mirror of
https://github.com/superseriousbusiness/gotosocial.git
synced 2024-12-11 17:40:46 +01:00
bcb80d3ff4
* [chore] bump gruf/go-store to v2 * no more boobs
349 lines
9.3 KiB
Go
349 lines
9.3 KiB
Go
// Package hashmap provides a lock-free and thread-safe HashMap.
|
|
package hashmap
|
|
|
|
import (
|
|
"bytes"
|
|
"fmt"
|
|
"reflect"
|
|
"strconv"
|
|
"sync/atomic"
|
|
"unsafe"
|
|
)
|
|
|
|
// Map implements a read optimized hash map.
|
|
type Map[Key hashable, Value any] struct {
|
|
hasher func(Key) uintptr
|
|
store atomic.Pointer[store[Key, Value]] // pointer to a map instance that gets replaced if the map resizes
|
|
linkedList *List[Key, Value] // key sorted linked list of elements
|
|
// resizing marks a resizing operation in progress.
|
|
// this is using uintptr instead of atomic.Bool to avoid using 32 bit int on 64 bit systems
|
|
resizing atomic.Uintptr
|
|
}
|
|
|
|
// New returns a new map instance.
|
|
func New[Key hashable, Value any]() *Map[Key, Value] {
|
|
return NewSized[Key, Value](defaultSize)
|
|
}
|
|
|
|
// NewSized returns a new map instance with a specific initialization size.
|
|
func NewSized[Key hashable, Value any](size uintptr) *Map[Key, Value] {
|
|
m := &Map[Key, Value]{}
|
|
m.allocate(size)
|
|
m.setDefaultHasher()
|
|
return m
|
|
}
|
|
|
|
// SetHasher sets a custom hasher.
|
|
func (m *Map[Key, Value]) SetHasher(hasher func(Key) uintptr) {
|
|
m.hasher = hasher
|
|
}
|
|
|
|
// Len returns the number of elements within the map.
|
|
func (m *Map[Key, Value]) Len() int {
|
|
return m.linkedList.Len()
|
|
}
|
|
|
|
// Get retrieves an element from the map under given hash key.
|
|
func (m *Map[Key, Value]) Get(key Key) (Value, bool) {
|
|
hash := m.hasher(key)
|
|
|
|
for element := m.store.Load().item(hash); element != nil; element = element.Next() {
|
|
if element.keyHash == hash && element.key == key {
|
|
return element.Value(), true
|
|
}
|
|
|
|
if element.keyHash > hash {
|
|
return *new(Value), false
|
|
}
|
|
}
|
|
return *new(Value), false
|
|
}
|
|
|
|
// GetOrInsert returns the existing value for the key if present.
|
|
// Otherwise, it stores and returns the given value.
|
|
// The returned bool is true if the value was loaded, false if stored.
|
|
func (m *Map[Key, Value]) GetOrInsert(key Key, value Value) (Value, bool) {
|
|
hash := m.hasher(key)
|
|
var newElement *ListElement[Key, Value]
|
|
|
|
for {
|
|
for element := m.store.Load().item(hash); element != nil; element = element.Next() {
|
|
if element.keyHash == hash && element.key == key {
|
|
actual := element.Value()
|
|
return actual, true
|
|
}
|
|
|
|
if element.keyHash > hash {
|
|
break
|
|
}
|
|
}
|
|
|
|
if newElement == nil { // allocate only once
|
|
newElement = &ListElement[Key, Value]{
|
|
key: key,
|
|
keyHash: hash,
|
|
}
|
|
newElement.value.Store(&value)
|
|
}
|
|
|
|
if m.insertElement(newElement, hash, key, value) {
|
|
return value, false
|
|
}
|
|
}
|
|
}
|
|
|
|
// FillRate returns the fill rate of the map as a percentage integer.
|
|
func (m *Map[Key, Value]) FillRate() int {
|
|
store := m.store.Load()
|
|
count := int(store.count.Load())
|
|
l := len(store.index)
|
|
return (count * 100) / l
|
|
}
|
|
|
|
// Del deletes the key from the map and returns whether the key was deleted.
|
|
func (m *Map[Key, Value]) Del(key Key) bool {
|
|
hash := m.hasher(key)
|
|
store := m.store.Load()
|
|
element := store.item(hash)
|
|
|
|
for ; element != nil; element = element.Next() {
|
|
if element.keyHash == hash && element.key == key {
|
|
m.deleteElement(element)
|
|
m.linkedList.Delete(element)
|
|
return true
|
|
}
|
|
|
|
if element.keyHash > hash {
|
|
return false
|
|
}
|
|
}
|
|
return false
|
|
}
|
|
|
|
// Insert sets the value under the specified key to the map if it does not exist yet.
|
|
// If a resizing operation is happening concurrently while calling Insert, the item might show up in the map
|
|
// after the resize operation is finished.
|
|
// Returns true if the item was inserted or false if it existed.
|
|
func (m *Map[Key, Value]) Insert(key Key, value Value) bool {
|
|
hash := m.hasher(key)
|
|
var (
|
|
existed, inserted bool
|
|
element *ListElement[Key, Value]
|
|
)
|
|
|
|
for {
|
|
store := m.store.Load()
|
|
searchStart := store.item(hash)
|
|
|
|
if !inserted { // if retrying after insert during grow, do not add to list again
|
|
element, existed, inserted = m.linkedList.Add(searchStart, hash, key, value)
|
|
if existed {
|
|
return false
|
|
}
|
|
if !inserted {
|
|
continue // a concurrent add did interfere, try again
|
|
}
|
|
}
|
|
|
|
count := store.addItem(element)
|
|
currentStore := m.store.Load()
|
|
if store != currentStore { // retry insert in case of insert during grow
|
|
continue
|
|
}
|
|
|
|
if m.isResizeNeeded(store, count) && m.resizing.CompareAndSwap(0, 1) {
|
|
go m.grow(0, true)
|
|
}
|
|
return true
|
|
}
|
|
}
|
|
|
|
// Set sets the value under the specified key to the map. An existing item for this key will be overwritten.
|
|
// If a resizing operation is happening concurrently while calling Set, the item might show up in the map
|
|
// after the resize operation is finished.
|
|
func (m *Map[Key, Value]) Set(key Key, value Value) {
|
|
hash := m.hasher(key)
|
|
|
|
for {
|
|
store := m.store.Load()
|
|
searchStart := store.item(hash)
|
|
|
|
element, added := m.linkedList.AddOrUpdate(searchStart, hash, key, value)
|
|
if !added {
|
|
continue // a concurrent add did interfere, try again
|
|
}
|
|
|
|
count := store.addItem(element)
|
|
currentStore := m.store.Load()
|
|
if store != currentStore { // retry insert in case of insert during grow
|
|
continue
|
|
}
|
|
|
|
if m.isResizeNeeded(store, count) && m.resizing.CompareAndSwap(0, 1) {
|
|
go m.grow(0, true)
|
|
}
|
|
return
|
|
}
|
|
}
|
|
|
|
// Grow resizes the map to a new size, the size gets rounded up to next power of 2.
|
|
// To double the size of the map use newSize 0.
|
|
// This function returns immediately, the resize operation is done in a goroutine.
|
|
// No resizing is done in case of another resize operation already being in progress.
|
|
func (m *Map[Key, Value]) Grow(newSize uintptr) {
|
|
if m.resizing.CompareAndSwap(0, 1) {
|
|
go m.grow(newSize, true)
|
|
}
|
|
}
|
|
|
|
// String returns the map as a string, only hashed keys are printed.
|
|
func (m *Map[Key, Value]) String() string {
|
|
buffer := bytes.NewBufferString("")
|
|
buffer.WriteRune('[')
|
|
|
|
first := m.linkedList.First()
|
|
item := first
|
|
|
|
for item != nil {
|
|
if item != first {
|
|
buffer.WriteRune(',')
|
|
}
|
|
fmt.Fprint(buffer, item.keyHash)
|
|
item = item.Next()
|
|
}
|
|
buffer.WriteRune(']')
|
|
return buffer.String()
|
|
}
|
|
|
|
// Range calls f sequentially for each key and value present in the map.
|
|
// If f returns false, range stops the iteration.
|
|
func (m *Map[Key, Value]) Range(f func(Key, Value) bool) {
|
|
item := m.linkedList.First()
|
|
|
|
for item != nil {
|
|
value := item.Value()
|
|
if !f(item.key, value) {
|
|
return
|
|
}
|
|
item = item.Next()
|
|
}
|
|
}
|
|
|
|
func (m *Map[Key, Value]) allocate(newSize uintptr) {
|
|
m.linkedList = NewList[Key, Value]()
|
|
if m.resizing.CompareAndSwap(0, 1) {
|
|
m.grow(newSize, false)
|
|
}
|
|
}
|
|
|
|
func (m *Map[Key, Value]) isResizeNeeded(store *store[Key, Value], count uintptr) bool {
|
|
l := uintptr(len(store.index)) // l can't be 0 as it gets initialized in New()
|
|
fillRate := (count * 100) / l
|
|
return fillRate > maxFillRate
|
|
}
|
|
|
|
func (m *Map[Key, Value]) insertElement(element *ListElement[Key, Value], hash uintptr, key Key, value Value) bool {
|
|
var existed, inserted bool
|
|
|
|
for {
|
|
store := m.store.Load()
|
|
searchStart := store.item(element.keyHash)
|
|
|
|
if !inserted { // if retrying after insert during grow, do not add to list again
|
|
_, existed, inserted = m.linkedList.Add(searchStart, hash, key, value)
|
|
if existed {
|
|
return false
|
|
}
|
|
|
|
if !inserted {
|
|
continue // a concurrent add did interfere, try again
|
|
}
|
|
}
|
|
|
|
count := store.addItem(element)
|
|
currentStore := m.store.Load()
|
|
if store != currentStore { // retry insert in case of insert during grow
|
|
continue
|
|
}
|
|
|
|
if m.isResizeNeeded(store, count) && m.resizing.CompareAndSwap(0, 1) {
|
|
go m.grow(0, true)
|
|
}
|
|
return true
|
|
}
|
|
}
|
|
|
|
// deleteElement deletes an element from index.
|
|
func (m *Map[Key, Value]) deleteElement(element *ListElement[Key, Value]) {
|
|
for {
|
|
store := m.store.Load()
|
|
index := element.keyHash >> store.keyShifts
|
|
ptr := (*unsafe.Pointer)(unsafe.Pointer(uintptr(store.array) + index*intSizeBytes))
|
|
|
|
next := element.Next()
|
|
if next != nil && element.keyHash>>store.keyShifts != index {
|
|
next = nil // do not set index to next item if it's not the same slice index
|
|
}
|
|
atomic.CompareAndSwapPointer(ptr, unsafe.Pointer(element), unsafe.Pointer(next))
|
|
|
|
currentStore := m.store.Load()
|
|
if store == currentStore { // check that no resize happened
|
|
break
|
|
}
|
|
}
|
|
}
|
|
|
|
func (m *Map[Key, Value]) grow(newSize uintptr, loop bool) {
|
|
defer m.resizing.CompareAndSwap(1, 0)
|
|
|
|
for {
|
|
currentStore := m.store.Load()
|
|
if newSize == 0 {
|
|
newSize = uintptr(len(currentStore.index)) << 1
|
|
} else {
|
|
newSize = roundUpPower2(newSize)
|
|
}
|
|
|
|
index := make([]*ListElement[Key, Value], newSize)
|
|
header := (*reflect.SliceHeader)(unsafe.Pointer(&index))
|
|
|
|
newStore := &store[Key, Value]{
|
|
keyShifts: strconv.IntSize - log2(newSize),
|
|
array: unsafe.Pointer(header.Data), // use address of slice data storage
|
|
index: index,
|
|
}
|
|
|
|
m.fillIndexItems(newStore) // initialize new index slice with longer keys
|
|
|
|
m.store.Store(newStore)
|
|
|
|
m.fillIndexItems(newStore) // make sure that the new index is up-to-date with the current state of the linked list
|
|
|
|
if !loop {
|
|
return
|
|
}
|
|
|
|
// check if a new resize needs to be done already
|
|
count := uintptr(m.Len())
|
|
if !m.isResizeNeeded(newStore, count) {
|
|
return
|
|
}
|
|
newSize = 0 // 0 means double the current size
|
|
}
|
|
}
|
|
|
|
func (m *Map[Key, Value]) fillIndexItems(store *store[Key, Value]) {
|
|
first := m.linkedList.First()
|
|
item := first
|
|
lastIndex := uintptr(0)
|
|
|
|
for item != nil {
|
|
index := item.keyHash >> store.keyShifts
|
|
if item == first || index != lastIndex { // store item with smallest hash key for every index
|
|
store.addItem(item)
|
|
lastIndex = index
|
|
}
|
|
item = item.Next()
|
|
}
|
|
}
|