github.com/xxRanger/go-ethereum@v1.8.23/swarm/storage/feed/update.go (about)

     1  // Copyright 2018 The go-ethereum Authors
     2  // This file is part of the go-ethereum library.
     3  //
     4  // The go-ethereum library is free software: you can redistribute it and/or modify
     5  // it under the terms of the GNU Lesser General Public License as published by
     6  // the Free Software Foundation, either version 3 of the License, or
     7  // (at your option) any later version.
     8  //
     9  // The go-ethereum library is distributed in the hope that it will be useful,
    10  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    11  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    12  // GNU Lesser General Public License for more details.
    13  //
    14  // You should have received a copy of the GNU Lesser General Public License
    15  // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
    16  
    17  package feed
    18  
    19  import (
    20  	"fmt"
    21  	"strconv"
    22  
    23  	"github.com/ethereum/go-ethereum/swarm/chunk"
    24  )
    25  
    26  // ProtocolVersion defines the current version of the protocol that will be included in each update message
    27  const ProtocolVersion uint8 = 0
    28  
    29  const headerLength = 8
    30  
    31  // Header defines a update message header including a protocol version byte
    32  type Header struct {
    33  	Version uint8                   // Protocol version
    34  	Padding [headerLength - 1]uint8 // reserved for future use
    35  }
    36  
    37  // Update encapsulates the information sent as part of a feed update
    38  type Update struct {
    39  	Header Header //
    40  	ID            // Feed Update identifying information
    41  	data   []byte // actual data payload
    42  }
    43  
    44  const minimumUpdateDataLength = idLength + headerLength + 1
    45  
    46  //MaxUpdateDataLength indicates the maximum payload size for a feed update
    47  const MaxUpdateDataLength = chunk.DefaultSize - signatureLength - idLength - headerLength
    48  
    49  // binaryPut serializes the feed update information into the given slice
    50  func (r *Update) binaryPut(serializedData []byte) error {
    51  	datalength := len(r.data)
    52  	if datalength == 0 {
    53  		return NewError(ErrInvalidValue, "a feed update must contain data")
    54  	}
    55  
    56  	if datalength > MaxUpdateDataLength {
    57  		return NewErrorf(ErrInvalidValue, "feed update data is too big (length=%d). Max length=%d", datalength, MaxUpdateDataLength)
    58  	}
    59  
    60  	if len(serializedData) != r.binaryLength() {
    61  		return NewErrorf(ErrInvalidValue, "slice passed to putBinary must be of exact size. Expected %d bytes", r.binaryLength())
    62  	}
    63  
    64  	var cursor int
    65  	// serialize Header
    66  	serializedData[cursor] = r.Header.Version
    67  	copy(serializedData[cursor+1:headerLength], r.Header.Padding[:headerLength-1])
    68  	cursor += headerLength
    69  
    70  	// serialize ID
    71  	if err := r.ID.binaryPut(serializedData[cursor : cursor+idLength]); err != nil {
    72  		return err
    73  	}
    74  	cursor += idLength
    75  
    76  	// add the data
    77  	copy(serializedData[cursor:], r.data)
    78  	cursor += datalength
    79  
    80  	return nil
    81  }
    82  
    83  // binaryLength returns the expected number of bytes this structure will take to encode
    84  func (r *Update) binaryLength() int {
    85  	return idLength + headerLength + len(r.data)
    86  }
    87  
    88  // binaryGet populates this instance from the information contained in the passed byte slice
    89  func (r *Update) binaryGet(serializedData []byte) error {
    90  	if len(serializedData) < minimumUpdateDataLength {
    91  		return NewErrorf(ErrNothingToReturn, "chunk less than %d bytes cannot be a feed update chunk", minimumUpdateDataLength)
    92  	}
    93  	dataLength := len(serializedData) - idLength - headerLength
    94  	// at this point we can be satisfied that we have the correct data length to read
    95  
    96  	var cursor int
    97  
    98  	// deserialize Header
    99  	r.Header.Version = serializedData[cursor]                                      // extract the protocol version
   100  	copy(r.Header.Padding[:headerLength-1], serializedData[cursor+1:headerLength]) // extract the padding
   101  	cursor += headerLength
   102  
   103  	if err := r.ID.binaryGet(serializedData[cursor : cursor+idLength]); err != nil {
   104  		return err
   105  	}
   106  	cursor += idLength
   107  
   108  	data := serializedData[cursor : cursor+dataLength]
   109  	cursor += dataLength
   110  
   111  	// now that all checks have passed, copy data into structure
   112  	r.data = make([]byte, dataLength)
   113  	copy(r.data, data)
   114  
   115  	return nil
   116  
   117  }
   118  
   119  // FromValues deserializes this instance from a string key-value store
   120  // useful to parse query strings
   121  func (r *Update) FromValues(values Values, data []byte) error {
   122  	r.data = data
   123  	version, _ := strconv.ParseUint(values.Get("protocolVersion"), 10, 32)
   124  	r.Header.Version = uint8(version)
   125  	return r.ID.FromValues(values)
   126  }
   127  
   128  // AppendValues serializes this structure into the provided string key-value store
   129  // useful to build query strings
   130  func (r *Update) AppendValues(values Values) []byte {
   131  	r.ID.AppendValues(values)
   132  	values.Set("protocolVersion", fmt.Sprintf("%d", r.Header.Version))
   133  	return r.data
   134  }