cmap

README

concurrent map

As explained here and here, the map type in Go doesn't support concurrent reads and writes. concurrent-map provides a high-performance solution to this by sharding the map with minimal time spent waiting for locks.

usage

Import the package:

import (
	"github.com/streamrail/concurrent-map"
)

go get "github.com/streamrail/concurrent-map"

The package is now imported under the "cmap" namespace.

example

	// Create a new map.
	map := cmap.New()
	
	// Sets item within map, sets "bar" under key "foo"
	map.Set("foo", "bar")

	// Retrieve item from map.
	if tmp, ok := map.Get("foo"); ok {
		bar := tmp.(string)
	}

	// Removes item under key "foo"
	map.Remove("foo")

For more examples have a look at concurrent_map_test.go.

Running tests:

go test "github.com/streamrail/concurrent-map"

templating

To generate your own custom concurrent maps please use concurrent_map_template.txt, the file is a base template for type specific maps, from terminal run:

sed 's/\<KEY\>/string/g' concurrent_map_template.go | sed 's/\<VAL\>/int/g' > cmap_string_int.go

This creates a new go source file for a string:int map.

license

MIT (see LICENSE file)

Documentation

Index

• Variables
• type ConcurrentMap
  • func New() ConcurrentMap
  • func (m ConcurrentMap) Count() int
  • func (m ConcurrentMap) Get(key string) (interface{}, bool)
  • func (m ConcurrentMap) GetShard(key string) *ConcurrentMapShared
  • func (m *ConcurrentMap) Has(key string) bool
  • func (m *ConcurrentMap) IsEmpty() bool
  • func (m ConcurrentMap) Iter() <-chan Tuple
  • func (m ConcurrentMap) IterBuffered() <-chan Tuple
  • func (m ConcurrentMap) MarshalJSON() ([]byte, error)
  • func (m *ConcurrentMap) Remove(key string)
  • func (m *ConcurrentMap) Set(key string, value interface{})
  • func (m *ConcurrentMap) SetIfAbsent(key string, value interface{}) bool
• type ConcurrentMapShared
• type Tuple

Variables

var SHARD_COUNT = 32

Types

type ConcurrentMap

type ConcurrentMap []*ConcurrentMapShared

A "thread" safe map of type string:Anything. To avoid lock bottlenecks this map is dived to several (SHARD_COUNT) map shards.

func New

func New() ConcurrentMap

Creates a new concurrent map.

func (ConcurrentMap) Count

func (m ConcurrentMap) Count() int

Returns the number of elements within the map.

func (ConcurrentMap) Get

func (m ConcurrentMap) Get(key string) (interface{}, bool)

Retrieves an element from map under given key.

func (ConcurrentMap) GetShard

func (m ConcurrentMap) GetShard(key string) *ConcurrentMapShared

Returns shard under given key

func (*ConcurrentMap) Has

func (m *ConcurrentMap) Has(key string) bool

Looks up an item under specified key

func (*ConcurrentMap) IsEmpty

func (m *ConcurrentMap) IsEmpty() bool

Checks if map is empty.

func (ConcurrentMap) Iter

func (m ConcurrentMap) Iter() <-chan Tuple

Returns an iterator which could be used in a for range loop.

func (ConcurrentMap) IterBuffered

func (m ConcurrentMap) IterBuffered() <-chan Tuple

Returns a buffered iterator which could be used in a for range loop.

func (ConcurrentMap) MarshalJSON

func (m ConcurrentMap) MarshalJSON() ([]byte, error)

Reviles ConcurrentMap "private" variables to json marshal.

func (*ConcurrentMap) Remove

func (m *ConcurrentMap) Remove(key string)

Removes an element from the map.

func (*ConcurrentMap) Set

func (m *ConcurrentMap) Set(key string, value interface{})

Sets the given value under the specified key.

func (*ConcurrentMap) SetIfAbsent

func (m *ConcurrentMap) SetIfAbsent(key string, value interface{}) bool

Sets the given value under the specified key if no value was associated with it.

type ConcurrentMapShared

type ConcurrentMapShared struct {
	sync.RWMutex // Read Write mutex, guards access to internal map.
	// contains filtered or unexported fields
}

A "thread" safe string to anything map.

type Tuple

type Tuple struct {
	Key string
	Val interface{}
}

Used by the Iter & IterBuffered functions to wrap two variables together over a channel,