proto.go

     1  // Copyright 2014 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  // This file is a simple protocol buffer encoder and decoder.
     6  //
     7  // A protocol message must implement the message interface:
     8  //   decoder() []decoder
     9  //   encode(*buffer)
    10  //
    11  // The decode method returns a slice indexed by field number that gives the
    12  // function to decode that field.
    13  // The encode method encodes its receiver into the given buffer.
    14  //
    15  // The two methods are simple enough to be implemented by hand rather than
    16  // by using a protocol compiler.
    17  //
    18  // See profile.go for examples of messages implementing this interface.
    19  //
    20  // There is no support for groups, message sets, or "has" bits.
    21  
    22  package profile
    23  
    24  import (
    25  	"errors"
    26  	"fmt"
    27  )
    28  
    29  type buffer struct {
    30  	field int
    31  	typ   int
    32  	u64   uint64
    33  	data  []byte
    34  	tmp   [16]byte
    35  }
    36  
    37  type decoder func(*buffer, message) error
    38  
    39  type message interface {
    40  	decoder() []decoder
    41  	encode(*buffer)
    42  }
    43  
    44  func marshal(m message) []byte {
    45  	var b buffer
    46  	m.encode(&b)
    47  	return b.data
    48  }
    49  
    50  func encodeVarint(b *buffer, x uint64) {
    51  	for x >= 128 {
    52  		b.data = append(b.data, byte(x)|0x80)
    53  		x >>= 7
    54  	}
    55  	b.data = append(b.data, byte(x))
    56  }
    57  
    58  func encodeLength(b *buffer, tag int, len int) {
    59  	encodeVarint(b, uint64(tag)<<3|2)
    60  	encodeVarint(b, uint64(len))
    61  }
    62  
    63  func encodeUint64(b *buffer, tag int, x uint64) {
    64  	// append varint to b.data
    65  	encodeVarint(b, uint64(tag)<<3|0)
    66  	encodeVarint(b, x)
    67  }
    68  
    69  func encodeUint64s(b *buffer, tag int, x []uint64) {
    70  	if len(x) > 2 {
    71  		// Use packed encoding
    72  		n1 := len(b.data)
    73  		for _, u := range x {
    74  			encodeVarint(b, u)
    75  		}
    76  		n2 := len(b.data)
    77  		encodeLength(b, tag, n2-n1)
    78  		n3 := len(b.data)
    79  		copy(b.tmp[:], b.data[n2:n3])
    80  		copy(b.data[n1+(n3-n2):], b.data[n1:n2])
    81  		copy(b.data[n1:], b.tmp[:n3-n2])
    82  		return
    83  	}
    84  	for _, u := range x {
    85  		encodeUint64(b, tag, u)
    86  	}
    87  }
    88  
    89  func encodeUint64Opt(b *buffer, tag int, x uint64) {
    90  	if x == 0 {
    91  		return
    92  	}
    93  	encodeUint64(b, tag, x)
    94  }
    95  
    96  func encodeInt64(b *buffer, tag int, x int64) {
    97  	u := uint64(x)
    98  	encodeUint64(b, tag, u)
    99  }
   100  
   101  func encodeInt64Opt(b *buffer, tag int, x int64) {
   102  	if x == 0 {
   103  		return
   104  	}
   105  	encodeInt64(b, tag, x)
   106  }
   107  
   108  func encodeInt64s(b *buffer, tag int, x []int64) {
   109  	if len(x) > 2 {
   110  		// Use packed encoding
   111  		n1 := len(b.data)
   112  		for _, u := range x {
   113  			encodeVarint(b, uint64(u))
   114  		}
   115  		n2 := len(b.data)
   116  		encodeLength(b, tag, n2-n1)
   117  		n3 := len(b.data)
   118  		copy(b.tmp[:], b.data[n2:n3])
   119  		copy(b.data[n1+(n3-n2):], b.data[n1:n2])
   120  		copy(b.data[n1:], b.tmp[:n3-n2])
   121  		return
   122  	}
   123  	for _, u := range x {
   124  		encodeInt64(b, tag, u)
   125  	}
   126  }
   127  
   128  func encodeString(b *buffer, tag int, x string) {
   129  	encodeLength(b, tag, len(x))
   130  	b.data = append(b.data, x...)
   131  }
   132  
   133  func encodeStrings(b *buffer, tag int, x []string) {
   134  	for _, s := range x {
   135  		encodeString(b, tag, s)
   136  	}
   137  }
   138  
   139  func encodeBool(b *buffer, tag int, x bool) {
   140  	if x {
   141  		encodeUint64(b, tag, 1)
   142  	} else {
   143  		encodeUint64(b, tag, 0)
   144  	}
   145  }
   146  
   147  func encodeBoolOpt(b *buffer, tag int, x bool) {
   148  	if !x {
   149  		return
   150  	}
   151  	encodeBool(b, tag, x)
   152  }
   153  
   154  func encodeMessage(b *buffer, tag int, m message) {
   155  	n1 := len(b.data)
   156  	m.encode(b)
   157  	n2 := len(b.data)
   158  	encodeLength(b, tag, n2-n1)
   159  	n3 := len(b.data)
   160  	copy(b.tmp[:], b.data[n2:n3])
   161  	copy(b.data[n1+(n3-n2):], b.data[n1:n2])
   162  	copy(b.data[n1:], b.tmp[:n3-n2])
   163  }
   164  
   165  func unmarshal(data []byte, m message) (err error) {
   166  	b := buffer{data: data, typ: 2}
   167  	return decodeMessage(&b, m)
   168  }
   169  
   170  func le64(p []byte) uint64 {
   171  	return uint64(p[0]) | uint64(p[1])<<8 | uint64(p[2])<<16 | uint64(p[3])<<24 | uint64(p[4])<<32 | uint64(p[5])<<40 | uint64(p[6])<<48 | uint64(p[7])<<56
   172  }
   173  
   174  func le32(p []byte) uint32 {
   175  	return uint32(p[0]) | uint32(p[1])<<8 | uint32(p[2])<<16 | uint32(p[3])<<24
   176  }
   177  
   178  func decodeVarint(data []byte) (uint64, []byte, error) {
   179  	var i int
   180  	var u uint64
   181  	for i = 0; ; i++ {
   182  		if i >= 10 || i >= len(data) {
   183  			return 0, nil, errors.New("bad varint")
   184  		}
   185  		u |= uint64(data[i]&0x7F) << uint(7*i)
   186  		if data[i]&0x80 == 0 {
   187  			return u, data[i+1:], nil
   188  		}
   189  	}
   190  }
   191  
   192  func decodeField(b *buffer, data []byte) ([]byte, error) {
   193  	x, data, err := decodeVarint(data)
   194  	if err != nil {
   195  		return nil, err
   196  	}
   197  	b.field = int(x >> 3)
   198  	b.typ = int(x & 7)
   199  	b.data = nil
   200  	b.u64 = 0
   201  	switch b.typ {
   202  	case 0:
   203  		b.u64, data, err = decodeVarint(data)
   204  		if err != nil {
   205  			return nil, err
   206  		}
   207  	case 1:
   208  		if len(data) < 8 {
   209  			return nil, errors.New("not enough data")
   210  		}
   211  		b.u64 = le64(data[:8])
   212  		data = data[8:]
   213  	case 2:
   214  		var n uint64
   215  		n, data, err = decodeVarint(data)
   216  		if err != nil {
   217  			return nil, err
   218  		}
   219  		if n > uint64(len(data)) {
   220  			return nil, errors.New("too much data")
   221  		}
   222  		b.data = data[:n]
   223  		data = data[n:]
   224  	case 5:
   225  		if len(data) < 4 {
   226  			return nil, errors.New("not enough data")
   227  		}
   228  		b.u64 = uint64(le32(data[:4]))
   229  		data = data[4:]
   230  	default:
   231  		return nil, fmt.Errorf("unknown wire type: %d", b.typ)
   232  	}
   233  
   234  	return data, nil
   235  }
   236  
   237  func checkType(b *buffer, typ int) error {
   238  	if b.typ != typ {
   239  		return errors.New("type mismatch")
   240  	}
   241  	return nil
   242  }
   243  
   244  func decodeMessage(b *buffer, m message) error {
   245  	if err := checkType(b, 2); err != nil {
   246  		return err
   247  	}
   248  	dec := m.decoder()
   249  	data := b.data
   250  	for len(data) > 0 {
   251  		// pull varint field# + type
   252  		var err error
   253  		data, err = decodeField(b, data)
   254  		if err != nil {
   255  			return err
   256  		}
   257  		if b.field >= len(dec) || dec[b.field] == nil {
   258  			continue
   259  		}
   260  		if err := dec[b.field](b, m); err != nil {
   261  			return err
   262  		}
   263  	}
   264  	return nil
   265  }
   266  
   267  func decodeInt64(b *buffer, x *int64) error {
   268  	if err := checkType(b, 0); err != nil {
   269  		return err
   270  	}
   271  	*x = int64(b.u64)
   272  	return nil
   273  }
   274  
   275  func decodeInt64s(b *buffer, x *[]int64) error {
   276  	if b.typ == 2 {
   277  		// Packed encoding
   278  		data := b.data
   279  		for len(data) > 0 {
   280  			var u uint64
   281  			var err error
   282  
   283  			if u, data, err = decodeVarint(data); err != nil {
   284  				return err
   285  			}
   286  			*x = append(*x, int64(u))
   287  		}
   288  		return nil
   289  	}
   290  	var i int64
   291  	if err := decodeInt64(b, &i); err != nil {
   292  		return err
   293  	}
   294  	*x = append(*x, i)
   295  	return nil
   296  }
   297  
   298  func decodeUint64(b *buffer, x *uint64) error {
   299  	if err := checkType(b, 0); err != nil {
   300  		return err
   301  	}
   302  	*x = b.u64
   303  	return nil
   304  }
   305  
   306  func decodeUint64s(b *buffer, x *[]uint64) error {
   307  	if b.typ == 2 {
   308  		data := b.data
   309  		// Packed encoding
   310  		for len(data) > 0 {
   311  			var u uint64
   312  			var err error
   313  
   314  			if u, data, err = decodeVarint(data); err != nil {
   315  				return err
   316  			}
   317  			*x = append(*x, u)
   318  		}
   319  		return nil
   320  	}
   321  	var u uint64
   322  	if err := decodeUint64(b, &u); err != nil {
   323  		return err
   324  	}
   325  	*x = append(*x, u)
   326  	return nil
   327  }
   328  
   329  func decodeString(b *buffer, x *string) error {
   330  	if err := checkType(b, 2); err != nil {
   331  		return err
   332  	}
   333  	*x = string(b.data)
   334  	return nil
   335  }
   336  
   337  func decodeStrings(b *buffer, x *[]string) error {
   338  	var s string
   339  	if err := decodeString(b, &s); err != nil {
   340  		return err
   341  	}
   342  	*x = append(*x, s)
   343  	return nil
   344  }
   345  
   346  func decodeBool(b *buffer, x *bool) error {
   347  	if err := checkType(b, 0); err != nil {
   348  		return err
   349  	}
   350  	if int64(b.u64) == 0 {
   351  		*x = false
   352  	} else {
   353  		*x = true
   354  	}
   355  	return nil
   356  }
   357
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