README
¶
levelqueue
Level queue is a simple queue golang library base on go-leveldb.
Installation
go get gitea.com/lunny/levelqueue
Usage
queue, err := levelqueue.Open("./queue")
err = queue.RPush([]byte("test"))
// pop an element from left of the queue
data, err = queue.LPop()
// if handle success, element will be pop, otherwise it will be keep
queue.LHandle(func(dt []byte) error{
return nil
})
You can now create a Set from a leveldb:
set, err := levelqueue.OpenSet("./set")
added, err:= set.Add([]byte("member1"))
has, err := set.Has([]byte("member1"))
members, err := set.Members()
removed, err := set.Remove([]byte("member1"))
And you can create a UniqueQueue from a leveldb:
queue, err := levelqueue.OpenUnique("./queue")
err := queue.RPush([]byte("member1"))
err = queue.LPush([]byte("member1"))
// Will return ErrAlreadyInQueue
// and so on.
Creating Queues, UniqueQueues and Sets from already open DB
If you have an already open DB you can create these from this using the
NewQueue, NewUniqueQueue and NewSet functions.
Documentation
¶
Index ¶
- Variables
- type Queue
- func (queue *Queue) Close() error
- func (queue *Queue) LHandle(h func([]byte) error) error
- func (queue *Queue) LPop() ([]byte, error)
- func (queue *Queue) LPush(data []byte) error
- func (queue *Queue) Len() int64
- func (queue *Queue) RHandle(h func([]byte) error) error
- func (queue *Queue) RPop() ([]byte, error)
- func (queue *Queue) RPush(data []byte) error
- type Set
- type UniqueQueue
- func (queue *UniqueQueue) Close() error
- func (queue *UniqueQueue) Has(data []byte) (bool, error)
- func (queue *UniqueQueue) LHandle(h func([]byte) error) error
- func (queue *UniqueQueue) LPop() ([]byte, error)
- func (queue *UniqueQueue) LPush(data []byte) error
- func (queue *UniqueQueue) LPushFunc(data []byte, fn func() error) error
- func (queue *UniqueQueue) Len() int64
- func (queue *UniqueQueue) RHandle(h func([]byte) error) error
- func (queue *UniqueQueue) RPop() ([]byte, error)
- func (queue *UniqueQueue) RPush(data []byte) error
- func (queue *UniqueQueue) RPushFunc(data []byte, fn func() error) error
Constants ¶
This section is empty.
Variables ¶
var ( // ErrNotFound means no elements in queue ErrNotFound = errors.New("no key found") ErrAlreadyInQueue = errors.New("value already in queue") )
Functions ¶
This section is empty.
Types ¶
type Queue ¶
type Queue struct {
// contains filtered or unexported fields
}
Queue defines a queue struct
func NewQueue ¶ added in v0.2.0
NewQueue creates a queue from a db. The keys will be prefixed with prefix and at close the db will be closed as per closeUnderlyingDB
func Open ¶
Open opens a queue from the db path or creates a queue if it doesn't exist. The keys will not be prefixed by default
func (*Queue) LHandle ¶
LHandle receives a user callback function to handle the left element of the queue, if function return nil, then delete the element, otherwise keep the element.
type Set ¶ added in v0.2.0
type Set struct {
// contains filtered or unexported fields
}
Set defines a set struct
func NewSet ¶ added in v0.2.0
NewSet creates a set from a db. The keys will be prefixed with prefix and at close the db will be closed as per closeUnderlyingDB
func OpenSet ¶ added in v0.2.0
OpenSet opens a set from the db path or creates a set if it doesn't exist. The keys will be prefixed with "set-" by default
func (*Set) Add ¶ added in v0.2.0
Add adds a member string to a key set, returns true if the member was not already present
func (*Set) Close ¶ added in v0.2.0
Close closes the set (and the underlying db if set to closeUnderlyingDB)
type UniqueQueue ¶ added in v0.2.0
type UniqueQueue struct {
// contains filtered or unexported fields
}
UniqueQueue defines an unique queue struct
func NewUniqueQueue ¶ added in v0.2.0
func NewUniqueQueue(db *leveldb.DB, queuePrefix []byte, setPrefix []byte, closeUnderlyingDB bool) (*UniqueQueue, error)
NewUniqueQueue creates a new unique queue from a db. The queue keys will be prefixed with queuePrefix and the set keys with setPrefix and at close the db will be closed as per closeUnderlyingDB
func OpenUnique ¶ added in v0.2.0
func OpenUnique(dataDir string) (*UniqueQueue, error)
OpenUnique opens an unique queue from the db path or creates a set if it doesn't exist. The keys in the queue portion will not be prefixed, and the set keys will be prefixed with "set-"
func (*UniqueQueue) Close ¶ added in v0.2.0
func (queue *UniqueQueue) Close() error
Close closes the queue (and the underlying DB if set to closeUnderlyingDB)
func (*UniqueQueue) Has ¶ added in v0.2.0
func (queue *UniqueQueue) Has(data []byte) (bool, error)
Has checks whether the data is already in the queue
func (*UniqueQueue) LHandle ¶ added in v0.2.0
func (queue *UniqueQueue) LHandle(h func([]byte) error) error
LHandle receives a user callback function to handle the left element of the queue, if the function returns nil, then delete the element, otherwise keep the element.
func (*UniqueQueue) LPop ¶ added in v0.2.0
func (queue *UniqueQueue) LPop() ([]byte, error)
LPop pops data from left of the queue
func (*UniqueQueue) LPush ¶ added in v0.2.0
func (queue *UniqueQueue) LPush(data []byte) error
LPush pushes data to the left of the queue
func (*UniqueQueue) LPushFunc ¶ added in v0.2.0
func (queue *UniqueQueue) LPushFunc(data []byte, fn func() error) error
LPushFunc pushes data to the left of the queue and calls the callback if it is added
func (*UniqueQueue) Len ¶ added in v0.2.0
func (queue *UniqueQueue) Len() int64
Len returns the length of the queue
func (*UniqueQueue) RHandle ¶ added in v0.2.0
func (queue *UniqueQueue) RHandle(h func([]byte) error) error
RHandle receives a user callback function to handle the right element of the queue, if the function returns nil, then delete the element, otherwise keep the element.
func (*UniqueQueue) RPop ¶ added in v0.2.0
func (queue *UniqueQueue) RPop() ([]byte, error)
RPop pop data from the right of the queue
func (*UniqueQueue) RPush ¶ added in v0.2.0
func (queue *UniqueQueue) RPush(data []byte) error
RPush pushes data to the right of the queue
Source Files