refactor!: shorter constructors, bucket → subtable
#22
103
bucket.go
103
bucket.go
@@ -1,103 +0,0 @@
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package cuckoo
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type entry[K, V any] struct {
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key K
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value V
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}
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type slot[K, V any] struct {
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entry[K, V]
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occupied bool
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}
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type bucket[K, V any] struct {
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hash Hash[K]
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slots []slot[K, V]
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capacity, size uint64
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compare EqualFunc[K]
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}
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// location determines where in the bucket a certain key would be placed. If the
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// capacity is 0, this will panic.
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func (b bucket[K, V]) location(key K) uint64 {
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return b.hash(key) % b.capacity
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}
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func (b bucket[K, V]) get(key K) (value V, found bool) {
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if b.capacity == 0 {
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return
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}
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slot := b.slots[b.location(key)]
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return slot.value, slot.occupied && b.compare(slot.key, key)
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}
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func (b *bucket[K, V]) drop(key K) (occupied bool) {
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if b.capacity == 0 {
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return
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}
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slot := &b.slots[b.location(key)]
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if slot.occupied && b.compare(slot.key, key) {
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slot.occupied = false
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b.size--
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return true
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}
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return false
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}
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func (b *bucket[K, V]) resize(capacity uint64) {
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b.slots = make([]slot[K, V], capacity)
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b.capacity = capacity
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b.size = 0
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}
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func (b bucket[K, V]) update(key K, value V) (updated bool) {
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if b.capacity == 0 {
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return
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}
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slot := &b.slots[b.location(key)]
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if slot.occupied && b.compare(slot.key, key) {
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slot.value = value
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return true
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}
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return false
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}
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func (b *bucket[K, V]) evict(insertion entry[K, V]) (evicted entry[K, V], eviction bool) {
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if b.capacity == 0 {
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return insertion, true
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}
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slot := &b.slots[b.location(insertion.key)]
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if !slot.occupied {
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slot.entry = insertion
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slot.occupied = true
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b.size++
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return
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}
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if b.compare(slot.key, insertion.key) {
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slot.value = insertion.value
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return
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}
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insertion, slot.entry = slot.entry, insertion
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return insertion, true
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}
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func newBucket[K, V any](capacity uint64, hash Hash[K], compare EqualFunc[K]) bucket[K, V] {
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return bucket[K, V]{
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hash: hash,
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capacity: capacity,
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compare: compare,
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size: 0,
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slots: make([]slot[K, V], capacity),
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}
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}
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237
hash_table.go
Normal file
237
hash_table.go
Normal file
@@ -0,0 +1,237 @@
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package cuckoo
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import (
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"fmt"
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"iter"
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"math/bits"
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"strings"
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)
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// A HashTable is hash table that uses cuckoo hashing to resolve collision. Create
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// one with [NewTable]. Or if you want more granularity, use [NewTableBy] or
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// [NewCustomTable].
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type HashTable[K, V any] struct {
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tableA, tableB table[K, V]
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growthFactor uint64
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minLoadFactor float64
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}
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// TotalCapacity returns the number of slots allocated for the [HashTable]. To get the
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// number of slots filled, look at [HashTable.Size].
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func (t *HashTable[K, V]) TotalCapacity() uint64 {
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return t.tableA.capacity + t.tableB.capacity
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}
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// Size returns how many slots are filled in the [HashTable].
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func (t *HashTable[K, V]) Size() int {
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return int(t.tableA.size + t.tableB.size)
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}
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func log2(n uint64) (m int) {
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return max(0, bits.Len64(n)-1)
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}
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func (t *HashTable[K, V]) maxEvictions() int {
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return 3 * log2(t.TotalCapacity())
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}
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func (t *HashTable[K, V]) load() float64 {
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// When there are no slots in the table, we still treat the load as 100%.
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// Every slot in the table is full.
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if t.TotalCapacity() == 0 {
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return 1.0
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}
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return float64(t.Size()) / float64(t.TotalCapacity())
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}
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// resize clears all buckets, changes the sizes of them to a specific capacity,
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// and fills them back up again. It is a helper function for [HashTable.grow] and
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// [HashTable.shrink]; use them instead.
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func (t *HashTable[K, V]) resize(capacity uint64) error {
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entries := make([]entry[K, V], 0, t.Size())
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for k, v := range t.Entries() {
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entries = append(entries, entry[K, V]{k, v})
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}
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t.tableA.resize(capacity)
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t.tableB.resize(capacity)
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for _, entry := range entries {
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if err := t.Put(entry.key, entry.value); err != nil {
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return err
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}
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}
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return nil
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}
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// grow increases the table's capacity by the [HashTable.growthFactor]. If the
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// capacity is 0, it increases it to 1.
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func (t *HashTable[K, V]) grow() error {
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var newCapacity uint64
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if t.TotalCapacity() == 0 {
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newCapacity = 1
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} else {
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newCapacity = t.tableA.capacity * t.growthFactor
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}
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return t.resize(newCapacity)
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}
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// shrink reduces the table's capacity by the [HashTable.growthFactor]. It may
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// reduce it down to 0.
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func (t *HashTable[K, V]) shrink() error {
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return t.resize(t.tableA.capacity / t.growthFactor)
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}
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// Get fetches the value for a key in the [HashTable]. Returns an error if no value
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// is found.
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func (t *HashTable[K, V]) Get(key K) (value V, err error) {
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if item, ok := t.tableA.get(key); ok {
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return item, nil
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}
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if item, ok := t.tableB.get(key); ok {
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return item, nil
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}
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return value, fmt.Errorf("key '%v' not found", key)
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}
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// Has returns true if a key has a value in the table.
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func (t *HashTable[K, V]) Has(key K) (exists bool) {
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_, err := t.Get(key)
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return err == nil
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}
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// Put sets the value for a key. Returns error if its value cannot be set.
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func (t *HashTable[K, V]) Put(key K, value V) (err error) {
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if t.tableA.update(key, value) {
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return nil
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}
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if t.tableB.update(key, value) {
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return nil
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}
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entry, eviction := entry[K, V]{key, value}, false
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for range t.maxEvictions() {
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if entry, eviction = t.tableA.evict(entry); !eviction {
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return nil
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}
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if entry, eviction = t.tableB.evict(entry); !eviction {
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return nil
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}
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}
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if t.load() < t.minLoadFactor {
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return fmt.Errorf("bad hash: resize on load %d/%d = %f", t.Size(), t.TotalCapacity(), t.load())
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}
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if err := t.grow(); err != nil {
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return err
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}
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return t.Put(entry.key, entry.value)
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}
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// Drop removes a value for a key in the table. Returns an error if its value
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// cannot be removed.
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func (t *HashTable[K, V]) Drop(key K) (err error) {
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t.tableA.drop(key)
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t.tableB.drop(key)
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if t.load() < t.minLoadFactor {
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return t.shrink()
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}
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return nil
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}
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// Entries returns an unordered sequence of all key-value pairs in the table.
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func (t *HashTable[K, V]) Entries() iter.Seq2[K, V] {
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return func(yield func(K, V) bool) {
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for _, slot := range t.tableA.slots {
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if slot.occupied {
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if !yield(slot.key, slot.value) {
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return
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}
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}
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}
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for _, slot := range t.tableB.slots {
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if slot.occupied {
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if !yield(slot.key, slot.value) {
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return
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}
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}
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}
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}
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}
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// String returns the entries of the table as a string in the format:
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// "table[k1:v1 h2:v2 ...]".
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func (t *HashTable[K, V]) String() string {
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var sb strings.Builder
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sb.WriteString("table[")
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first := true
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for k, v := range t.Entries() {
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if !first {
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sb.WriteString(" ")
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}
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fmt.Fprintf(&sb, "%v:%v", k, v)
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first = false
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}
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sb.WriteString("]")
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return sb.String()
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}
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// NewCustomTable creates a [HashTable] with custom [Hash] and [EqualFunc]
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// functions, along with any [Option] the user provides.
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func NewCustomTable[K, V any](hashA, hashB Hash[K], compare EqualFunc[K], options ...Option) *HashTable[K, V] {
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settings := &settings{
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growthFactor: DefaultGrowthFactor,
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bucketSize: DefaultCapacity,
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minLoadFactor: defaultMinimumLoad,
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}
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for _, option := range options {
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option(settings)
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}
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return &HashTable[K, V]{
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growthFactor: settings.growthFactor,
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minLoadFactor: settings.minLoadFactor,
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tableA: newTable[K, V](settings.bucketSize, hashA, compare),
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tableB: newTable[K, V](settings.bucketSize, hashB, compare),
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}
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}
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func pipe[X, Y, Z any](a func(X) Y, b func(Y) Z) func(X) Z {
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return func(x X) Z { return b(a(x)) }
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}
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// NewTableBy creates a [HashTable] for any key type by using keyFunc to derive a
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// comparable key. Two keys with the same derived key are treated as equal.
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func NewTableBy[K, V any, C comparable](keyFunc func(K) C, options ...Option) *HashTable[K, V] {
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return NewCustomTable[K, V](
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pipe(keyFunc, NewDefaultHash[C]()),
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pipe(keyFunc, NewDefaultHash[C]()),
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func(a, b K) bool { return keyFunc(a) == keyFunc(b) },
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options...,
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)
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}
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// NewTable creates a [HashTable] using the default [Hash] and [EqualFunc]. Use
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// the [Option] functions to configure its behavior. Note that this constructor
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// is only provided for comparable keys. For arbitrary keys, consider
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// [NewTableBy] or [NewCustomTable].
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func NewTable[K comparable, V any](options ...Option) *HashTable[K, V] {
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return NewCustomTable[K, V](NewDefaultHash[K](), NewDefaultHash[K](), DefaultEqualFunc[K], options...)
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}
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274
table.go
274
table.go
@@ -1,237 +1,103 @@
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package cuckoo
|
package cuckoo
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|
|
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import (
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type entry[K, V any] struct {
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"fmt"
|
key K
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"iter"
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value V
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"math/bits"
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"strings"
|
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)
|
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// A Table is hash table that uses cuckoo hashing to resolve collision. Create
|
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// one with [NewTable]. Or if you want more granularity, use [NewTableBy] or
|
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// [NewCustomTable].
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type Table[K, V any] struct {
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bucketA, bucketB bucket[K, V]
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growthFactor uint64
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minLoadFactor float64
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}
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}
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// TotalCapacity returns the number of slots allocated for the [Table]. To get the
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type slot[K, V any] struct {
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// number of slots filled, look at [Table.Size].
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entry[K, V]
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func (t Table[K, V]) TotalCapacity() uint64 {
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occupied bool
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return t.bucketA.capacity + t.bucketB.capacity
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}
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}
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// Size returns how many slots are filled in the [Table].
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type table[K, V any] struct {
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func (t Table[K, V]) Size() int {
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hash Hash[K]
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return int(t.bucketA.size + t.bucketB.size)
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slots []slot[K, V]
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capacity, size uint64
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compare EqualFunc[K]
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}
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}
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func log2(n uint64) (m int) {
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// location determines where in the bucket a certain key would be placed. If the
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return max(0, bits.Len64(n)-1)
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// capacity is 0, this will panic.
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func (t table[K, V]) location(key K) uint64 {
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return t.hash(key) % t.capacity
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}
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}
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func (t Table[K, V]) maxEvictions() int {
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func (t table[K, V]) get(key K) (value V, found bool) {
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return 3 * log2(t.TotalCapacity())
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if t.capacity == 0 {
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}
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return
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func (t Table[K, V]) load() float64 {
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// When there are no slots in the table, we still treat the load as 100%.
|
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// Every slot in the table is full.
|
|
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if t.TotalCapacity() == 0 {
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return 1.0
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}
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}
|
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|
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return float64(t.Size()) / float64(t.TotalCapacity())
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slot := t.slots[t.location(key)]
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return slot.value, slot.occupied && t.compare(slot.key, key)
|
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}
|
}
|
||||||
|
|
||||||
// resize clears all buckets, changes the sizes of them to a specific capacity,
|
func (t *table[K, V]) drop(key K) (occupied bool) {
|
||||||
// and fills them back up again. It is a helper function for [Table.grow] and
|
if t.capacity == 0 {
|
||||||
// [Table.shrink]; use them instead.
|
return
|
||||||
func (t *Table[K, V]) resize(capacity uint64) error {
|
|
||||||
entries := make([]entry[K, V], 0, t.Size())
|
|
||||||
for k, v := range t.Entries() {
|
|
||||||
entries = append(entries, entry[K, V]{k, v})
|
|
||||||
}
|
}
|
||||||
|
|
||||||
t.bucketA.resize(capacity)
|
slot := &t.slots[t.location(key)]
|
||||||
t.bucketB.resize(capacity)
|
|
||||||
|
|
||||||
for _, entry := range entries {
|
if slot.occupied && t.compare(slot.key, key) {
|
||||||
if err := t.Put(entry.key, entry.value); err != nil {
|
slot.occupied = false
|
||||||
return err
|
t.size--
|
||||||
}
|
return true
|
||||||
}
|
}
|
||||||
|
|
||||||
return nil
|
return false
|
||||||
}
|
}
|
||||||
|
|
||||||
// grow increases the table's capacity by the [Table.growthFactor]. If the
|
func (t *table[K, V]) resize(capacity uint64) {
|
||||||
// capacity is 0, it increases it to 1.
|
t.slots = make([]slot[K, V], capacity)
|
||||||
func (t *Table[K, V]) grow() error {
|
t.capacity = capacity
|
||||||
var newCapacity uint64
|
t.size = 0
|
||||||
|
|
||||||
if t.TotalCapacity() == 0 {
|
|
||||||
newCapacity = 1
|
|
||||||
} else {
|
|
||||||
newCapacity = t.bucketA.capacity * t.growthFactor
|
|
||||||
}
|
|
||||||
|
|
||||||
return t.resize(newCapacity)
|
|
||||||
}
|
}
|
||||||
|
|
||||||
// shrink reduces the table's capacity by the [Table.growthFactor]. It may
|
func (t table[K, V]) update(key K, value V) (updated bool) {
|
||||||
// reduce it down to 0.
|
if t.capacity == 0 {
|
||||||
func (t *Table[K, V]) shrink() error {
|
return
|
||||||
return t.resize(t.bucketA.capacity / t.growthFactor)
|
}
|
||||||
|
|
||||||
|
slot := &t.slots[t.location(key)]
|
||||||
|
|
||||||
|
if slot.occupied && t.compare(slot.key, key) {
|
||||||
|
slot.value = value
|
||||||
|
return true
|
||||||
|
}
|
||||||
|
|
||||||
|
return false
|
||||||
}
|
}
|
||||||
|
|
||||||
// Get fetches the value for a key in the [Table]. Returns an error if no value
|
func (t *table[K, V]) evict(insertion entry[K, V]) (evicted entry[K, V], eviction bool) {
|
||||||
// is found.
|
if t.capacity == 0 {
|
||||||
func (t Table[K, V]) Get(key K) (value V, err error) {
|
return insertion, true
|
||||||
if item, ok := t.bucketA.get(key); ok {
|
|
||||||
return item, nil
|
|
||||||
}
|
}
|
||||||
|
|
||||||
if item, ok := t.bucketB.get(key); ok {
|
slot := &t.slots[t.location(insertion.key)]
|
||||||
return item, nil
|
|
||||||
|
if !slot.occupied {
|
||||||
|
slot.entry = insertion
|
||||||
|
slot.occupied = true
|
||||||
|
t.size++
|
||||||
|
return
|
||||||
}
|
}
|
||||||
|
|
||||||
return value, fmt.Errorf("key '%v' not found", key)
|
if t.compare(slot.key, insertion.key) {
|
||||||
|
slot.value = insertion.value
|
||||||
|
return
|
||||||
|
}
|
||||||
|
|
||||||
|
insertion, slot.entry = slot.entry, insertion
|
||||||
|
return insertion, true
|
||||||
}
|
}
|
||||||
|
|
||||||
// Has returns true if a key has a value in the table.
|
func newTable[K, V any](capacity uint64, hash Hash[K], compare EqualFunc[K]) table[K, V] {
|
||||||
func (t Table[K, V]) Has(key K) (exists bool) {
|
return table[K, V]{
|
||||||
_, err := t.Get(key)
|
hash: hash,
|
||||||
return err == nil
|
capacity: capacity,
|
||||||
}
|
compare: compare,
|
||||||
|
size: 0,
|
||||||
// Put sets the value for a key. Returns error if its value cannot be set.
|
slots: make([]slot[K, V], capacity),
|
||||||
func (t *Table[K, V]) Put(key K, value V) (err error) {
|
|
||||||
if t.bucketA.update(key, value) {
|
|
||||||
return nil
|
|
||||||
}
|
|
||||||
|
|
||||||
if t.bucketB.update(key, value) {
|
|
||||||
return nil
|
|
||||||
}
|
|
||||||
|
|
||||||
entry, eviction := entry[K, V]{key, value}, false
|
|
||||||
for range t.maxEvictions() {
|
|
||||||
if entry, eviction = t.bucketA.evict(entry); !eviction {
|
|
||||||
return nil
|
|
||||||
}
|
|
||||||
|
|
||||||
if entry, eviction = t.bucketB.evict(entry); !eviction {
|
|
||||||
return nil
|
|
||||||
}
|
|
||||||
}
|
|
||||||
|
|
||||||
if t.load() < t.minLoadFactor {
|
|
||||||
return fmt.Errorf("bad hash: resize on load %d/%d = %f", t.Size(), t.TotalCapacity(), t.load())
|
|
||||||
}
|
|
||||||
|
|
||||||
if err := t.grow(); err != nil {
|
|
||||||
return err
|
|
||||||
}
|
|
||||||
|
|
||||||
return t.Put(entry.key, entry.value)
|
|
||||||
}
|
|
||||||
|
|
||||||
// Drop removes a value for a key in the table. Returns an error if its value
|
|
||||||
// cannot be removed.
|
|
||||||
func (t *Table[K, V]) Drop(key K) (err error) {
|
|
||||||
t.bucketA.drop(key)
|
|
||||||
t.bucketB.drop(key)
|
|
||||||
|
|
||||||
if t.load() < t.minLoadFactor {
|
|
||||||
return t.shrink()
|
|
||||||
}
|
|
||||||
|
|
||||||
return nil
|
|
||||||
}
|
|
||||||
|
|
||||||
// Entries returns an unordered sequence of all key-value pairs in the table.
|
|
||||||
func (t Table[K, V]) Entries() iter.Seq2[K, V] {
|
|
||||||
return func(yield func(K, V) bool) {
|
|
||||||
for _, slot := range t.bucketA.slots {
|
|
||||||
if slot.occupied {
|
|
||||||
if !yield(slot.key, slot.value) {
|
|
||||||
return
|
|
||||||
}
|
|
||||||
}
|
|
||||||
}
|
|
||||||
|
|
||||||
for _, slot := range t.bucketB.slots {
|
|
||||||
if slot.occupied {
|
|
||||||
if !yield(slot.key, slot.value) {
|
|
||||||
return
|
|
||||||
}
|
|
||||||
}
|
|
||||||
}
|
|
||||||
}
|
}
|
||||||
}
|
}
|
||||||
|
|
||||||
// String returns the entries of the table as a string in the format:
|
|
||||||
// "table[k1:v1 h2:v2 ...]".
|
|
||||||
func (t Table[K, V]) String() string {
|
|
||||||
var sb strings.Builder
|
|
||||||
sb.WriteString("table[")
|
|
||||||
|
|
||||||
first := true
|
|
||||||
for k, v := range t.Entries() {
|
|
||||||
if !first {
|
|
||||||
sb.WriteString(" ")
|
|
||||||
}
|
|
||||||
|
|
||||||
fmt.Fprintf(&sb, "%v:%v", k, v)
|
|
||||||
first = false
|
|
||||||
}
|
|
||||||
|
|
||||||
sb.WriteString("]")
|
|
||||||
return sb.String()
|
|
||||||
}
|
|
||||||
|
|
||||||
// NewCustomTable creates a [Table] with custom [Hash] and [EqualFunc]
|
|
||||||
// functions, along with any [Option] the user provides.
|
|
||||||
func NewCustomTable[K, V any](hashA, hashB Hash[K], compare EqualFunc[K], options ...Option) *Table[K, V] {
|
|
||||||
settings := &settings{
|
|
||||||
growthFactor: DefaultGrowthFactor,
|
|
||||||
bucketSize: DefaultCapacity,
|
|
||||||
minLoadFactor: defaultMinimumLoad,
|
|
||||||
}
|
|
||||||
|
|
||||||
for _, option := range options {
|
|
||||||
option(settings)
|
|
||||||
}
|
|
||||||
|
|
||||||
return &Table[K, V]{
|
|
||||||
growthFactor: settings.growthFactor,
|
|
||||||
minLoadFactor: settings.minLoadFactor,
|
|
||||||
bucketA: newBucket[K, V](settings.bucketSize, hashA, compare),
|
|
||||||
bucketB: newBucket[K, V](settings.bucketSize, hashB, compare),
|
|
||||||
}
|
|
||||||
}
|
|
||||||
|
|
||||||
func pipe[X, Y, Z any](a func(X) Y, b func(Y) Z) func(X) Z {
|
|
||||||
return func(x X) Z { return b(a(x)) }
|
|
||||||
}
|
|
||||||
|
|
||||||
// NewTableBy creates a [Table] for any key type by using keyFunc to derive a
|
|
||||||
// comparable key. Two keys with the same derived key are treated as equal.
|
|
||||||
func NewTableBy[K, V any, C comparable](keyFunc func(K) C, options ...Option) *Table[K, V] {
|
|
||||||
return NewCustomTable[K, V](
|
|
||||||
pipe(keyFunc, NewDefaultHash[C]()),
|
|
||||||
pipe(keyFunc, NewDefaultHash[C]()),
|
|
||||||
func(a, b K) bool { return keyFunc(a) == keyFunc(b) },
|
|
||||||
options...,
|
|
||||||
)
|
|
||||||
}
|
|
||||||
|
|
||||||
// NewTable creates a [Table] using the default [Hash] and [EqualFunc]. Use
|
|
||||||
// the [Option] functions to configure its behavior. Note that this constructor
|
|
||||||
// is only provided for comparable keys. For arbitrary keys, consider
|
|
||||||
// [NewTableBy] or [NewCustomTable].
|
|
||||||
func NewTable[K comparable, V any](options ...Option) *Table[K, V] {
|
|
||||||
return NewCustomTable[K, V](NewDefaultHash[K](), NewDefaultHash[K](), DefaultEqualFunc[K], options...)
|
|
||||||
}
|
|
||||||
|
|||||||
Reference in New Issue
Block a user