github.com/palcoin-project/palcd@v1.0.0/blockchain/notifications.go (about)

     1  // Copyright (c) 2013-2016 The btcsuite developers
     2  // Use of this source code is governed by an ISC
     3  // license that can be found in the LICENSE file.
     4  
     5  package blockchain
     6  
     7  import (
     8  	"fmt"
     9  )
    10  
    11  // NotificationType represents the type of a notification message.
    12  type NotificationType int
    13  
    14  // NotificationCallback is used for a caller to provide a callback for
    15  // notifications about various chain events.
    16  type NotificationCallback func(*Notification)
    17  
    18  // Constants for the type of a notification message.
    19  const (
    20  	// NTBlockAccepted indicates the associated block was accepted into
    21  	// the block chain.  Note that this does not necessarily mean it was
    22  	// added to the main chain.  For that, use NTBlockConnected.
    23  	NTBlockAccepted NotificationType = iota
    24  
    25  	// NTBlockConnected indicates the associated block was connected to the
    26  	// main chain.
    27  	NTBlockConnected
    28  
    29  	// NTBlockDisconnected indicates the associated block was disconnected
    30  	// from the main chain.
    31  	NTBlockDisconnected
    32  )
    33  
    34  // notificationTypeStrings is a map of notification types back to their constant
    35  // names for pretty printing.
    36  var notificationTypeStrings = map[NotificationType]string{
    37  	NTBlockAccepted:     "NTBlockAccepted",
    38  	NTBlockConnected:    "NTBlockConnected",
    39  	NTBlockDisconnected: "NTBlockDisconnected",
    40  }
    41  
    42  // String returns the NotificationType in human-readable form.
    43  func (n NotificationType) String() string {
    44  	if s, ok := notificationTypeStrings[n]; ok {
    45  		return s
    46  	}
    47  	return fmt.Sprintf("Unknown Notification Type (%d)", int(n))
    48  }
    49  
    50  // Notification defines notification that is sent to the caller via the callback
    51  // function provided during the call to New and consists of a notification type
    52  // as well as associated data that depends on the type as follows:
    53  // 	- NTBlockAccepted:     *palcutil.Block
    54  // 	- NTBlockConnected:    *palcutil.Block
    55  // 	- NTBlockDisconnected: *palcutil.Block
    56  type Notification struct {
    57  	Type NotificationType
    58  	Data interface{}
    59  }
    60  
    61  // Subscribe to block chain notifications. Registers a callback to be executed
    62  // when various events take place. See the documentation on Notification and
    63  // NotificationType for details on the types and contents of notifications.
    64  func (b *BlockChain) Subscribe(callback NotificationCallback) {
    65  	b.notificationsLock.Lock()
    66  	b.notifications = append(b.notifications, callback)
    67  	b.notificationsLock.Unlock()
    68  }
    69  
    70  // sendNotification sends a notification with the passed type and data if the
    71  // caller requested notifications by providing a callback function in the call
    72  // to New.
    73  func (b *BlockChain) sendNotification(typ NotificationType, data interface{}) {
    74  	// Generate and send the notification.
    75  	n := Notification{Type: typ, Data: data}
    76  	b.notificationsLock.RLock()
    77  	for _, callback := range b.notifications {
    78  		callback(&n)
    79  	}
    80  	b.notificationsLock.RUnlock()
    81  }