByteOrder interface {
    33  	Uint16([]byte) uint16
    34  	Uint32([]byte) uint32
    35  	Uint64([]byte) uint64
    36  	PutUint16([]byte, uint16)
    37  	PutUint32([]byte, uint32)
    38  	PutUint64([]byte, uint64)
    39  	String() string
    40  }
    41  
    42  // LittleEndian is the little-endian implementation of ByteOrder.
    43  var LittleEndian littleEndian
    44  
    45  // BigEndian is the big-endian implementation of ByteOrder.
    46  var BigEndian bigEndian
    47  
    48  type littleEndian struct{}
    49  
    50  func (littleEndian) Uint16(b []byte) uint16 { return uint16(b[0]) | uint16(b[1])<<8 }
    51  
    52  func (littleEndian) PutUint16(b []byte, v uint16) {
    53  	b[0] = byte(v)
    54  	b[1] = byte(v >> 8)
    55  }
    56  
    57  func (littleEndian) Uint32(b []byte) uint32 {
    58  	return uint32(b[0]) | uint32(b[1])<<8 | uint32(b[2])<<16 | uint32(b[3])<<24
    59  }
    60  
    61  func (littleEndian) PutUint32(b []byte, v uint32) {
    62  	b[0] = byte(v)
    63  	b[1] = byte(v >> 8)
    64  	b[2] = byte(v >> 16)
    65  	b[3] = byte(v >> 24)
    66  }
    67  
    68  func (littleEndian) Uint64(b []byte) uint64 {
    69  	return uint64(b[0]) | uint64(b[1])<<8 | uint64(b[2])<<16 | uint64(b[3])<<24 |
    70  		uint64(b[4])<<32 | uint64(b[5])<<40 | uint64(b[6])<<48 | uint64(b[7])<<56
    71  }
    72  
    73  func (littleEndian) PutUint64(b []byte, v uint64) {
    74  	b[0] = byte(v)
    75  	b[1] = byte(v >> 8)
    76  	b[2] = byte(v >> 16)
    77  	b[3] = byte(v >> 24)
    78  	b[4] = byte(v >> 32)
    79  	b[5] = byte(v >> 40)
    80  	b[6] = byte(v >> 48)
    81  	b[7] = byte(v >> 56)
    82  }
    83  
    84  func (littleEndian) String() string { return "LittleEndian" }
    85  
    86  func (littleEndian) GoString() string { return "binary.LittleEndian" }
    87  
    88  type bigEndian struct{}
    89  
    90  func (bigEndian) Uint16(b []byte) uint16 { return uint16(b[1]) | uint16(b[0])<<8 }
    91  
    92  func (bigEndian) PutUint16(b []byte, v uint16) {
    93  	b[0] = byte(v >> 8)
    94  	b[1] = byte(v)
    95  }
    96  
    97  func (bigEndian) Uint32(b []byte) uint32 {
    98  	return uint32(b[3]) | uint32(b[2])<<8 | uint32(b[1])<<16 | uint32(b[0])<<24
    99  }
   100  
   101  func (bigEndian) PutUint32(b []byte, v uint32) {
   102  	b[0] = byte(v >> 24)
   103  	b[1] = byte(v >> 16)
   104  	b[2] = byte(v >> 8)
   105  	b[3] = byte(v)
   106  }
   107  
   108  func (bigEndian) Uint64(b []byte) uint64 {
   109  	return uint64(b[7]) | uint64(b[6])<<8 | uint64(b[5])<<16 | uint64(b[4])<<24 |
   110  		uint64(b[3])<<32 | uint64(b[2])<<40 | uint64(b[1])<<48 | uint64(b[0])<<56
   111  }
   112  
   113  func (bigEndian) PutUint64(b []byte, v uint64) {
   114  	b[0] = byte(v >> 56)
   115  	b[1] = byte(v >> 48)
   116  	b[2] = byte(v >> 40)
   117  	b[3] = byte(v >> 32)
   118  	b[4] = byte(v >> 24)
   119  	b[5] = byte(v >> 16)
   120  	b[6] = byte(v >> 8)
   121  	b[7] = byte(v)
   122  }
   123  
   124  func (bigEndian) String() string { return "BigEndian" }
   125  
   126  func (bigEndian) GoString() string { return "binary.BigEndian" }
   127  
   128  // Read reads structured binary data from r into data.
   129  // Data must be a pointer to a fixed-size value or a slice
   130  // of fixed-size values.
   131  // Bytes read from r are decoded using the specified byte order
   132  // and written to successive fields of the data.
   133  // When reading into structs, the field data for fields with
   134  // blank (_) field names is skipped; i.e., blank field names
   135  // may be used for padding.
   136  // When reading into a struct, all non-blank fields must be exported.
   137  func Read(r io.Reader, order ByteOrder, data interface{}) error {
   138  	// Fast path for basic types and slices.
   139  	if n := intDataSize(data); n != 0 {
   140  		var b [8]byte
   141  		var bs []byte
   142  		if n > len(b) {
   143  			bs = make([]byte, n)
   144  		} else {
   145  			bs = b[:n]
   146  		}
   147  		if _, err := io.ReadFull(r, bs); err != nil {
   148  			return err
   149  		}
   150  		switch data := data.(type) {
   151  		case *int8:
   152  			*data = int8(b[0])
   153  		case *uint8:
   154  			*data = b[0]
   155  		case *int16:
   156  			*data = int16(order.Uint16(bs))
   157  		case *uint16:
   158  			*data = order.Uint16(bs)
   159  		case *int32:
   160  			*data = int32(order.Uint32(bs))
   161  		case *uint32:
   162  			*data = order.Uint32(bs)
   163  		case *int64:
   164  			*data = int64(order.Uint64(bs))
   165  		case *uint64:
   166  			*data = order.Uint64(bs)
   167  		case []int8:
   168  			for i, x := range bs { // Easier to loop over the input for 8-bit values.
   169  				data[i] = int8(x)
   170  			}
   171  		case []uint8:
   172  			copy(data, bs)
   173  		case []int16:
   174  			for i := range data {
   175  				data[i] = int16(order.Uint16(bs[2*i:]))
   176  			}
   177  		case []uint16:
   178  			for i := range data {
   179  				data[i] = order.Uint16(bs[2*i:])
   180  			}
   181  		case []int32:
   182  			for i := range data {
   183  				data[i] = int32(order.Uint32(bs[4*i:]))
   184  			}
   185  		case []uint32:
   186  			for i := range data {
   187  				data[i] = order.Uint32(bs[4*i:])
   188  			}
   189  		case []int64:
   190  			for i := range data {
   191  				data[i] = int64(order.Uint64(bs[8*i:]))
   192  			}
   193  		case []uint64:
   194  			for i := range data {
   195  				data[i] = order.Uint64(bs[8*i:])
   196  			}
   197  		}
   198  		return nil
   199  	}
   200  
   201  	// Fallback to reflect-based decoding.
   202  	var v reflect.Value
   203  	switch d := reflect.ValueOf(data); d.Kind() {
   204  	case reflect.Ptr:
   205  		v = d.Elem()
   206  	case reflect.Slice:
   207  		v = d
   208  	default:
   209  		return errors.New("binary.Read: invalid type " + d.Type().String())
   210  	}
   211  	size, err := dataSize(v)
   212  	if err != nil {
   213  		return errors.New("binary.Read: " + err.Error())
   214  	}
   215  	d := &decoder{order: order, buf: make([]byte, size)}
   216  	if _, err := io.ReadFull(r, d.buf); err != nil {
   217  		return err
   218  	}
   219  	d.value(v)
   220  	return nil
   221  }
   222  
   223  // Write writes the binary representation of data into w.
   224  // Data must be a fixed-size value or a slice of fixed-size
   225  // values, or a pointer to such data.
   226  // Bytes written to w are encoded using the specified byte order
   227  // and read from successive fields of the data.
   228  // When writing structs, zero values are written for fields
   229  // with blank (_) field names.
   230  func Write(w io.Writer, order ByteOrder, data interface{}) error {
   231  	// Fast path for basic types and slices.
   232  	if n := intDataSize(data); n != 0 {
   233  		var b [8]byte
   234  		var bs []byte
   235  		if n > len(b) {
   236  			bs = make([]byte, n)
   237  		} else {
   238  			bs = b[:n]
   239  		}
   240  		switch v := data.(type) {
   241  		case *int8:
   242  			bs = b[:1]
   243  			b[0] = byte(*v)
   244  		case int8:
   245  			bs = b[:1]
   246  			b[0] = byte(v)
   247  		case []int8:
   248  			for i, x := range v {
   249  				bs[i] = byte(x)
   250  			}
   251  		case *uint8:
   252  			bs = b[:1]
   253  			b[0] = *v
   254  		case uint8:
   255  			bs = b[:1]
   256  			b[0] = byte(v)
   257  		case []uint8:
   258  			bs = v
   259  		case *int16:
   260  			bs = b[:2]
   261  			order.PutUint16(bs, uint16(*v))
   262  		case int16:
   263  			bs = b[:2]
   264  			order.PutUint16(bs, uint16(v))
   265  		case []int16:
   266  			for i, x := range v {
   267  				order.PutUint16(bs[2*i:], uint16(x))
   268  			}
   269  		case *uint16:
   270  			bs = b[:2]
   271  			order.PutUint16(bs, *v)
   272  		case uint16:
   273  			bs = b[:2]
   274  			order.PutUint16(bs, v)
   275  		case []uint16:
   276  			for i, x := range v {
   277  				order.PutUint16(bs[2*i:], x)
   278  			}
   279  		case *int32:
   280  			bs = b[:4]
   281  			order.PutUint32(bs, uint32(*v))
   282  		case int32:
   283  			bs = b[:4]
   284  			order.PutUint32(bs, uint32(v))
   285  		case []int32:
   286  			for i, x := range v {
   287  				order.PutUint32(bs[4*i:], uint32(x))
   288  			}
   289  		case *uint32:
   290  			bs = b[:4]
   291  			order.PutUint32(bs, *v)
   292  		case uint32:
   293  			bs = b[:4]
   294  			order.PutUint32(bs, v)
   295  		case []uint32:
   296  			for i, x := range v {
   297  				order.PutUint32(bs[4*i:], x)
   298  			}
   299  		case *int64:
   300  			bs = b[:8]
   301  			order.PutUint64(bs, uint64(*v))
   302  		case int64:
   303  			bs = b[:8]
   304  			order.PutUint64(bs, uint64(v))
   305  		case []int64:
   306  			for i, x := range v {
   307  				order.PutUint64(bs[8*i:], uint64(x))
   308  			}
   309  		case *uint64:
   310  			bs = b[:8]
   311  			order.PutUint64(bs, *v)
   312  		case uint64:
   313  			bs = b[:8]
   314  			order.PutUint64(bs, v)
   315  		case []uint64:
   316  			for i, x := range v {
   317  				order.PutUint64(bs[8*i:], x)
   318  			}
   319  		}
   320  		_, err := w.Write(bs)
   321  		return err
   322  	}
   323  
   324  	// Fallback to reflect-based encoding.
   325  	v := reflect.Indirect(reflect.ValueOf(data))
   326  	size, err := dataSize(v)
   327  	if err != nil {
   328  		return errors.New("binary.Write: " + err.Error())
   329  	}
   330  	buf := make([]byte, size)
   331  	e := &encoder{order: order, buf: buf}
   332  	e.value(v)
   333  	_, err = w.Write(buf)
   334  	return err
   335  }
   336  
   337  // Size returns how many bytes Write would generate to encode the value v, which
   338  // must be a fixed-size value or a slice of fixed-size values, or a pointer to such data.
   339  func Size(v interface{}) int {
   340  	n, err := dataSize(reflect.Indirect(reflect.ValueOf(v)))
   341  	if err != nil {
   342  		return -1
   343  	}
   344  	return n
   345  }
   346  
   347  // dataSize returns the number of bytes the actual data represented by v occupies in memory.
   348  // For compound structures, it sums the sizes of the elements. Thus, for instance, for a slice
   349  // it returns the length of the slice times the element size and does not count the memory
   350  // occupied by the header.
   351  func dataSize(v reflect.Value) (int, error) {
   352  	if v.Kind() == reflect.Slice {
   353  		elem, err := sizeof(v.Type().Elem())
   354  		if err != nil {
   355  			return 0, err
   356  		}
   357  		return v.Len() * elem, nil
   358  	}
   359  	return sizeof(v.Type())
   360  }
   361  
   362  func sizeof(t reflect.Type) (int, error) {
   363  	switch t.Kind() {
   364  	case reflect.Array:
   365  		n, err := sizeof(t.Elem())
   366  		if err != nil {
   367  			return 0, err
   368  		}
   369  		return t.Len() * n, nil
   370  
   371  	case reflect.Struct:
   372  		sum := 0
   373  		for i, n := 0, t.NumField(); i < n; i++ {
   374  			s, err := sizeof(t.Field(i).Type)
   375  			if err != nil {
   376  				return 0, err
   377  			}
   378  			sum += s
   379  		}
   380  		return sum, nil
   381  
   382  	case reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64,
   383  		reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
   384  		reflect.Float32, reflect.Float64, reflect.Complex64, reflect.Complex128:
   385  		return int(t.Size()), nil
   386  	}
   387  	return 0, errors.New("invalid type " + t.String())
   388  }
   389  
   390  type coder struct {
   391  	order ByteOrder
   392  	buf   []byte
   393  }
   394  
   395  type decoder coder
   396  type encoder coder
   397  
   398  func (d *decoder) uint8() uint8 {
   399  	x := d.buf[0]
   400  	d.buf = d.buf[1:]
   401  	return x
   402  }
   403  
   404  func (e *encoder) uint8(x uint8) {
   405  	e.buf[0] = x
   406  	e.buf = e.buf[1:]
   407  }
   408  
   409  func (d *decoder) uint16() uint16 {
   410  	x := d.order.Uint16(d.buf[0:2])
   411  	d.buf = d.buf[2:]
   412  	return x
   413  }
   414  
   415  func (e *encoder) uint16(x uint16) {
   416  	e.order.PutUint16(e.buf[0:2], x)
   417  	e.buf = e.buf[2:]
   418  }
   419  
   420  func (d *decoder) uint32() uint32 {
   421  	x := d.order.Uint32(d.buf[0:4])
   422  	d.buf = d.buf[4:]
   423  	return x
   424  }
   425  
   426  func (e *encoder) uint32(x uint32) {
   427  	e.order.PutUint32(e.buf[0:4], x)
   428  	e.buf = e.buf[4:]
   429  }
   430  
   431  func (d *decoder) uint64() uint64 {
   432  	x := d.order.Uint64(d.buf[0:8])
   433  	d.buf = d.buf[8:]
   434  	return x
   435  }
   436  
   437  func (e *encoder) uint64(x uint64) {
   438  	e.order.PutUint64(e.buf[0:8], x)
   439  	e.buf = e.buf[8:]
   440  }
   441  
   442  func (d *decoder) int8() int8 { return int8(d.uint8()) }
   443  
   444  func (e *encoder) int8(x int8) { e.uint8(uint8(x)) }
   445  
   446  func (d *decoder) int16() int16 { return int16(d.uint16()) }
   447  
   448  func (e *encoder) int16(x int16) { e.uint16(uint16(x)) }
   449  
   450  func (d *decoder) int32() int32 { return int32(d.uint32()) }
   451  
   452  func (e *encoder) int32(x int32) { e.uint32(uint32(x)) }
   453  
   454  func (d *decoder) int64() int64 { return int64(d.uint64()) }
   455  
   456  func (e *encoder) int64(x int64) { e.uint64(uint64(x)) }
   457  
   458  func (d *decoder) value(v reflect.Value) {
   459  	switch v.Kind() {
   460  	case reflect.Array:
   461  		l := v.Len()
   462  		for i := 0; i < l; i++ {
   463  			d.value(v.Index(i))
   464  		}
   465  
   466  	case reflect.Struct:
   467  		t := v.Type()
   468  		l := v.NumField()
   469  		for i := 0; i < l; i++ {
   470  			// Note: Calling v.CanSet() below is an optimization.
   471  			// It would be sufficient to check the field name,
   472  			// but creating the StructField info for each field is
   473  			// costly (run "go test -bench=ReadStruct" and compare
   474  			// results when making changes to this code).
   475  			if v := v.Field(i); v.CanSet() || t.Field(i).Name != "_" {
   476  				d.value(v)
   477  			} else {
   478  				d.skip(v)
   479  			}
   480  		}
   481  
   482  	case reflect.Slice:
   483  		l := v.Len()
   484  		for i := 0; i < l; i++ {
   485  			d.value(v.Index(i))
   486  		}
   487  
   488  	case reflect.Int8:
   489  		v.SetInt(int64(d.int8()))
   490  	case reflect.Int16:
   491  		v.SetInt(int64(d.int16()))
   492  	case reflect.Int32:
   493  		v.SetInt(int64(d.int32()))
   494  	case reflect.Int64:
   495  		v.SetInt(d.int64())
   496  
   497  	case reflect.Uint8:
   498  		v.SetUint(uint64(d.uint8()))
   499  	case reflect.Uint16:
   500  		v.SetUint(uint64(d.uint16()))
   501  	case reflect.Uint32:
   502  		v.SetUint(uint64(d.uint32()))
   503  	case reflect.Uint64:
   504  		v.SetUint(d.uint64())
   505  
   506  	case reflect.Float32:
   507  		v.SetFloat(float64(math.Float32frombits(d.uint32())))
   508  	case reflect.Float64:
   509  		v.SetFloat(math.Float64frombits(d.uint64()))
   510  
   511  	case reflect.Complex64:
   512  		v.SetComplex(complex(
   513  			float64(math.Float32frombits(d.uint32())),
   514  			float64(math.Float32frombits(d.uint32())),
   515  		))
   516  	case reflect.Complex128:
   517  		v.SetComplex(complex(
   518  			math.Float64frombits(d.uint64()),
   519  			math.Float64frombits(d.uint64()),
   520  		))
   521  	}
   522  }
   523  
   524  func (e *encoder) value(v reflect.Value) {
   525  	switch v.Kind() {
   526  	case reflect.Array:
   527  		l := v.Len()
   528  		for i := 0; i < l; i++ {
   529  			e.value(v.Index(i))
   530  		}
   531  
   532  	case reflect.Struct:
   533  		t := v.Type()
   534  		l := v.NumField()
   535  		for i := 0; i < l; i++ {
   536  			// see comment for corresponding code in decoder.value()
   537  			if v := v.Field(i); v.CanSet() || t.Field(i).Name != "_" {
   538  				e.value(v)
   539  			} else {
   540  				e.skip(v)
   541  			}
   542  		}
   543  
   544  	case reflect.Slice:
   545  		l := v.Len()
   546  		for i := 0; i < l; i++ {
   547  			e.value(v.Index(i))
   548  		}
   549  
   550  	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
   551  		switch v.Type().Kind() {
   552  		case reflect.Int8:
   553  			e.int8(int8(v.Int()))
   554  		case reflect.Int16:
   555  			e.int16(int16(v.Int()))
   556  		case reflect.Int32:
   557  			e.int32(int32(v.Int()))
   558  		case reflect.Int64:
   559  			e.int64(v.Int())
   560  		}
   561  
   562  	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
   563  		switch v.Type().Kind() {
   564  		case reflect.Uint8:
   565  			e.uint8(uint8(v.Uint()))
   566  		case reflect.Uint16:
   567  			e.uint16(uint16(v.Uint()))
   568  		case reflect.Uint32:
   569  			e.uint32(uint32(v.Uint()))
   570  		case reflect.Uint64:
   571  			e.uint64(v.Uint())
   572  		}
   573  
   574  	case reflect.Float32, reflect.Float64:
   575  		switch v.Type().Kind() {
   576  		case reflect.Float32:
   577  			e.uint32(math.Float32bits(float32(v.Float())))
   578  		case reflect.Float64:
   579  			e.uint64(math.Float64bits(v.Float()))
   580  		}
   581  
   582  	case reflect.Complex64, reflect.Complex128:
   583  		switch v.Type().Kind() {
   584  		case reflect.Complex64:
   585  			x := v.Complex()
   586  			e.uint32(math.Float32bits(float32(real(x))))
   587  			e.uint32(math.Float32bits(float32(imag(x))))
   588  		case reflect.Complex128:
   589  			x := v.Complex()
   590  			e.uint64(math.Float64bits(real(x)))
   591  			e.uint64(math.Float64bits(imag(x)))
   592  		}
   593  	}
   594  }
   595  
   596  func (d *decoder) skip(v reflect.Value) {
   597  	n, _ := dataSize(v)
   598  	d.buf = d.buf[n:]
   599  }
   600  
   601  func (e *encoder) skip(v reflect.Value) {
   602  	n, _ := dataSize(v)
   603  	for i := range e.buf[0:n] {
   604  		e.buf[i] = 0
   605  	}
   606  	e.buf = e.buf[n:]
   607  }
   608  
   609  // intDataSize returns the size of the data required to represent the data when encoded.
   610  // It returns zero if the type cannot be implemented by the fast path in Read or Write.
   611  func intDataSize(data interface{}) int {
   612  	switch data := data.(type) {
   613  	case int8, *int8, *uint8:
   614  		return 1
   615  	case []int8:
   616  		return len(data)
   617  	case []uint8:
   618  		return len(data)
   619  	case int16, *int16, *uint16:
   620  		return 2
   621  	case []int16:
   622  		return 2 * len(data)
   623  	case []uint16:
   624  		return 2 * len(data)
   625  	case int32, *int32, *uint32:
   626  		return 4
   627  	case []int32:
   628  		return 4 * len(data)
   629  	case []uint32:
   630  		return 4 * len(data)
   631  	case int64, *int64, *uint64:
   632  		return 8
   633  	case []int64:
   634  		return 8 * len(data)
   635  	case []uint64:
   636  		return 8 * len(data)
   637  	}
   638  	return 0
   639  }