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orderedmap.go |
README.md
Goland Ordered Maps
Same as regular maps, but also remembers the order in which keys were inserted, akin to Python's collections.OrderedDict
s.
It offers the following features:
- optimal runtime performance (all operations are constant time)
- optimal memory usage (only one copy of values, no unnecessary memory allocation)
- allows iterating from newest or oldest keys indifferently, without memory copy, allowing to
break
the iteration, and in time linear to the number of keys iterated over rather than the total length of the ordered map - takes and returns generic
interface{}
s - idiomatic API, akin to that of
container/list
Installation
go get -u github.com/wk8/go-ordered-map
Or use your favorite golang vendoring tool!
Supported go versions
All go versions >= 1.13 are supported. There's no reason for older versions to not also work, but they're not part of the build matrix.
Documentation
The full documentation is available on godoc.org.
Example / usage
package main
import (
"fmt"
"github.com/wk8/go-ordered-map"
)
func main() {
om := orderedmap.New()
om.Set("foo", "bar")
om.Set("bar", "baz")
om.Set("coucou", "toi")
fmt.Println(om.Get("foo")) // => bar, true
fmt.Println(om.Get("i dont exist")) // => <nil>, false
// iterating pairs from oldest to newest:
for pair := om.Oldest(); pair != nil; pair = pair.Next() {
fmt.Printf("%s => %s\n", pair.Key, pair.Value)
} // prints:
// foo => bar
// bar => baz
// coucou => toi
// iterating over the 2 newest pairs:
i := 0
for pair := om.Newest(); pair != nil; pair = pair.Prev() {
fmt.Printf("%s => %s\n", pair.Key, pair.Value)
i++
if i >= 2 {
break
}
} // prints:
// coucou => toi
// bar => baz
}
All of OrderedMap
's methods accept and return interface{}
s, so you can use any type of keys that regular map
s accept, as well pack/unpack arbitrary values, e.g.:
type myStruct struct {
payload string
}
func main() {
om := orderedmap.New()
om.Set(12, &myStruct{"foo"})
om.Set(1, &myStruct{"bar"})
value, present := om.Get(12)
if !present {
panic("should be there!")
}
fmt.Println(value.(*myStruct).payload) // => foo
for pair := om.Oldest(); pair != nil; pair = pair.Next() {
fmt.Printf("%d => %s\n", pair.Key, pair.Value.(*myStruct).payload)
} // prints:
// 12 => foo
// 1 => bar
}
Alternatives
There are several other ordered map golang implementations out there, but I believe that at the time of writing none of them offer the same functionality as this library; more specifically:
- iancoleman/orderedmap only accepts
string
keys, itsDelete
operations are linear - cevaris/ordered_map uses a channel for iterations, and leaks goroutines if the iteration is interrupted before fully traversing the map
- mantyr/iterator also uses a channel for iterations, and its
Delete
operations are linear - samdolan/go-ordered-map adds unnecessary locking (users should add their own locking instead if they need it), its
Delete
andGet
operations are linear, iterations trigger a linear memory allocation