github.com/ylsgit/go-ethereum@v1.6.5/whisper/whisperv5/doc.go (about)

     1  // Copyright 2016 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  /*
    18  Package whisper implements the Whisper protocol (version 5).
    19  
    20  Whisper combines aspects of both DHTs and datagram messaging systems (e.g. UDP).
    21  As such it may be likened and compared to both, not dissimilar to the
    22  matter/energy duality (apologies to physicists for the blatant abuse of a
    23  fundamental and beautiful natural principle).
    24  
    25  Whisper is a pure identity-based messaging system. Whisper provides a low-level
    26  (non-application-specific) but easily-accessible API without being based upon
    27  or prejudiced by the low-level hardware attributes and characteristics,
    28  particularly the notion of singular endpoints.
    29  */
    30  package whisperv5
    31  
    32  import (
    33  	"fmt"
    34  	"time"
    35  )
    36  
    37  const (
    38  	EnvelopeVersion    = uint64(0)
    39  	ProtocolVersion    = uint64(5)
    40  	ProtocolVersionStr = "5.0"
    41  	ProtocolName       = "shh"
    42  
    43  	statusCode           = 0 // used by whisper protocol
    44  	messagesCode         = 1 // normal whisper message
    45  	p2pCode              = 2 // peer-to-peer message (to be consumed by the peer, but not forwarded any further)
    46  	p2pRequestCode       = 3 // peer-to-peer message, used by Dapp protocol
    47  	NumberOfMessageCodes = 64
    48  
    49  	paddingMask   = byte(3)
    50  	signatureFlag = byte(4)
    51  
    52  	TopicLength     = 4
    53  	signatureLength = 65
    54  	aesKeyLength    = 32
    55  	AESNonceLength  = 12
    56  	keyIdSize       = 32
    57  
    58  	DefaultMaxMessageLength = 1024 * 1024
    59  	DefaultMinimumPoW       = 0.2
    60  
    61  	padSizeLimit      = 256 // just an arbitrary number, could be changed without breaking the protocol (must not exceed 2^24)
    62  	messageQueueLimit = 1024
    63  
    64  	expirationCycle   = time.Second
    65  	transmissionCycle = 300 * time.Millisecond
    66  
    67  	DefaultTTL     = 50 // seconds
    68  	SynchAllowance = 10 // seconds
    69  )
    70  
    71  type unknownVersionError uint64
    72  
    73  func (e unknownVersionError) Error() string {
    74  	return fmt.Sprintf("invalid envelope version %d", uint64(e))
    75  }
    76  
    77  // MailServer represents a mail server, capable of
    78  // archiving the old messages for subsequent delivery
    79  // to the peers. Any implementation must ensure that both
    80  // functions are thread-safe. Also, they must return ASAP.
    81  // DeliverMail should use directMessagesCode for delivery,
    82  // in order to bypass the expiry checks.
    83  type MailServer interface {
    84  	Archive(env *Envelope)
    85  	DeliverMail(whisperPeer *Peer, request *Envelope)
    86  }