feat: custom lint rule, fixed readme

## Description

Closes #11.

## Changes

### Design Decisions

## Checklist

- [ ] Tests pass
- [ ] Docs updated

Reviewed-on: #21
Co-authored-by: M.V. Hutz <git@maximhutz.me>
Co-committed-by: M.V. Hutz <git@maximhutz.me>

.gitea/ISSUE_TEMPLATE/BUG_REPORT.yml

@@ -7,20 +7,20 @@ body:
     id: context
     attributes:
       label: Context
-      description: What circumstances led to the bug?
+      placeholder: What circumstances led to the bug?
     validations:
       required: true
   - type: textarea
     id: expected-behavior
     attributes:
       label: Expected Behavior
-      description: What did you expect would happen?
+      placeholder: What did you expect would happen?
     validations:
       required: true
   - type: textarea
     id: actual-behavior
     attributes:
       label: Actual Behavior
-      description: What happened, and why was it unexpected?
+      placeholder: What happened, and why was it unexpected?
     validations:
       required: true

.gitea/ISSUE_TEMPLATE/FEATURE_REQUEST.yml

@@ -6,18 +6,10 @@ name: ✨ Feature Request
 about: Suggest an idea for this project
 title: "[FEATURE]: "
 body:
-  - type: markdown
-    attributes:
-      value: |
-        Thanks for taking the time to fill out this feature request! 🤗
-
-        Please make sure this feature request hasn't been already submitted by
-        someone by looking through other open/closed issues. 😃
   - type: dropdown
     attributes:
       multiple: false
-      label: Type of Feature
+      label: Feature Type
-      description: Select the type of feature request.
       options:
         - "✨ New Feature"
         - "📝 Documentation"
@@ -31,7 +23,7 @@ body:
     id: description
     attributes:
       label: Description
-      description: |
+      placeholder: |
         Give us a brief description of the feature or enhancement you would
         like!
     validations:
@@ -40,6 +32,6 @@ body:
     id: additional-information
     attributes:
       label: Additional Information
-      description: |
+      placeholder: |
         Give us some additional information on the feature request like proposed
         solutions, links, screenshots, etc.

.gitea/ISSUE_TEMPLATE/config.yml

@@ -1,2 +1,2 @@
 # yaml-language-server: $schema=https://www.schemastore.org/gitea-issue-config.json
-blank_issues_enabled: true
+blank_issues_enabled: false

.gitea/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,17 @@
+---
+name: "New Pull Request"
+about: "Standard PR template"
+title: ""
+ref: "main"
+---
+
+## Description
+
+## Changes
+
+### Design Decisions
+
+## Checklist
+
+- [ ] Tests pass
+- [ ] Docs updated

.gitea/workflows/ci.yml

@@ -9,10 +9,12 @@ jobs:
   check-pr-title:
     name: Check PR Title
     runs-on: ubuntu-latest
+    if: github.event_name == 'pull_request'
+    env:
+      TITLE: ${{ gitea.event.pull_request.title }}
     steps:
       - run: |
-          TITLE="${{ gitea.event.pull_request.title }}"
+          if ! echo "$TITLE" | grep -qE '^(WIP: )?(feat|fix|docs|chore|ci|test|refactor|perf|build|style|revert)(\(.+\))?(!)?: .+'; then
-          if ! echo "$TITLE" | grep -qE '^(feat|fix|docs|chore|ci|test|refactor|perf|build|style|revert)(\(.+\))?(!)?: .+'; then
             echo "::error::Pull Request title must follow conventional commits"
             exit 1
           fi

.golangci.yml

@@ -114,6 +114,9 @@ linters:
     # Reports uses of functions with replacement inside the testing package.
     - usetesting
 
+    # Reports mixed receiver types in structs/interfaces.
+    - recvcheck
+
   settings:
     revive:
       rules:

.markdownlint-cli2.jsonc

@@ -0,0 +1,14 @@
+{
+  "customRules": [".markdownlint-rules/one-sentence-per-line.mjs"],
+  "config": {
+    "default": true,
+    "heading-style": { "style": "atx" },
+    "ul-indent": { "indent": 2 },
+    "line-length": false,
+    "no-duplicate-heading": { "siblings_only": true },
+    "no-inline-html": {
+      "allowed_elements": ["br", "code", "details", "summary", "img", "picture", "source"]
+    },
+    "first-line-heading": true
+  }
+}

.markdownlint-rules/one-sentence-per-line.mjs

@@ -0,0 +1,48 @@
+// @ts-check
+
+/**
+ * @typedef {object} ErrorInfo
+ * @property {number} lineNumber
+ * @property {string} [context]
+ * @property {string} [detail]
+ * @property {[number, number]} [range]
+ */
+
+/**
+ * @typedef {object} Params
+ * @property {string[]} lines
+ */
+
+/** @typedef {(error: ErrorInfo) => void} OnError */
+
+/**
+ * @typedef {object} Rule
+ * @property {string[]} names
+ * @property {string} description
+ * @property {string[]} tags
+ * @property {(params: Params, onError: OnError) => void} function
+ */
+
+/** @type {Rule} */
+export default {
+  names: ["one-sentence-per-line"],
+  description: "Each sentence must be on its own line",
+  tags: ["sentences"],
+  function: function (params, onError) {
+    let inFence = false;
+    params.lines.forEach((line, index) => {
+      if (/^```/.test(line)) {
+        inFence = !inFence;
+        return;
+      }
+      if (inFence) return;
+      // Skip headings, blank lines, HTML, table rows
+      if (/^(#|\s*[|<]|>|\s*$)/.test(line)) return;
+      // Strip list marker before checking
+      const text = line.replace(/^\s*(?:[-*+]|\d+\.)\s+/, "");
+      if (/[.!?]\s+[A-Z]/.test(text)) {
+        onError({ lineNumber: index + 1, context: text.trim() });
+      }
+    });
+  },
+};

.markdownlint.yml

@@ -1,17 +0,0 @@
-default: true
-heading-style:
-  style: atx
-ul-indent:
-  indent: 2
-line-length: false
-no-duplicate-heading:
-  siblings_only: true
-no-inline-html:
-  allowed_elements:
-    - br
-    - details
-    - summary
-    - img
-    - picture
-    - source
-first-line-heading: true

README.md

@@ -1,3 +1,6 @@
 # <img height="30" src="assets/logo.svg" alt="Go Cuckoo, by `mvhutz`."> Go Cuckoo
 
-A hash table that uses cuckoo hashing to achieve a worst-case O(1) lookup time. Read more about it in [the package documentation](https://pkg.go.dev/git.maximhutz.com/tools/go-cuckoo).
+A hash table that uses cuckoo hashing to achieve a worst-case O(1) lookup time.
+Read more about it in [the package documentation][docs].
+
+[docs]: https://pkg.go.dev/git.maximhutz.com/tools/go-cuckoo

bucket.go

@@ -1,103 +0,0 @@
-package cuckoo
-
-type entry[K, V any] struct {
-	key   K
-	value V
-}
-
-type slot[K, V any] struct {
-	entry[K, V]
-	occupied bool
-}
-
-type bucket[K, V any] struct {
-	hash           Hash[K]
-	slots          []slot[K, V]
-	capacity, size uint64
-	compare        EqualFunc[K]
-}
-
-// location determines where in the bucket a certain key would be placed. If the
-// capacity is 0, this will panic.
-func (b bucket[K, V]) location(key K) uint64 {
-	return b.hash(key) % b.capacity
-}
-
-func (b bucket[K, V]) get(key K) (value V, found bool) {
-	if b.capacity == 0 {
-		return
-	}
-
-	slot := b.slots[b.location(key)]
-	return slot.value, slot.occupied && b.compare(slot.key, key)
-}
-
-func (b *bucket[K, V]) drop(key K) (occupied bool) {
-	if b.capacity == 0 {
-		return
-	}
-
-	slot := &b.slots[b.location(key)]
-
-	if slot.occupied && b.compare(slot.key, key) {
-		slot.occupied = false
-		b.size--
-		return true
-	}
-
-	return false
-}
-
-func (b *bucket[K, V]) resize(capacity uint64) {
-	b.slots = make([]slot[K, V], capacity)
-	b.capacity = capacity
-	b.size = 0
-}
-
-func (b bucket[K, V]) update(key K, value V) (updated bool) {
-	if b.capacity == 0 {
-		return
-	}
-
-	slot := &b.slots[b.location(key)]
-
-	if slot.occupied && b.compare(slot.key, key) {
-		slot.value = value
-		return true
-	}
-
-	return false
-}
-
-func (b *bucket[K, V]) evict(insertion entry[K, V]) (evicted entry[K, V], eviction bool) {
-	if b.capacity == 0 {
-		return insertion, true
-	}
-
-	slot := &b.slots[b.location(insertion.key)]
-
-	if !slot.occupied {
-		slot.entry = insertion
-		slot.occupied = true
-		b.size++
-		return
-	}
-
-	if b.compare(slot.key, insertion.key) {
-		slot.value = insertion.value
-		return
-	}
-
-	insertion, slot.entry = slot.entry, insertion
-	return insertion, true
-}
-
-func newBucket[K, V any](capacity uint64, hash Hash[K], compare EqualFunc[K]) bucket[K, V] {
-	return bucket[K, V]{
-		hash:     hash,
-		capacity: capacity,
-		compare:  compare,
-		size:     0,
-		slots:    make([]slot[K, V], capacity),
-	}
-}

compare.go

@@ -2,7 +2,7 @@ package cuckoo
 
 // An EqualFunc determines whethers two keys are 'equal'. Keys that are 'equal'
 // are teated as the same by the [Table]. A good EqualFunc is pure,
-// deterministic, and fast. By default, [NewTable] uses [DefaultEqualFunc].
+// deterministic, and fast. By default, [New] uses [DefaultEqualFunc].
 //
 // This function MUST NOT return true if the [Hash] digest of two keys
 // are different: the [Table] will not work.

compare_example_test.go

@@ -28,7 +28,7 @@ func ExampleEqualFunc_badEqualFunc() {
 	// Two users with the same ID are equal.
 	isEqual := func(a, b User) bool { return a.ID == b.ID }
 
-	userbase := cuckoo.NewCustomTable[User, bool](makeHash(1), makeHash(2), isEqual)
+	userbase := cuckoo.NewCustom[User, bool](makeHash(1), makeHash(2), isEqual)
 
 	(userbase.Put(User{"1", "Robert Doe"}, true))
 

cuckoo_fuzz_test.go

@@ -3,7 +3,6 @@ package cuckoo_test
 import (
 	"fmt"
 	"maps"
-	"math"
 	"os"
 	"testing"
 
@@ -30,7 +29,6 @@ type fuzzStep struct {
 type fuzzScenario struct {
 	seedA, seedB           uint32
 	capacity, growthFactor uint8
-	load                   float64
 	steps                  []fuzzStep
 }
 
@@ -48,7 +46,6 @@ func FuzzInsertLookup(f *testing.F) {
 		seedA, seedB := scenario.seedA, scenario.seedB
 		growthFactor := max(2, int(scenario.growthFactor))
 		capacity := int(scenario.capacity)
-		minimumLoad := math.Abs(math.Mod(scenario.load, 1.0))
 
 		// If they are the same number, the hashes will clash, always causing an
 		// error.
@@ -56,43 +53,37 @@ func FuzzInsertLookup(f *testing.F) {
 			t.Skip()
 		}
 
-		// If the load is too high, the hashs will not be able to allocate
+		fmt.Fprintf(os.Stderr, "seedA=%d seedB=%d capacity=%d growthFactor=%d\n",
-		// properly.
+			seedA, seedB, capacity, growthFactor)
-		if minimumLoad > 0.20 {
-			t.Skip()
-		}
 
-		fmt.Fprintf(os.Stderr, "seedA=%d seedB=%d capacity=%d growthFactor=%d minimumLoad=%f\n",
+		actual := cuckoo.NewCustom[uint32, uint32](
-			seedA, seedB, capacity, growthFactor, minimumLoad)
-
-		actual := cuckoo.NewCustomTable[uint32, uint32](
 			offsetHash(seedA),
 			offsetHash(seedB),
 			func(a, b uint32) bool { return a == b },
 			cuckoo.Capacity(capacity),
 			cuckoo.GrowthFactor(growthFactor),
-			cuckoo.MinimumLoad(minimumLoad),
 		)
 
 		expected := map[uint32]uint32{}
 
 		for _, step := range scenario.steps {
 			if step.drop {
-				err := actual.Drop(step.key)
+				ok := actual.Drop(step.key)
-				assert.NoError(err)
+				_, has := expected[step.key]
+				assert.Equal(ok, has)
 
 				delete(expected, step.key)
 
-				_, err = actual.Get(step.key)
+				_, ok = actual.Get(step.key)
-				assert.Error(err)
+				assert.False(ok)
 			} else {
 				err := actual.Put(step.key, step.value)
 				assert.NoError(err)
 
 				expected[step.key] = step.value
 
-				found, err := actual.Get(step.key)
+				found, ok := actual.Get(step.key)
-				assert.NoError(err)
+				assert.True(ok)
 				assert.Equal(step.value, found)
 			}
 

cuckoo_internal_test.go

@@ -11,7 +11,7 @@ func TestMaxEvictions(t *testing.T) {
 	assert := assert.New(t)
 
 	for i := 16; i < 116; i++ {
-		table := NewTable[int, bool](Capacity(i / 2))
+		table := New[int, bool](Capacity(i / 2))
 		expectedEvictions := 3 * math.Floor(math.Log2(float64(i)))
 
 		assert.Equal(table.maxEvictions(), int(expectedEvictions))
@@ -20,7 +20,7 @@ func TestMaxEvictions(t *testing.T) {
 
 func TestLoad(t *testing.T) {
 	assert := assert.New(t)
-	table := NewTable[int, bool](Capacity(8))
+	table := New[int, bool](Capacity(8))
 
 	for i := range 16 {
 		err := table.Put(i, true)

cuckoo_test.go

@@ -14,7 +14,7 @@ import (
 func TestNewTable(t *testing.T) {
 	assert := assert.New(t)
 
-	table := cuckoo.NewTable[int, bool]()
+	table := cuckoo.New[int, bool]()
 
 	assert.NotNil(table)
 	assert.Zero(table.Size())
@@ -23,7 +23,7 @@ func TestNewTable(t *testing.T) {
 func TestAddItem(t *testing.T) {
 	assert := assert.New(t)
 	key, value := 0, true
-	table := cuckoo.NewTable[int, bool]()
+	table := cuckoo.New[int, bool]()
 
 	err := table.Put(key, value)
 
@@ -35,7 +35,7 @@ func TestAddItem(t *testing.T) {
 func TestPutOverwrite(t *testing.T) {
 	assert := assert.New(t)
 	key, value, newValue := 0, 1, 2
-	table := cuckoo.NewTable[int, int]()
+	table := cuckoo.New[int, int]()
 	(table.Put(key, value))
 
 	err := table.Put(key, newValue)
@@ -50,7 +50,7 @@ func TestPutOverwrite(t *testing.T) {
 func TestSameHash(t *testing.T) {
 	assert := assert.New(t)
 	hash := func(int) uint64 { return 0 }
-	table := cuckoo.NewCustomTable[int, bool](hash, hash, cuckoo.DefaultEqualFunc[int])
+	table := cuckoo.NewCustom[int, bool](hash, hash, cuckoo.DefaultEqualFunc[int])
 
 	errA := table.Put(0, true)
 	errB := table.Put(1, true)
@@ -63,14 +63,14 @@ func TestSameHash(t *testing.T) {
 
 func TestStartingCapacity(t *testing.T) {
 	assert := assert.New(t)
-	table := cuckoo.NewTable[int, bool](cuckoo.Capacity(64))
+	table := cuckoo.New[int, bool](cuckoo.Capacity(64))
 
 	assert.Equal(uint64(128), table.TotalCapacity())
 }
 
 func TestResizeCapacity(t *testing.T) {
 	assert := assert.New(t)
-	table := cuckoo.NewTable[int, bool](
+	table := cuckoo.New[int, bool](
 		cuckoo.Capacity(8),
 		cuckoo.GrowthFactor(2),
 	)
@@ -85,7 +85,7 @@ func TestResizeCapacity(t *testing.T) {
 
 func TestPutMany(t *testing.T) {
 	assert := assert.New(t)
-	expected, actual := map[int]bool{}, cuckoo.NewTable[int, bool]()
+	expected, actual := map[int]bool{}, cuckoo.New[int, bool]()
 
 	for i := range 1_000 {
 		expected[i] = true
@@ -100,7 +100,7 @@ func TestPutMany(t *testing.T) {
 
 func TestGetMany(t *testing.T) {
 	assert := assert.New(t)
-	table := cuckoo.NewTable[int, bool]()
+	table := cuckoo.New[int, bool]()
 
 	for i := range 1_000 {
 		err := table.Put(i, true)
@@ -108,12 +108,12 @@ func TestGetMany(t *testing.T) {
 	}
 
 	for i := range 2_000 {
-		value, err := table.Get(i)
+		value, ok := table.Get(i)
 		if i < 1_000 {
-			assert.NoError(err)
+			assert.True(ok)
 			assert.Equal(value, true)
 		} else {
-			assert.Error(err)
+			assert.False(ok)
 		}
 	}
 }
@@ -121,12 +121,12 @@ func TestGetMany(t *testing.T) {
 func TestDropExistingItem(t *testing.T) {
 	assert := assert.New(t)
 	key, value := 0, true
-	table := cuckoo.NewTable[int, bool]()
+	table := cuckoo.New[int, bool]()
 	(table.Put(key, value))
 
-	err := table.Drop(key)
+	had := table.Drop(key)
 
-	assert.NoError(err)
+	assert.True(had)
 	assert.Equal(0, table.Size())
 	assert.False(table.Has(key))
 }
@@ -134,11 +134,11 @@ func TestDropExistingItem(t *testing.T) {
 func TestDropNoItem(t *testing.T) {
 	assert := assert.New(t)
 	key := 0
-	table := cuckoo.NewTable[int, bool]()
+	table := cuckoo.New[int, bool]()
 
-	err := table.Drop(key)
+	had := table.Drop(key)
 
-	assert.NoError(err)
+	assert.False(had)
 	assert.Equal(0, table.Size())
 	assert.False(table.Has(key))
 }
@@ -146,16 +146,15 @@ func TestDropNoItem(t *testing.T) {
 func TestDropItemCapacity(t *testing.T) {
 	assert := assert.New(t)
 	key := 0
-	table := cuckoo.NewTable[int, bool](
+	table := cuckoo.New[int, bool](
 		cuckoo.Capacity(64),
 		cuckoo.GrowthFactor(2),
 	)
 
 	startingCapacity := table.TotalCapacity()
-	err := table.Drop(key)
+	table.Drop(key)
 	endingCapacity := table.TotalCapacity()
 
-	assert.NoError(err)
 	assert.Equal(0, table.Size())
 	assert.Equal(uint64(128), startingCapacity)
 	assert.Equal(uint64(64), endingCapacity)
@@ -164,7 +163,7 @@ func TestDropItemCapacity(t *testing.T) {
 func TestPutNoCapacity(t *testing.T) {
 	assert := assert.New(t)
 	key, value := 0, true
-	table := cuckoo.NewTable[int, bool](
+	table := cuckoo.New[int, bool](
 		cuckoo.Capacity(0),
 	)
 
@@ -177,7 +176,7 @@ func TestPutNoCapacity(t *testing.T) {
 
 func TestBadHashCapacity(t *testing.T) {
 	assert := assert.New(t)
-	table := cuckoo.NewCustomTable[int, bool](
+	table := cuckoo.NewCustom[int, bool](
 		func(int) uint64 { return 0 },
 		func(int) uint64 { return 0 },
 		func(a, b int) bool { return a == b },
@@ -197,15 +196,15 @@ func TestBadHashCapacity(t *testing.T) {
 
 func TestDropResizeCapacity(t *testing.T) {
 	assert := assert.New(t)
-	table := cuckoo.NewTable[int, bool](
+	table := cuckoo.New[int, bool](
 		cuckoo.Capacity(10),
 	)
 
 	err1 := table.Put(0, true)
 	err2 := table.Put(1, true)
-	err3 := table.Drop(1)
+	table.Drop(1)
 
-	assert.NoError(errors.Join(err1, err2, err3))
+	assert.NoError(errors.Join(err1, err2))
 	assert.Equal(uint64(20), table.TotalCapacity())
 }
 
@@ -217,9 +216,7 @@ func TestNewTableBy(t *testing.T) {
 	}
 
 	assert := assert.New(t)
-	table := cuckoo.NewTableBy[User, bool](
+	table := cuckoo.NewBy[User, bool](func(u User) string { return u.id })
-		func(u User) string { return u.id },
-	)
 
 	err := table.Put(User{nil, "1", "Robert"}, true)
 

doc.go

@@ -1,9 +1,12 @@
 // Package cuckoo provides a hash table that uses cuckoo hashing to achieve
 // a worst-case O(1) lookup time.
 //
-// While a [NewTable] only supports comparable keys by default, you can create
+// While a [New] only supports comparable keys by default, you can create
-// a table with any key type using [NewCustomTable]. Custom [Hash] functions and
+// a table with any key type using [NewCustom]. Custom [Hash] functions and
 // key comparison are also supported.
 //
+// NOTE: The [Table] is a look-up structure, and not a source of truth. If
+// [ErrBadHash] occurs, the data cannot be restored.
+//
 // See more: https://en.wikipedia.org/wiki/Cuckoo_hashing
 package cuckoo

doc_example_test.go

@@ -8,25 +8,25 @@ import (
 )
 
 func Example_basic() {
-	table := cuckoo.NewTable[int, string]()
+	table := cuckoo.New[int, string]()
 
 	if err := table.Put(1, "Hello, World!"); err != nil {
 		fmt.Println("Put error:", err)
 	}
 
-	if item, err := table.Get(1); err != nil {
+	if item, ok := table.Get(1); !ok {
-		fmt.Println("Error:", err)
+		fmt.Println("Not Found 1!")
 	} else {
 		fmt.Println("Found 1:", item)
 	}
 
-	if item, err := table.Get(0); err != nil {
+	if item, ok := table.Get(0); !ok {
-		fmt.Println("Error:", err)
+		fmt.Println("Not Found 0!")
 	} else {
 		fmt.Println("Found 0:", item)
 	}
 
 	// Output:
 	// Found 1: Hello, World!
-	// Error: key '0' not found
+	// Not Found 0!
 }

settings.go

@@ -9,14 +9,20 @@ import "fmt"
 const DefaultCapacity uint64 = 16
 
 // DefaultGrowthFactor is the standard resize multiplier for a [Table]. Most
-// hash table implementations use 2.
+// implementations use 2.
 const DefaultGrowthFactor uint64 = 2
 
-// DefaultMinimumLoad is the default lowest acceptable occupancy of a [Table].
+// defaultMinimumLoad is the default lowest acceptable occupancy of a [Table].
-// The value of 5% is taken from [libcuckoo].
+// The higher the minimum load, the more likely that a [Table.Put] will not
+// succeed. The value of 5% is taken from [libcuckoo].
 //
 // [libcuckoo]: https://github.com/efficient/libcuckoo/blob/656714705a055df2b7a605eb3c71586d9da1e119/libcuckoo/cuckoohash_config.hh#L21
-const DefaultMinimumLoad float64 = 0.05
+const defaultMinimumLoad float64 = 0.05
+
+// defaultGrowthLimit is the maximum number of times a [Table] can grow in a
+// single [Table.Put], before the library infers it will lead to a stack
+// overflow. The value of '64' was chosen arbirarily.
+const defaultGrowthLimit uint64 = 64
 
 type settings struct {
 	growthFactor  uint64
@@ -25,10 +31,10 @@ type settings struct {
 }
 
 // An Option modifies the settings of a [Table]. It is used in its constructors
-// like [NewTable], for example.
+// like [New], for example.
 type Option func(*settings)
 
-// Capacity modifies the starting capacity of each bucket of the [Table]. The
+// Capacity modifies the starting capacity of each subtable of the [Table]. The
 // value must be non-negative.
 func Capacity(value int) Option {
 	if value < 0 {
@@ -38,19 +44,6 @@ func Capacity(value int) Option {
 	return func(s *settings) { s.bucketSize = uint64(value) }
 }
 
-// MinimumLoad modifies the [DefaultMinimumLoad] of the [Table]. The value must
-// be between 0.00 and 1.00.
-//
-// The higher the minimum load, the more likely that a [Table.Put] will not
-// succeed. Minimum loads above 20% are not tested.
-func MinimumLoad(value float64) Option {
-	if value < 0.00 || value > 1.00 {
-		panic(fmt.Sprintf("go-cuckoo: MinimumLoad must be between 0.00 and 1.00, got %f", value))
-	}
-
-	return func(s *settings) { s.minLoadFactor = value }
-}
-
 // GrowthFactor controls how much the capacity of the [Table] multiplies when
 // it must resize. The value must be greater than 1.
 func GrowthFactor(value int) Option {

subtable.go

@@ -0,0 +1,107 @@
+package cuckoo
+
+// An entry is a key-value pair.
+type entry[K, V any] struct {
+	key   K
+	value V
+}
+
+type slot[K, V any] struct {
+	entry[K, V]
+	occupied bool
+}
+
+type subtable[K, V any] struct {
+	hash           Hash[K]
+	slots          []slot[K, V]
+	capacity, size uint64
+	compare        EqualFunc[K]
+}
+
+// location determines where in the subtable a certain key would be placed. If
+// the capacity is 0, this will panic.
+func (t *subtable[K, V]) location(key K) uint64 {
+	return t.hash(key) % t.capacity
+}
+
+func (t *subtable[K, V]) get(key K) (value V, found bool) {
+	if t.capacity == 0 {
+		return
+	}
+
+	slot := t.slots[t.location(key)]
+	return slot.value, slot.occupied && t.compare(slot.key, key)
+}
+
+func (t *subtable[K, V]) drop(key K) (occupied bool) {
+	if t.capacity == 0 {
+		return
+	}
+
+	slot := &t.slots[t.location(key)]
+
+	if slot.occupied && t.compare(slot.key, key) {
+		slot.occupied = false
+		t.size--
+		return true
+	}
+
+	return false
+}
+
+func (t *subtable[K, V]) resized(capacity uint64) *subtable[K, V] {
+	return &subtable[K, V]{
+		slots:    make([]slot[K, V], capacity),
+		capacity: capacity,
+		hash:     t.hash,
+		compare:  t.compare,
+	}
+}
+
+func (t *subtable[K, V]) update(key K, value V) (updated bool) {
+	if t.capacity == 0 {
+		return
+	}
+
+	slot := &t.slots[t.location(key)]
+
+	if slot.occupied && t.compare(slot.key, key) {
+		slot.value = value
+		return true
+	}
+
+	return false
+}
+
+func (t *subtable[K, V]) insert(insertion entry[K, V]) (evicted entry[K, V], eviction bool) {
+	if t.capacity == 0 {
+		return insertion, true
+	}
+
+	slot := &t.slots[t.location(insertion.key)]
+
+	if !slot.occupied {
+		slot.entry = insertion
+		slot.occupied = true
+		t.size++
+		return
+	}
+
+	if t.compare(slot.key, insertion.key) {
+		slot.value = insertion.value
+		return
+	}
+
+	insertion, slot.entry = slot.entry, insertion
+	return insertion, true
+}
+
+func newSubtable[K, V any](capacity uint64, hash Hash[K], compare EqualFunc[K]) *subtable[K, V] {
+	return &subtable[K, V]{
+		hash:     hash,
+		capacity: capacity,
+		compare:  compare,
+		size:     0,
+		slots:    make([]slot[K, V], capacity),
+	}
+}

table.go

@@ -1,41 +1,50 @@
 package cuckoo
 
 import (
+	"errors"
 	"fmt"
 	"iter"
 	"math/bits"
 	"strings"
 )
 
-// A Table is hash table that uses cuckoo hashing to resolve collision. Create
+// ErrBadHash occurs when the hashes given to a [Table] cause too many key
-// one with [NewTable]. Or if you want more granularity, use [NewTableBy] or
+// collisions. Discard the old table, rebuild it from your source data, and try:
-// [NewCustomTable].
+//
+//  1. Different hash seeds. Equal seeds produce equal hash functions, which
+//     always cycle.
+//  2. A different [Hash] algorithm.
+var ErrBadHash = errors.New("bad hash")
+
+// A Table which uses cuckoo hashing to resolve collision. Create
+// one with [New]. Or if you want more granularity, use [NewBy] or
+// [NewCustom].
 type Table[K, V any] struct {
-	bucketA, bucketB bucket[K, V]
+	tableA, tableB *subtable[K, V]
 	growthFactor   uint64
 	minLoadFactor  float64
 }
 
 // TotalCapacity returns the number of slots allocated for the [Table]. To get the
 // number of slots filled, look at [Table.Size].
-func (t Table[K, V]) TotalCapacity() uint64 {
+func (t *Table[K, V]) TotalCapacity() uint64 {
-	return t.bucketA.capacity + t.bucketB.capacity
+	return t.tableA.capacity + t.tableB.capacity
 }
 
 // Size returns how many slots are filled in the [Table].
-func (t Table[K, V]) Size() int {
+func (t *Table[K, V]) Size() int {
-	return int(t.bucketA.size + t.bucketB.size)
+	return int(t.tableA.size + t.tableB.size)
 }
 
 func log2(n uint64) (m int) {
 	return max(0, bits.Len64(n)-1)
 }
 
-func (t Table[K, V]) maxEvictions() int {
+func (t *Table[K, V]) maxEvictions() int {
 	return 3 * log2(t.TotalCapacity())
 }
 
-func (t Table[K, V]) load() float64 {
+func (t *Table[K, V]) load() float64 {
 	// When there are no slots in the table, we still treat the load as 100%.
 	// Every slot in the table is full.
 	if t.TotalCapacity() == 0 {
@@ -45,116 +54,153 @@ func (t Table[K, V]) load() float64 {
 	return float64(t.Size()) / float64(t.TotalCapacity())
 }
 
-// resize clears all buckets, changes the sizes of them to a specific capacity,
+// insert attempts to put/update an entry in the table, without modifying the
-// and fills them back up again. It is a helper function for [Table.grow] and
+// size of the table. Returns a displaced entry and 'homeless = true' if an
-// [Table.shrink]; use them instead.
+// entry could not be placed after exhausting evictions.
-func (t *Table[K, V]) resize(capacity uint64) error {
+func (t *Table[K, V]) insert(entry entry[K, V]) (displaced entry[K, V], homeless bool) {
-	entries := make([]entry[K, V], 0, t.Size())
+	if t.tableA.update(entry.key, entry.value) {
+		return
+	}
+
+	if t.tableB.update(entry.key, entry.value) {
+		return
+	}
+
+	for range t.maxEvictions() {
+		if entry, homeless = t.tableA.insert(entry); !homeless {
+			return
+		}
+
+		if entry, homeless = t.tableB.insert(entry); !homeless {
+			return
+		}
+	}
+
+	return entry, true
+}
+
+// resized creates an empty copy of the table, with a new capacity for each
+// bucket.
+func (t *Table[K, V]) resized(capacity uint64) *Table[K, V] {
+	return &Table[K, V]{
+		growthFactor:  t.growthFactor,
+		minLoadFactor: t.minLoadFactor,
+		tableA:        t.tableA.resized(capacity),
+		tableB:        t.tableB.resized(capacity),
+	}
+}
+
+// resize creates a new [Table.resized] with 'capacity', inserts all items into
+// the array, and replaces the current table. It is a helper function for
+// [Table.grow] and [Table.shrink]; use them instead.
+func (t *Table[K, V]) resize(capacity uint64) bool {
+	updated := t.resized(capacity)
+
 	for k, v := range t.Entries() {
-		entries = append(entries, entry[K, V]{k, v})
+		if _, failed := updated.insert(entry[K, V]{k, v}); failed {
-	}
+			return false
-
-	t.bucketA.resize(capacity)
-	t.bucketB.resize(capacity)
-
-	for _, entry := range entries {
-		if err := t.Put(entry.key, entry.value); err != nil {
-			return err
 		}
 	}
 
-	return nil
+	*t = *updated
+	return true
 }
 
-// grow increases the table's capacity by the [Table.growthFactor]. If the
+// grow increases the table's capacity by the growth factor. If the
 // capacity is 0, it increases it to 1.
-func (t *Table[K, V]) grow() error {
+func (t *Table[K, V]) grow() bool {
 	var newCapacity uint64
 
 	if t.TotalCapacity() == 0 {
 		newCapacity = 1
 	} else {
-		newCapacity = t.bucketA.capacity * t.growthFactor
+		newCapacity = t.tableA.capacity * t.growthFactor
 	}
 
 	return t.resize(newCapacity)
 }
 
-// shrink reduces the table's capacity by the [Table.growthFactor]. It may
+// shrink reduces the table's capacity by the growth factor. It may
 // reduce it down to 0.
-func (t *Table[K, V]) shrink() error {
+func (t *Table[K, V]) shrink() bool {
-	return t.resize(t.bucketA.capacity / t.growthFactor)
+	return t.resize(t.tableA.capacity / t.growthFactor)
 }
 
-// Get fetches the value for a key in the [Table]. Returns an error if no value
+// Get fetches the value for a key in the [Table]. Matches the comma-ok pattern
-// is found.
+// of a builtin map; see [Table.Find] for plain indexing.
-func (t Table[K, V]) Get(key K) (value V, err error) {
+func (t *Table[K, V]) Get(key K) (value V, ok bool) {
-	if item, ok := t.bucketA.get(key); ok {
+	if item, ok := t.tableA.get(key); ok {
-		return item, nil
+		return item, true
 	}
 
-	if item, ok := t.bucketB.get(key); ok {
+	if item, ok := t.tableB.get(key); ok {
-		return item, nil
+		return item, true
 	}
 
-	return value, fmt.Errorf("key '%v' not found", key)
+	return
+}
+
+// Find fetches the value of a key. Matches direct indexing of a builtin map;
+// see [Table.Get] for a comma-ok pattern.
+func (t *Table[K, V]) Find(key K) (value V) {
+	value, _ = t.Get(key)
+	return
 }
 
 // Has returns true if a key has a value in the table.
-func (t Table[K, V]) Has(key K) (exists bool) {
+func (t *Table[K, V]) Has(key K) (exists bool) {
-	_, err := t.Get(key)
+	_, exists = t.Get(key)
-	return err == nil
+	return
 }
 
-// Put sets the value for a key. Returns error if its value cannot be set.
+// Put sets the value for a key. If it cannot be set, an error is returned.
 func (t *Table[K, V]) Put(key K, value V) (err error) {
-	if t.bucketA.update(key, value) {
+	var (
-		return nil
+		entry    = entry[K, V]{key, value}
+		homeless bool
+	)
+
+	for range defaultGrowthLimit {
+		if entry, homeless = t.insert(entry); !homeless {
+			return
 		}
 
-	if t.bucketB.update(key, value) {
+		// Both this and the growth limit are necessary: this catches bad hashes
-		return nil
+		// early when the table is sparse, while the latter catches cases where
+		// growing never helps.
+		if t.load() < t.minLoadFactor {
+			return fmt.Errorf("hash functions produced a cycle at load %d/%d: %w", t.Size(), t.TotalCapacity(), ErrBadHash)
 		}
 
-	entry, eviction := entry[K, V]{key, value}, false
+		// It is theoretically possible to have a table with a larger capacity
-	for range t.maxEvictions() {
+		// that is valid. But this chance is astronomically small, so we ignore
-		if entry, eviction = t.bucketA.evict(entry); !eviction {
+		// it in this implementation.
-			return nil
+		if grew := t.grow(); !grew {
+			return fmt.Errorf("could not redistribute entries into larger table: %w", ErrBadHash)
+		}
 	}
 
-		if entry, eviction = t.bucketB.evict(entry); !eviction {
+	return fmt.Errorf("could not place entry after %d resizes: %w", defaultGrowthLimit, ErrBadHash)
-			return nil
-		}
 }
 
+// Drop removes a value for a key in the table. Returns whether the key had
+// existed.
+func (t *Table[K, V]) Drop(key K) bool {
+	occupied := t.tableA.drop(key) || t.tableB.drop(key)
+
 	if t.load() < t.minLoadFactor {
-		return fmt.Errorf("bad hash: resize on load %d/%d = %f", t.Size(), t.TotalCapacity(), t.load())
+		// The error is not handled here, because table-shrinking is an internal
+		// optimization.
+		t.shrink()
 	}
 
-	if err := t.grow(); err != nil {
+	return occupied
-		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] {
+func (t *Table[K, V]) Entries() iter.Seq2[K, V] {
 	return func(yield func(K, V) bool) {
-		for _, slot := range t.bucketA.slots {
+		for _, slot := range t.tableA.slots {
 			if slot.occupied {
 				if !yield(slot.key, slot.value) {
 					return
@@ -162,7 +208,7 @@ func (t Table[K, V]) Entries() iter.Seq2[K, V] {
 			}
 		}
 
-		for _, slot := range t.bucketB.slots {
+		for _, slot := range t.tableB.slots {
 			if slot.occupied {
 				if !yield(slot.key, slot.value) {
 					return
@@ -173,8 +219,8 @@ func (t Table[K, V]) Entries() iter.Seq2[K, V] {
 }
 
 // String returns the entries of the table as a string in the format:
-// "table[k1:v1 h2:v2 ...]".
+// "table[k1:v1 k2:v2 ...]".
-func (t Table[K, V]) String() string {
+func (t *Table[K, V]) String() string {
 	var sb strings.Builder
 	sb.WriteString("table[")
 
@@ -192,13 +238,13 @@ func (t Table[K, V]) String() string {
 	return sb.String()
 }
 
-// NewCustomTable creates a [Table] with custom [Hash] and [EqualFunc]
+// NewCustom 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] {
+func NewCustom[K, V any](hashA, hashB Hash[K], compare EqualFunc[K], options ...Option) *Table[K, V] {
 	settings := &settings{
 		growthFactor:  DefaultGrowthFactor,
 		bucketSize:    DefaultCapacity,
-		minLoadFactor: DefaultMinimumLoad,
+		minLoadFactor: defaultMinimumLoad,
 	}
 
 	for _, option := range options {
@@ -208,8 +254,8 @@ func NewCustomTable[K, V any](hashA, hashB Hash[K], compare EqualFunc[K], option
 	return &Table[K, V]{
 		growthFactor:  settings.growthFactor,
 		minLoadFactor: settings.minLoadFactor,
-		bucketA:       newBucket[K, V](settings.bucketSize, hashA, compare),
+		tableA:        newSubtable[K, V](settings.bucketSize, hashA, compare),
-		bucketB:       newBucket[K, V](settings.bucketSize, hashB, compare),
+		tableB:        newSubtable[K, V](settings.bucketSize, hashB, compare),
 	}
 }
 
@@ -217,10 +263,10 @@ 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
+// NewBy 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] {
+func NewBy[K, V any, C comparable](keyFunc func(K) C, options ...Option) *Table[K, V] {
-	return NewCustomTable[K, V](
+	return NewCustom[K, V](
 		pipe(keyFunc, NewDefaultHash[C]()),
 		pipe(keyFunc, NewDefaultHash[C]()),
 		func(a, b K) bool { return keyFunc(a) == keyFunc(b) },
@@ -228,10 +274,10 @@ func NewTableBy[K, V any, C comparable](keyFunc func(K) C, options ...Option) *T
 	)
 }
 
-// NewTable creates a [Table] using the default [Hash] and [EqualFunc]. Use
+// New 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].
+// [NewBy] or [NewCustom].
-func NewTable[K comparable, V any](options ...Option) *Table[K, V] {
+func New[K comparable, V any](options ...Option) *Table[K, V] {
-	return NewCustomTable[K, V](NewDefaultHash[K](), NewDefaultHash[K](), DefaultEqualFunc[K], options...)
+	return NewCustom[K, V](NewDefaultHash[K](), NewDefaultHash[K](), DefaultEqualFunc[K], options...)
 }