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orderedmap.go
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orderedmap.go
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package orderedmap
import (
"bytes"
"sync"
"github.com/LPX3F8/glist"
j "github.com/json-iterator/go"
)
var _customJson = j.ConfigCompatibleWithStandardLibrary
// Filter Used to filter elements during traversal
// this method receives the position index of the element in OrderedMap, and the key-value.
// Only when the method returns true will the element be passed to the subsequent Filter and Visitor.
// The relationship between multiple Filter is 'and'.
type Filter[K comparable, V any] func(idx int, key K, val V) (want bool)
// Visitor is the method to allow user access to the elements when visit all items.
// Returning true will interrupt the traversal.
type Visitor[K comparable, V any] func(idx int, key K, val V) (skip bool)
// TravelMode used to specify the direction of traversal
type TravelMode uint
const (
Forward TravelMode = iota
Reverse
)
// OrderedMap use List[T] to ensure order
// The actual key-value pair exists in the basic map
// All operations lock objects and use read-write mutex
// to reduce lock competition.
type OrderedMap[K comparable, V any] struct {
keys *glist.List[K]
items map[K]*Item[K, V]
mu *sync.RWMutex
}
// New returns a pointer of *OrderedMap[K, V]
func New[K comparable, V any]() *OrderedMap[K, V] {
return &OrderedMap[K, V]{
keys: glist.New[K](),
items: map[K]*Item[K, V]{},
mu: new(sync.RWMutex),
}
}
// Store key-value pair
func (m *OrderedMap[K, V]) Store(k K, v V) *OrderedMap[K, V] {
m.mu.Lock()
defer m.mu.Unlock()
if _, ok := m.items[k]; !ok {
m.items[k] = newItem(k, v, m.keys.PushBack(k), m)
}
return m
}
// LoadOrStore returns the existing value for the key if present.
// Otherwise, it stores and returns the given value.
// The loaded result is true if the value was loaded, false if stored.
func (m *OrderedMap[K, V]) LoadOrStore(k K, v V) (actual V, loaded bool) {
if actual, loaded = m.Load(k); loaded {
return actual, loaded
}
m.Store(k, v)
return actual, loaded
}
// Has return key exists
func (m *OrderedMap[K, V]) Has(k K) bool {
_, ok := m.Load(k)
return ok
}
// Load returns the value stored in the map for a key,
// or zero-value if no value is present, It depends on the data type.
// The ok result indicates whether value was found in the map.
func (m *OrderedMap[K, V]) Load(k K) (V, bool) {
m.mu.RLock()
defer m.mu.RUnlock()
if val, ok := m.items[k]; ok {
return val.Value(), true
}
var v V
return v, false
}
// Delete removes key-value pair
func (m *OrderedMap[K, V]) Delete(k K) *OrderedMap[K, V] {
m.mu.Lock()
defer m.mu.Unlock()
if ele, ok := m.items[k]; ok {
m.keys.Remove(ele.elements())
delete(m.items, k)
}
return m
}
// Len return the map key size
func (m *OrderedMap[K, V]) Len() int {
m.mu.RLock()
defer m.mu.RUnlock()
return m.keys.Len()
}
// Front returns the first Item of list l or nil if the list is empty.
func (m *OrderedMap[K, V]) Front() *Item[K, V] {
m.mu.RLock()
defer m.mu.RUnlock()
if n := m.keys.Front(); n != nil {
return m.items[n.Value]
}
return nil
}
// Back returns the last Item of list l or nil if the list is empty.
func (m *OrderedMap[K, V]) Back() *Item[K, V] {
m.mu.RLock()
defer m.mu.RUnlock()
if n := m.keys.Back(); n != nil {
return m.items[n.Value]
}
return nil
}
// Slice returns the elements slice
func (m *OrderedMap[K, V]) Slice(filters ...Filter[K, V]) []V {
return m.slice(Forward, filters...)
}
// Reverse the elements in the array.
func (m *OrderedMap[K, V]) Reverse(filters ...Filter[K, V]) []V {
return m.slice(Reverse, filters...)
}
// Slice returns the elements slice
func (m *OrderedMap[K, V]) slice(mode TravelMode, filters ...Filter[K, V]) []V {
slice := make([]V, m.keys.Len())
num := 0
m.Travel(mode, func(idx int, key K, val V) bool {
slice[num] = val
num++
return false
}, filters...)
return slice[:num]
}
// TravelForward all items with visitor and filters
func (m *OrderedMap[K, V]) TravelForward(f Visitor[K, V], filters ...Filter[K, V]) {
m.Travel(Forward, f, filters...)
}
// TravelReverse all items with visitor and filters
func (m *OrderedMap[K, V]) TravelReverse(f Visitor[K, V], filters ...Filter[K, V]) {
m.Travel(Reverse, f, filters...)
}
// Travel items with custom travel mode
func (m *OrderedMap[K, V]) Travel(mode TravelMode, f Visitor[K, V], filters ...Filter[K, V]) {
m.mu.RLock()
defer m.mu.RUnlock()
var (
idx int
skip bool
drop bool
hf func() *glist.Element[K]
nf func(e *glist.Element[K]) *glist.Element[K]
item *Item[K, V]
)
if mode == Forward {
hf = m.keys.Front
nf = func(e *glist.Element[K]) *glist.Element[K] { return e.Next() }
} else {
hf = m.keys.Back
nf = func(e *glist.Element[K]) *glist.Element[K] { return e.Prev() }
}
for e := hf(); e != nil; e = nf(e) {
idx++
item = m.items[e.Value]
for _, filter := range filters {
if drop = !filter(idx-1, item.Key(), item.Value()); drop {
break
}
}
if drop {
continue
}
if skip = f(idx-1, item.Key(), item.Value()); skip {
break
}
}
}
// Range calls f sequentially for each key and value present in the map.
// If f returns false, range stops the iteration.
// Deprecated: Please replace it with the TravelForward.
func (m *OrderedMap[K, V]) Range(f func(key K, val V) bool) {
m.TravelForward(func(idx int, k K, val V) bool { return f(k, val) })
return
}
// Clear empty saved elements
func (m *OrderedMap[K, V]) Clear() *OrderedMap[K, V] {
m.mu.Lock()
defer m.mu.Unlock()
m.keys = glist.New[K]()
m.items = map[K]*Item[K, V]{}
return m
}
// MarshalJSON implement the json.Marshaler interface.
// the interface implemented by types that can marshal themselves into valid JSON.
func (m *OrderedMap[K, V]) MarshalJSON() ([]byte, error) {
var err error
var keyBytes, valBytes []byte
buf := bytes.NewBuffer(nil)
buf.WriteRune('{')
for e := m.keys.Front(); e != nil; e = e.Next() {
if keyBytes, err = _customJson.Marshal(e.Value); err != nil {
break
}
if valBytes, err = _customJson.Marshal(m.items[e.Value].Value()); err != nil {
break
}
buf.Write(keyBytes)
buf.WriteRune(':')
buf.Write(valBytes)
if e.Next() != nil {
buf.WriteRune(',')
}
}
if err != nil {
return nil, err
}
buf.WriteRune('}')
return buf.Bytes(), nil
}