binary.go

Documentation: github.com/shirou/gopsutil/internal/common

     1  package common
     2  
     3  // Copyright 2009 The Go Authors.  All rights reserved.
     4  // Use of this source code is governed by a BSD-style
     5  // license that can be found in the LICENSE file.
     6  
     7  // Package binary implements simple translation between numbers and byte
     8  // sequences and encoding and decoding of varints.
     9  //
    10  // Numbers are translated by reading and writing fixed-size values.
    11  // A fixed-size value is either a fixed-size arithmetic
    12  // type (int8, uint8, int16, float32, complex64, ...)
    13  // or an array or struct containing only fixed-size values.
    14  //
    15  // The varint functions encode and decode single integer values using
    16  // a variable-length encoding; smaller values require fewer bytes.
    17  // For a specification, see
    18  // http://code.google.com/apis/protocolbuffers/docs/encoding.html.
    19  //
    20  // This package favors simplicity over efficiency. Clients that require
    21  // high-performance serialization, especially for large data structures,
    22  // should look at more advanced solutions such as the encoding/gob
    23  // package or protocol buffers.
    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 { return uint16(b[0]) | uint16(b[1])<<8 }
    52  
    53  func (littleEndian) PutUint16(b []byte, v uint16) {
    54  	b[0] = byte(v)
    55  	b[1] = byte(v >> 8)
    56  }
    57  
    58  func (littleEndian) Uint32(b []byte) uint32 {
    59  	return uint32(b[0]) | uint32(b[1])<<8 | uint32(b[2])<<16 | uint32(b[3])<<24
    60  }
    61  
    62  func (littleEndian) PutUint32(b []byte, v uint32) {
    63  	b[0] = byte(v)
    64  	b[1] = byte(v >> 8)
    65  	b[2] = byte(v >> 16)
    66  	b[3] = byte(v >> 24)
    67  }
    68  
    69  func (littleEndian) Uint64(b []byte) uint64 {
    70  	return uint64(b[0]) | uint64(b[1])<<8 | uint64(b[2])<<16 | uint64(b[3])<<24 |
    71  		uint64(b[4])<<32 | uint64(b[5])<<40 | uint64(b[6])<<48 | uint64(b[7])<<56
    72  }
    73  
    74  func (littleEndian) PutUint64(b []byte, v uint64) {
    75  	b[0] = byte(v)
    76  	b[1] = byte(v >> 8)
    77  	b[2] = byte(v >> 16)
    78  	b[3] = byte(v >> 24)
    79  	b[4] = byte(v >> 32)
    80  	b[5] = byte(v >> 40)
    81  	b[6] = byte(v >> 48)
    82  	b[7] = byte(v >> 56)
    83  }
    84  
    85  func (littleEndian) String() string { return "LittleEndian" }
    86  
    87  func (littleEndian) GoString() string { return "binary.LittleEndian" }
    88  
    89  type bigEndian struct{}
    90  
    91  func (bigEndian) Uint16(b []byte) uint16 { return uint16(b[1]) | uint16(b[0])<<8 }
    92  
    93  func (bigEndian) PutUint16(b []byte, v uint16) {
    94  	b[0] = byte(v >> 8)
    95  	b[1] = byte(v)
    96  }
    97  
    98  func (bigEndian) Uint32(b []byte) uint32 {
    99  	return uint32(b[3]) | uint32(b[2])<<8 | uint32(b[1])<<16 | uint32(b[0])<<24
   100  }
   101  
   102  func (bigEndian) PutUint32(b []byte, v uint32) {
   103  	b[0] = byte(v >> 24)
   104  	b[1] = byte(v >> 16)
   105  	b[2] = byte(v >> 8)
   106  	b[3] = byte(v)
   107  }
   108  
   109  func (bigEndian) Uint64(b []byte) uint64 {
   110  	return uint64(b[7]) | uint64(b[6])<<8 | uint64(b[5])<<16 | uint64(b[4])<<24 |
   111  		uint64(b[3])<<32 | uint64(b[2])<<40 | uint64(b[1])<<48 | uint64(b[0])<<56
   112  }
   113  
   114  func (bigEndian) PutUint64(b []byte, v uint64) {
   115  	b[0] = byte(v >> 56)
   116  	b[1] = byte(v >> 48)
   117  	b[2] = byte(v >> 40)
   118  	b[3] = byte(v >> 32)
   119  	b[4] = byte(v >> 24)
   120  	b[5] = byte(v >> 16)
   121  	b[6] = byte(v >> 8)
   122  	b[7] = byte(v)
   123  }
   124  
   125  func (bigEndian) String() string { return "BigEndian" }
   126  
   127  func (bigEndian) GoString() string { return "binary.BigEndian" }
   128  
   129  // Read reads structured binary data from r into data.
   130  // Data must be a pointer to a fixed-size value or a slice
   131  // of fixed-size values.
   132  // Bytes read from r are decoded using the specified byte order
   133  // and written to successive fields of the data.
   134  // When reading into structs, the field data for fields with
   135  // blank (_) field names is skipped; i.e., blank field names
   136  // may be used for padding.
   137  // When reading into a struct, all non-blank fields must be exported.
   138  func Read(r io.Reader, order ByteOrder, data interface{}) error {
   139  	// Fast path for basic types and slices.
   140  	if n := intDataSize(data); n != 0 {
   141  		var b [8]byte
   142  		var bs []byte
   143  		if n > len(b) {
   144  			bs = make([]byte, n)
   145  		} else {
   146  			bs = b[:n]
   147  		}
   148  		if _, err := io.ReadFull(r, bs); err != nil {
   149  			return err
   150  		}
   151  		switch data := data.(type) {
   152  		case *int8:
   153  			*data = int8(b[0])
   154  		case *uint8:
   155  			*data = b[0]
   156  		case *int16:
   157  			*data = int16(order.Uint16(bs))
   158  		case *uint16:
   159  			*data = order.Uint16(bs)
   160  		case *int32:
   161  			*data = int32(order.Uint32(bs))
   162  		case *uint32:
   163  			*data = order.Uint32(bs)
   164  		case *int64:
   165  			*data = int64(order.Uint64(bs))
   166  		case *uint64:
   167  			*data = order.Uint64(bs)
   168  		case []int8:
   169  			for i, x := range bs { // Easier to loop over the input for 8-bit values.
   170  				data[i] = int8(x)
   171  			}
   172  		case []uint8:
   173  			copy(data, bs)
   174  		case []int16:
   175  			for i := range data {
   176  				data[i] = int16(order.Uint16(bs[2*i:]))
   177  			}
   178  		case []uint16:
   179  			for i := range data {
   180  				data[i] = order.Uint16(bs[2*i:])
   181  			}
   182  		case []int32:
   183  			for i := range data {
   184  				data[i] = int32(order.Uint32(bs[4*i:]))
   185  			}
   186  		case []uint32:
   187  			for i := range data {
   188  				data[i] = order.Uint32(bs[4*i:])
   189  			}
   190  		case []int64:
   191  			for i := range data {
   192  				data[i] = int64(order.Uint64(bs[8*i:]))
   193  			}
   194  		case []uint64:
   195  			for i := range data {
   196  				data[i] = order.Uint64(bs[8*i:])
   197  			}
   198  		}
   199  		return nil
   200  	}
   201  
   202  	// Fallback to reflect-based decoding.
   203  	v := reflect.ValueOf(data)
   204  	size := -1
   205  	switch v.Kind() {
   206  	case reflect.Ptr:
   207  		v = v.Elem()
   208  		size = dataSize(v)
   209  	case reflect.Slice:
   210  		size = dataSize(v)
   211  	}
   212  	if size < 0 {
   213  		return errors.New("binary.Read: invalid type " + reflect.TypeOf(data).String())
   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] = 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 := dataSize(v)
   327  	if size < 0 {
   328  		return errors.New("binary.Write: invalid type " + reflect.TypeOf(data).String())
   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  // If v is neither of these, Size returns -1.
   340  func Size(v interface{}) int {
   341  	return dataSize(reflect.Indirect(reflect.ValueOf(v)))
   342  }
   343  
   344  // dataSize returns the number of bytes the actual data represented by v occupies in memory.
   345  // For compound structures, it sums the sizes of the elements. Thus, for instance, for a slice
   346  // it returns the length of the slice times the element size and does not count the memory
   347  // occupied by the header. If the type of v is not acceptable, dataSize returns -1.
   348  func dataSize(v reflect.Value) int {
   349  	if v.Kind() == reflect.Slice {
   350  		if s := sizeof(v.Type().Elem()); s >= 0 {
   351  			return s * v.Len()
   352  		}
   353  		return -1
   354  	}
   355  	return sizeof(v.Type())
   356  }
   357  
   358  // sizeof returns the size >= 0 of variables for the given type or -1 if the type is not acceptable.
   359  func sizeof(t reflect.Type) int {
   360  	switch t.Kind() {
   361  	case reflect.Array:
   362  		if s := sizeof(t.Elem()); s >= 0 {
   363  			return s * t.Len()
   364  		}
   365  
   366  	case reflect.Struct:
   367  		sum := 0
   368  		for i, n := 0, t.NumField(); i < n; i++ {
   369  			s := sizeof(t.Field(i).Type)
   370  			if s < 0 {
   371  				return -1
   372  			}
   373  			sum += s
   374  		}
   375  		return sum
   376  
   377  	case reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64,
   378  		reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
   379  		reflect.Float32, reflect.Float64, reflect.Complex64, reflect.Complex128, reflect.Ptr:
   380  		return int(t.Size())
   381  	}
   382  
   383  	return -1
   384  }
   385  
   386  type coder struct {
   387  	order ByteOrder
   388  	buf   []byte
   389  }
   390  
   391  type decoder coder
   392  type encoder coder
   393  
   394  func (d *decoder) uint8() uint8 {
   395  	x := d.buf[0]
   396  	d.buf = d.buf[1:]
   397  	return x
   398  }
   399  
   400  func (e *encoder) uint8(x uint8) {
   401  	e.buf[0] = x
   402  	e.buf = e.buf[1:]
   403  }
   404  
   405  func (d *decoder) uint16() uint16 {
   406  	x := d.order.Uint16(d.buf[0:2])
   407  	d.buf = d.buf[2:]
   408  	return x
   409  }
   410  
   411  func (e *encoder) uint16(x uint16) {
   412  	e.order.PutUint16(e.buf[0:2], x)
   413  	e.buf = e.buf[2:]
   414  }
   415  
   416  func (d *decoder) uint32() uint32 {
   417  	x := d.order.Uint32(d.buf[0:4])
   418  	d.buf = d.buf[4:]
   419  	return x
   420  }
   421  
   422  func (e *encoder) uint32(x uint32) {
   423  	e.order.PutUint32(e.buf[0:4], x)
   424  	e.buf = e.buf[4:]
   425  }
   426  
   427  func (d *decoder) uint64() uint64 {
   428  	x := d.order.Uint64(d.buf[0:8])
   429  	d.buf = d.buf[8:]
   430  	return x
   431  }
   432  
   433  func (e *encoder) uint64(x uint64) {
   434  	e.order.PutUint64(e.buf[0:8], x)
   435  	e.buf = e.buf[8:]
   436  }
   437  
   438  func (d *decoder) int8() int8 { return int8(d.uint8()) }
   439  
   440  func (e *encoder) int8(x int8) { e.uint8(uint8(x)) }
   441  
   442  func (d *decoder) int16() int16 { return int16(d.uint16()) }
   443  
   444  func (e *encoder) int16(x int16) { e.uint16(uint16(x)) }
   445  
   446  func (d *decoder) int32() int32 { return int32(d.uint32()) }
   447  
   448  func (e *encoder) int32(x int32) { e.uint32(uint32(x)) }
   449  
   450  func (d *decoder) int64() int64 { return int64(d.uint64()) }
   451  
   452  func (e *encoder) int64(x int64) { e.uint64(uint64(x)) }
   453  
   454  func (d *decoder) value(v reflect.Value) {
   455  	switch v.Kind() {
   456  	case reflect.Array:
   457  		l := v.Len()
   458  		for i := 0; i < l; i++ {
   459  			d.value(v.Index(i))
   460  		}
   461  
   462  	case reflect.Struct:
   463  		t := v.Type()
   464  		l := v.NumField()
   465  		for i := 0; i < l; i++ {
   466  			// Note: Calling v.CanSet() below is an optimization.
   467  			// It would be sufficient to check the field name,
   468  			// but creating the StructField info for each field is
   469  			// costly (run "go test -bench=ReadStruct" and compare
   470  			// results when making changes to this code).
   471  			if v := v.Field(i); v.CanSet() || t.Field(i).Name != "_" {
   472  				d.value(v)
   473  			} else {
   474  				d.skip(v)
   475  			}
   476  		}
   477  
   478  	case reflect.Slice:
   479  		l := v.Len()
   480  		for i := 0; i < l; i++ {
   481  			d.value(v.Index(i))
   482  		}
   483  
   484  	case reflect.Int8:
   485  		v.SetInt(int64(d.int8()))
   486  	case reflect.Int16:
   487  		v.SetInt(int64(d.int16()))
   488  	case reflect.Int32:
   489  		v.SetInt(int64(d.int32()))
   490  	case reflect.Int64:
   491  		v.SetInt(d.int64())
   492  
   493  	case reflect.Uint8:
   494  		v.SetUint(uint64(d.uint8()))
   495  	case reflect.Uint16:
   496  		v.SetUint(uint64(d.uint16()))
   497  	case reflect.Uint32:
   498  		v.SetUint(uint64(d.uint32()))
   499  	case reflect.Uint64:
   500  		v.SetUint(d.uint64())
   501  
   502  	case reflect.Float32:
   503  		v.SetFloat(float64(math.Float32frombits(d.uint32())))
   504  	case reflect.Float64:
   505  		v.SetFloat(math.Float64frombits(d.uint64()))
   506  
   507  	case reflect.Complex64:
   508  		v.SetComplex(complex(
   509  			float64(math.Float32frombits(d.uint32())),
   510  			float64(math.Float32frombits(d.uint32())),
   511  		))
   512  	case reflect.Complex128:
   513  		v.SetComplex(complex(
   514  			math.Float64frombits(d.uint64()),
   515  			math.Float64frombits(d.uint64()),
   516  		))
   517  	}
   518  }
   519  
   520  func (e *encoder) value(v reflect.Value) {
   521  	switch v.Kind() {
   522  	case reflect.Array:
   523  		l := v.Len()
   524  		for i := 0; i < l; i++ {
   525  			e.value(v.Index(i))
   526  		}
   527  
   528  	case reflect.Struct:
   529  		t := v.Type()
   530  		l := v.NumField()
   531  		for i := 0; i < l; i++ {
   532  			// see comment for corresponding code in decoder.value()
   533  			if v := v.Field(i); v.CanSet() || t.Field(i).Name != "_" {
   534  				e.value(v)
   535  			} else {
   536  				e.skip(v)
   537  			}
   538  		}
   539  
   540  	case reflect.Slice:
   541  		l := v.Len()
   542  		for i := 0; i < l; i++ {
   543  			e.value(v.Index(i))
   544  		}
   545  
   546  	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
   547  		switch v.Type().Kind() {
   548  		case reflect.Int8:
   549  			e.int8(int8(v.Int()))
   550  		case reflect.Int16:
   551  			e.int16(int16(v.Int()))
   552  		case reflect.Int32:
   553  			e.int32(int32(v.Int()))
   554  		case reflect.Int64:
   555  			e.int64(v.Int())
   556  		}
   557  
   558  	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
   559  		switch v.Type().Kind() {
   560  		case reflect.Uint8:
   561  			e.uint8(uint8(v.Uint()))
   562  		case reflect.Uint16:
   563  			e.uint16(uint16(v.Uint()))
   564  		case reflect.Uint32:
   565  			e.uint32(uint32(v.Uint()))
   566  		case reflect.Uint64:
   567  			e.uint64(v.Uint())
   568  		}
   569  
   570  	case reflect.Float32, reflect.Float64:
   571  		switch v.Type().Kind() {
   572  		case reflect.Float32:
   573  			e.uint32(math.Float32bits(float32(v.Float())))
   574  		case reflect.Float64:
   575  			e.uint64(math.Float64bits(v.Float()))
   576  		}
   577  
   578  	case reflect.Complex64, reflect.Complex128:
   579  		switch v.Type().Kind() {
   580  		case reflect.Complex64:
   581  			x := v.Complex()
   582  			e.uint32(math.Float32bits(float32(real(x))))
   583  			e.uint32(math.Float32bits(float32(imag(x))))
   584  		case reflect.Complex128:
   585  			x := v.Complex()
   586  			e.uint64(math.Float64bits(real(x)))
   587  			e.uint64(math.Float64bits(imag(x)))
   588  		}
   589  	}
   590  }
   591  
   592  func (d *decoder) skip(v reflect.Value) {
   593  	d.buf = d.buf[dataSize(v):]
   594  }
   595  
   596  func (e *encoder) skip(v reflect.Value) {
   597  	n := dataSize(v)
   598  	for i := range e.buf[0:n] {
   599  		e.buf[i] = 0
   600  	}
   601  	e.buf = e.buf[n:]
   602  }
   603  
   604  // intDataSize returns the size of the data required to represent the data when encoded.
   605  // It returns zero if the type cannot be implemented by the fast path in Read or Write.
   606  func intDataSize(data interface{}) int {
   607  	switch data := data.(type) {
   608  	case int8, *int8, *uint8:
   609  		return 1
   610  	case []int8:
   611  		return len(data)
   612  	case []uint8:
   613  		return len(data)
   614  	case int16, *int16, *uint16:
   615  		return 2
   616  	case []int16:
   617  		return 2 * len(data)
   618  	case []uint16:
   619  		return 2 * len(data)
   620  	case int32, *int32, *uint32:
   621  		return 4
   622  	case []int32:
   623  		return 4 * len(data)
   624  	case []uint32:
   625  		return 4 * len(data)
   626  	case int64, *int64, *uint64:
   627  		return 8
   628  	case []int64:
   629  		return 8 * len(data)
   630  	case []uint64:
   631  		return 8 * len(data)
   632  	}
   633  	return 0
   634  }
   635
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