9 Commits

Author SHA1 Message Date
ca66ccd040 fix: public facing key/value fields in entry
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2026-04-04 00:38:27 +02:00
afead3330a feat: drop item returns bool, whether item existed 2026-04-04 00:20:34 +02:00
05b633afca feat: new put implementation 2026-04-04 00:13:50 +02:00
322d71f0be refactor!: remove MinimumLoad() option (#17)
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## Description

The `cuckoo.MinimumLoad()` option was not a very useful option, and prone to error. By removing the ability to modify it, and setting it to something reasonable (like 5%), we can remove a whole set of errors that the user may stumble into.

## Changes

- Remove `MinimumLoad()` option.
- Privated `DefaultMinimumLoad`.

### Design Decisions

- `DefaultMinimumLoad` should be privated because it is no longer an option. The user should not need to interact with it.

## Checklist

- [x] Tests pass
- [x] Docs updated

Reviewed-on: #17
2026-04-03 14:51:41 +00:00
ed30a4fc7c fix: check-pr-title job has prompt injection (#18)
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## Description

Currently, the `check-pr-title` job has a security vulnerability. If you give the PR a bad title, the job can run arbitrary code.

## Changes

- Fix prompt injection by pulling the PR title as an environment variable.
- Also, restricted the job to only `pull_request` trigger.

### Design Decisions

- It is better to pull out this job into a separate workflow with a unique trigger, but I chose not to because it is currently only one job.

## Checklist

- [x] Tests pass
- [x] Docs updated

Reviewed-on: #18
Co-authored-by: M.V. Hutz <git@maximhutz.me>
Co-committed-by: M.V. Hutz <git@maximhutz.me>
2026-04-03 14:47:01 +00:00
c834f004a2 chore: no free form issues, 'description'-s to 'placeholders'-s (#16)
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## Description

There were some problems with the roll-out of the issue templates. This PR addresses them.

## Changes

- Disable `blank-issue-enabled`.
- Move all `description` types in the issue templates to `placeholder`.

### Design Decisions

- The `description` fields take up too much space.

## Checklist

- [x] Tests pass
- [x] Docs updated

Reviewed-on: #16
Co-authored-by: M.V. Hutz <git@maximhutz.me>
Co-committed-by: M.V. Hutz <git@maximhutz.me>
2026-04-03 13:57:03 +00:00
581f26f562 ci: support semantic versioning, conventional commits (#15)
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## Description

Currently, the repository is not well suited for semantic versioning, and hasn't much to support it. This PR adds templates, CI jobs, and configs to simplify its adoption.

## Changes

- Added `FEATURE` and `BUG` issue templates. Also, forbids free-form issues.
- Adds a PR template.
- Adds a CI job to ensure the commit title follows conventional commits.

### Design Decisions

N/A.

## Checklist

- [x] Tests pass
- [x] Docs updated

Reviewed-on: #15
Co-authored-by: M.V. Hutz <git@maximhutz.me>
Co-committed-by: M.V. Hutz <git@maximhutz.me>
2026-04-03 13:46:05 +00:00
b1ab3a6326 chore: remove ./.claude/settings.json (#14)
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There shouldn't be a global settings folder for Claude in the repository. Also, add final newline to `.gitignore`.

Reviewed-on: #14
Co-authored-by: M.V. Hutz <git@maximhutz.me>
Co-committed-by: M.V. Hutz <git@maximhutz.me>
2026-03-28 19:52:06 +00:00
36d76d4929 feat: wider fuzz tests, stronger options. (#9)
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- Added all `Option`-s to the fuzz tests.
  - Minimum load is always <=20%.
- Tested all options, and force a panic on all invalid options.
  - Capacity must now be non-negative.
  - Minimum load should be <=20%, but just put it as a recommendation.

Reviewed-on: #9
Co-authored-by: M.V. Hutz <git@maximhutz.me>
Co-committed-by: M.V. Hutz <git@maximhutz.me>
2026-03-25 01:26:56 +00:00
17 changed files with 265 additions and 234 deletions

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@@ -1,7 +0,0 @@
{
"permissions": {
"allow": [
"Bash(curl -s -w \"\\\\n---HTTP_STATUS:%{http_code}---\" https://raw.githubusercontent.com/kubernetes/kubernetes/master/.markdownlint.yaml)"
]
}
}

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@@ -1,71 +0,0 @@
name: Bug Report
about: File a bug report
title: "[Bug]: "
body:
- type: markdown
attributes:
value: |
Thanks for taking the time to fill out this bug report!
# some markdown that will only be visible once the issue has been created
- type: markdown
attributes:
value: |
This issue was created by an issue **template** :)
visible: [content]
- type: input
id: contact
attributes:
label: Contact Details
description: How can we get in touch with you if we need more info?
placeholder: ex. email@example.com
validations:
required: false
- type: textarea
id: what-happened
attributes:
label: What happened?
description: Also tell us, what did you expect to happen?
placeholder: Tell us what you see!
value: "A bug happened!"
validations:
required: true
- type: dropdown
id: version
attributes:
label: Version
description: What version of our software are you running?
options:
- 1.0.2 (Default)
- 1.0.3 (Edge)
validations:
required: true
- type: dropdown
id: browsers
attributes:
label: What browsers are you seeing the problem on?
multiple: true
options:
- Firefox
- Chrome
- Safari
- Microsoft Edge
- type: textarea
id: logs
attributes:
label: Relevant log output
description: Please copy and paste any relevant log output. This will be automatically formatted into code, so no need for backticks.
render: shell
- type: checkboxes
id: terms
attributes:
label: Code of Conduct
hide_label: true
description: By submitting this issue, you agree to follow our [Code of Conduct](https://example.com)
options:
- label: I agree to follow this project's Code of Conduct
required: true
- label: I have also read the CONTRIBUTION.MD
required: true
visible: [form]
- label: This is a TODO only visible after issue creation
visible: [content]

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@@ -0,0 +1,26 @@
# yaml-language-server: $schema=https://www.schemastore.org/gitea-issue-forms.json
name: 🐛 Bug Report
about: Report a bug in this project
title: "[BUG]: "
body:
- type: textarea
id: context
attributes:
label: Context
placeholder: What circumstances led to the bug?
validations:
required: true
- type: textarea
id: expected-behavior
attributes:
label: Expected Behavior
placeholder: What did you expect would happen?
validations:
required: true
- type: textarea
id: actual-behavior
attributes:
label: Actual Behavior
placeholder: What happened, and why was it unexpected?
validations:
required: true

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@@ -0,0 +1,37 @@
# 'Feature Request Template' By @cheehwatang
# https://github.com/cheehwatang/.github/blob/master/.github/ISSUE_TEMPLATE/feature_request.yml
#
# yaml-language-server: $schema=https://www.schemastore.org/gitea-issue-forms.json
name: ✨ Feature Request
about: Suggest an idea for this project
title: "[FEATURE]: "
body:
- type: dropdown
attributes:
multiple: false
label: Feature Type
options:
- "✨ New Feature"
- "📝 Documentation"
- "🎨 Style and UI"
- "🔨 Code Refactor"
- "⚡ Performance Improvements"
- "✅ New Test"
validations:
required: true
- type: textarea
id: description
attributes:
label: Description
placeholder: |
Give us a brief description of the feature or enhancement you would
like!
validations:
required: true
- type: textarea
id: additional-information
attributes:
label: Additional Information
placeholder: |
Give us some additional information on the feature request like proposed
solutions, links, screenshots, etc.

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@@ -0,0 +1,2 @@
# yaml-language-server: $schema=https://www.schemastore.org/gitea-issue-config.json
blank_issues_enabled: false

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@@ -1,12 +1,17 @@
--- ---
name: "Pull Request Template" name: "New Pull Request"
about: "This template is for general pull requests!" about: "Standard PR template"
title: "<type>[optional scope]: <description>" title: ""
ref: "main" ref: "main"
assignees: ["user1"]
labels:
- bug
- "help needed"
--- ---
This is the template! ## Description
## Changes
### Design Decisions
## Checklist
- [ ] Tests pass
- [ ] Docs updated

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@@ -6,6 +6,19 @@ on:
pull_request: pull_request:
jobs: jobs:
check-pr-title:
name: Check PR Title
runs-on: ubuntu-latest
if: github.event_name == 'pull_request'
env:
TITLE: ${{ gitea.event.pull_request.title }}
steps:
- run: |
if ! echo "$TITLE" | grep -qE '^(WIP: )?(feat|fix|docs|chore|ci|test|refactor|perf|build|style|revert)(\(.+\))?(!)?: .+'; then
echo "::error::Pull Request title must follow conventional commits"
exit 1
fi
lint-go: lint-go:
name: Go Lint name: Go Lint
runs-on: ubuntu-latest runs-on: ubuntu-latest

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@@ -1,22 +0,0 @@
name: Release
on:
push:
branches: [main]
jobs:
release:
runs-on: ubuntu-latest
steps:
- uses: actions/checkout@v4
with:
fetch-depth: 0
- uses: actions/setup-python@v5
with:
python-version: "3.12"
- run: pip install python-semantic-release
- run: semantic-release version --push --vcs-release
env:
GITEA_TOKEN: ${{ secrets.GITEA_TOKEN }}

1
.gitignore vendored
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@@ -24,4 +24,3 @@ go.work.sum
# env file # env file
.env .env

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@@ -1,12 +1,13 @@
package cuckoo package cuckoo
type entry[K, V any] struct { // An Entry is a key-value pair.
key K type Entry[K, V any] struct {
value V Key K
Value V
} }
type slot[K, V any] struct { type slot[K, V any] struct {
entry[K, V] Entry[K, V]
occupied bool occupied bool
} }
@@ -29,7 +30,7 @@ func (b bucket[K, V]) get(key K) (value V, found bool) {
} }
slot := b.slots[b.location(key)] slot := b.slots[b.location(key)]
return slot.value, slot.occupied && b.compare(slot.key, key) return slot.Value, slot.occupied && b.compare(slot.Key, key)
} }
func (b *bucket[K, V]) drop(key K) (occupied bool) { func (b *bucket[K, V]) drop(key K) (occupied bool) {
@@ -39,7 +40,7 @@ func (b *bucket[K, V]) drop(key K) (occupied bool) {
slot := &b.slots[b.location(key)] slot := &b.slots[b.location(key)]
if slot.occupied && b.compare(slot.key, key) { if slot.occupied && b.compare(slot.Key, key) {
slot.occupied = false slot.occupied = false
b.size-- b.size--
return true return true
@@ -48,10 +49,13 @@ func (b *bucket[K, V]) drop(key K) (occupied bool) {
return false return false
} }
func (b *bucket[K, V]) resize(capacity uint64) { func (b *bucket[K, V]) resized(capacity uint64) bucket[K, V] {
b.slots = make([]slot[K, V], capacity) return bucket[K, V]{
b.capacity = capacity slots: make([]slot[K, V], capacity),
b.size = 0 capacity: capacity,
hash: b.hash,
compare: b.compare,
}
} }
func (b bucket[K, V]) update(key K, value V) (updated bool) { func (b bucket[K, V]) update(key K, value V) (updated bool) {
@@ -61,34 +65,34 @@ func (b bucket[K, V]) update(key K, value V) (updated bool) {
slot := &b.slots[b.location(key)] slot := &b.slots[b.location(key)]
if slot.occupied && b.compare(slot.key, key) { if slot.occupied && b.compare(slot.Key, key) {
slot.value = value slot.Value = value
return true return true
} }
return false return false
} }
func (b *bucket[K, V]) evict(insertion entry[K, V]) (evicted entry[K, V], eviction bool) { func (b *bucket[K, V]) insert(insertion Entry[K, V]) (evicted Entry[K, V], eviction bool) {
if b.capacity == 0 { if b.capacity == 0 {
return insertion, true return insertion, true
} }
slot := &b.slots[b.location(insertion.key)] slot := &b.slots[b.location(insertion.Key)]
if !slot.occupied { if !slot.occupied {
slot.entry = insertion slot.Entry = insertion
slot.occupied = true slot.occupied = true
b.size++ b.size++
return return
} }
if b.compare(slot.key, insertion.key) { if b.compare(slot.Key, insertion.Key) {
slot.value = insertion.value slot.Value = insertion.Value
return return
} }
insertion, slot.entry = slot.entry, insertion insertion, slot.Entry = slot.Entry, insertion
return insertion, true return insertion, true
} }

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@@ -1,7 +1,9 @@
package cuckoo_test package cuckoo_test
import ( import (
"fmt"
"maps" "maps"
"os"
"testing" "testing"
"github.com/stretchr/testify/assert" "github.com/stretchr/testify/assert"
@@ -25,8 +27,9 @@ type fuzzStep struct {
} }
type fuzzScenario struct { type fuzzScenario struct {
seedA, seedB uint32 seedA, seedB uint32
steps []fuzzStep capacity, growthFactor uint8
steps []fuzzStep
} }
func FuzzInsertLookup(f *testing.F) { func FuzzInsertLookup(f *testing.F) {
@@ -40,29 +43,41 @@ func FuzzInsertLookup(f *testing.F) {
return return
} }
if scenario.seedA == scenario.seedB { seedA, seedB := scenario.seedA, scenario.seedB
return growthFactor := max(2, int(scenario.growthFactor))
capacity := int(scenario.capacity)
// If they are the same number, the hashes will clash, always causing an
// error.
if seedA == seedB {
t.Skip()
} }
fmt.Fprintf(os.Stderr, "seedA=%d seedB=%d capacity=%d growthFactor=%d\n",
seedA, seedB, capacity, growthFactor)
actual := cuckoo.NewCustomTable[uint32, uint32]( actual := cuckoo.NewCustomTable[uint32, uint32](
offsetHash(scenario.seedA), offsetHash(seedA),
offsetHash(scenario.seedB), offsetHash(seedB),
func(a, b uint32) bool { return a == b }, func(a, b uint32) bool { return a == b },
cuckoo.Capacity(capacity),
cuckoo.GrowthFactor(growthFactor),
) )
expected := map[uint32]uint32{} expected := map[uint32]uint32{}
for _, step := range scenario.steps { for _, step := range scenario.steps {
if step.drop { 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) delete(expected, step.key)
_, err = actual.Get(step.key) _, err := actual.Get(step.key)
assert.Error(err) assert.Error(err)
} else { } else {
err := actual.Put(step.key, step.value) _, err := actual.Put(step.key, step.value)
assert.NoError(err) assert.NoError(err)
expected[step.key] = step.value expected[step.key] = step.value

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@@ -23,7 +23,7 @@ func TestLoad(t *testing.T) {
table := NewTable[int, bool](Capacity(8)) table := NewTable[int, bool](Capacity(8))
for i := range 16 { for i := range 16 {
err := table.Put(i, true) _, err := table.Put(i, true)
assert.NoError(err) assert.NoError(err)
assert.Equal(float64(table.Size())/float64(table.TotalCapacity()), table.load()) assert.Equal(float64(table.Size())/float64(table.TotalCapacity()), table.load())
} }

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@@ -25,7 +25,7 @@ func TestAddItem(t *testing.T) {
key, value := 0, true key, value := 0, true
table := cuckoo.NewTable[int, bool]() table := cuckoo.NewTable[int, bool]()
err := table.Put(key, value) _, err := table.Put(key, value)
assert.NoError(err) assert.NoError(err)
assert.Equal(1, table.Size()) assert.Equal(1, table.Size())
@@ -38,7 +38,7 @@ func TestPutOverwrite(t *testing.T) {
table := cuckoo.NewTable[int, int]() table := cuckoo.NewTable[int, int]()
(table.Put(key, value)) (table.Put(key, value))
err := table.Put(key, newValue) _, err := table.Put(key, newValue)
assert.NoError(err) assert.NoError(err)
assert.Equal(1, table.Size()) assert.Equal(1, table.Size())
@@ -52,9 +52,9 @@ func TestSameHash(t *testing.T) {
hash := func(int) uint64 { return 0 } hash := func(int) uint64 { return 0 }
table := cuckoo.NewCustomTable[int, bool](hash, hash, cuckoo.DefaultEqualFunc[int]) table := cuckoo.NewCustomTable[int, bool](hash, hash, cuckoo.DefaultEqualFunc[int])
errA := table.Put(0, true) _, errA := table.Put(0, true)
errB := table.Put(1, true) _, errB := table.Put(1, true)
errC := table.Put(2, true) _, errC := table.Put(2, true)
assert.NoError(errA) assert.NoError(errA)
assert.NoError(errB) assert.NoError(errB)
@@ -76,7 +76,7 @@ func TestResizeCapacity(t *testing.T) {
) )
for table.TotalCapacity() == 16 { for table.TotalCapacity() == 16 {
err := table.Put(rand.Int(), true) _, err := table.Put(rand.Int(), true)
assert.NoError(err) assert.NoError(err)
} }
@@ -89,7 +89,7 @@ func TestPutMany(t *testing.T) {
for i := range 1_000 { for i := range 1_000 {
expected[i] = true expected[i] = true
err := actual.Put(i, true) _, err := actual.Put(i, true)
assert.NoError(err) assert.NoError(err)
} }
@@ -103,7 +103,7 @@ func TestGetMany(t *testing.T) {
table := cuckoo.NewTable[int, bool]() table := cuckoo.NewTable[int, bool]()
for i := range 1_000 { for i := range 1_000 {
err := table.Put(i, true) _, err := table.Put(i, true)
assert.NoError(err) assert.NoError(err)
} }
@@ -124,9 +124,9 @@ func TestDropExistingItem(t *testing.T) {
table := cuckoo.NewTable[int, bool]() table := cuckoo.NewTable[int, bool]()
(table.Put(key, value)) (table.Put(key, value))
err := table.Drop(key) had := table.Drop(key)
assert.NoError(err) assert.True(had)
assert.Equal(0, table.Size()) assert.Equal(0, table.Size())
assert.False(table.Has(key)) assert.False(table.Has(key))
} }
@@ -136,9 +136,9 @@ func TestDropNoItem(t *testing.T) {
key := 0 key := 0
table := cuckoo.NewTable[int, bool]() table := cuckoo.NewTable[int, bool]()
err := table.Drop(key) had := table.Drop(key)
assert.NoError(err) assert.False(had)
assert.Equal(0, table.Size()) assert.Equal(0, table.Size())
assert.False(table.Has(key)) assert.False(table.Has(key))
} }
@@ -152,10 +152,9 @@ func TestDropItemCapacity(t *testing.T) {
) )
startingCapacity := table.TotalCapacity() startingCapacity := table.TotalCapacity()
err := table.Drop(key) table.Drop(key)
endingCapacity := table.TotalCapacity() endingCapacity := table.TotalCapacity()
assert.NoError(err)
assert.Equal(0, table.Size()) assert.Equal(0, table.Size())
assert.Equal(uint64(128), startingCapacity) assert.Equal(uint64(128), startingCapacity)
assert.Equal(uint64(64), endingCapacity) assert.Equal(uint64(64), endingCapacity)
@@ -168,7 +167,7 @@ func TestPutNoCapacity(t *testing.T) {
cuckoo.Capacity(0), cuckoo.Capacity(0),
) )
err := table.Put(key, value) _, err := table.Put(key, value)
assert.NoError(err) assert.NoError(err)
assert.Equal(1, table.Size()) assert.Equal(1, table.Size())
@@ -184,9 +183,9 @@ func TestBadHashCapacity(t *testing.T) {
cuckoo.Capacity(20), cuckoo.Capacity(20),
) )
err1 := table.Put(0, true) _, err1 := table.Put(0, true)
err2 := table.Put(1, true) _, err2 := table.Put(1, true)
err3 := table.Put(2, true) _, err3 := table.Put(2, true)
assert.NoError(err1) assert.NoError(err1)
assert.NoError(err2) assert.NoError(err2)
@@ -201,11 +200,11 @@ func TestDropResizeCapacity(t *testing.T) {
cuckoo.Capacity(10), cuckoo.Capacity(10),
) )
err1 := table.Put(0, true) _, err1 := table.Put(0, true)
err2 := table.Put(1, 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()) assert.Equal(uint64(20), table.TotalCapacity())
} }
@@ -221,7 +220,7 @@ func TestNewTableBy(t *testing.T) {
func(u User) string { return u.id }, func(u User) string { return u.id },
) )
err := table.Put(User{nil, "1", "Robert"}, true) _, err := table.Put(User{nil, "1", "Robert"}, true)
assert.NoError(err) assert.NoError(err)
assert.Equal(1, table.Size()) assert.Equal(1, table.Size())

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@@ -10,7 +10,7 @@ import (
func Example_basic() { func Example_basic() {
table := cuckoo.NewTable[int, string]() table := cuckoo.NewTable[int, string]()
if err := table.Put(1, "Hello, World!"); err != nil { if _, err := table.Put(1, "Hello, World!"); err != nil {
fmt.Println("Put error:", err) fmt.Println("Put error:", err)
} }

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@@ -1,13 +0,0 @@
#:schema https://json.schemastore.org/pyproject.json
[tool.semantic_release]
commit_parser = "angular"
version_toml = []
tag_format = "v{version}"
[tool.semantic_release.remote]
type = "gitea"
domain = "git.maximhutz.com"
[tool.semantic_release.remote.token]
env = "GITEA_TOKEN"

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@@ -1,5 +1,7 @@
package cuckoo package cuckoo
import "fmt"
// DefaultCapacity is the initial capacity of a [Table]. It is inspired from // DefaultCapacity is the initial capacity of a [Table]. It is inspired from
// Java's [HashMap] implementation, which also uses 16. // Java's [HashMap] implementation, which also uses 16.
// //
@@ -10,11 +12,17 @@ const DefaultCapacity uint64 = 16
// hash table implementations use 2. // hash table implementations use 2.
const DefaultGrowthFactor uint64 = 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 // [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 { type settings struct {
growthFactor uint64 growthFactor uint64
@@ -27,19 +35,21 @@ type settings struct {
type Option func(*settings) type Option func(*settings)
// Capacity modifies the starting capacity of each bucket of the [Table]. The // Capacity modifies the starting capacity of each bucket of the [Table]. The
// value must be greater than 0. // value must be non-negative.
func Capacity(value int) Option { func Capacity(value int) Option {
return func(s *settings) { s.bucketSize = uint64(value) } if value < 0 {
} panic(fmt.Sprintf("go-cuckoo: Capacity must be non-negative, got %d", value))
}
// MinimumLoad modifies the [DefaultMinimumLoad] of the [Table]. The value must return func(s *settings) { s.bucketSize = uint64(value) }
// be between 0.00 and 1.00.
func MinimumLoad(value float64) Option {
return func(s *settings) { s.minLoadFactor = value }
} }
// GrowthFactor controls how much the capacity of the [Table] multiplies when // GrowthFactor controls how much the capacity of the [Table] multiplies when
// it must resize. The value must be greater than 1. // it must resize. The value must be greater than 1.
func GrowthFactor(value int) Option { func GrowthFactor(value int) Option {
if value < 2 {
panic(fmt.Sprintf("go-cuckoo: GrowthFactor must be greater than 1, got %d", value))
}
return func(s *settings) { s.growthFactor = uint64(value) } return func(s *settings) { s.growthFactor = uint64(value) }
} }

132
table.go
View File

@@ -45,30 +45,61 @@ func (t Table[K, V]) load() float64 {
return float64(t.Size()) / float64(t.TotalCapacity()) 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.bucketA.update(entry.Key, entry.Value) {
for k, v := range t.Entries() { return
entries = append(entries, entry[K, V]{k, v})
} }
t.bucketA.resize(capacity) if t.bucketB.update(entry.Key, entry.Value) {
t.bucketB.resize(capacity) return
}
for _, entry := range entries { for range t.maxEvictions() {
if err := t.Put(entry.key, entry.value); err != nil { if entry, homeless = t.bucketA.insert(entry); !homeless {
return err return
}
if entry, homeless = t.bucketB.insert(entry); !homeless {
return
} }
} }
return nil 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,
bucketA: t.bucketA.resized(capacity),
bucketB: t.bucketB.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() {
if _, failed := updated.insert(Entry[K, V]{k, v}); failed {
return false
}
}
*t = updated
return true
} }
// grow increases the table's capacity by the [Table.growthFactor]. If the // grow increases the table's capacity by the [Table.growthFactor]. If the
// capacity is 0, it increases it to 1. // 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 var newCapacity uint64
if t.TotalCapacity() == 0 { if t.TotalCapacity() == 0 {
@@ -82,7 +113,7 @@ func (t *Table[K, V]) grow() error {
// shrink reduces the table's capacity by the [Table.growthFactor]. It may // shrink reduces the table's capacity by the [Table.growthFactor]. It may
// reduce it down to 0. // 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.bucketA.capacity / t.growthFactor)
} }
@@ -106,49 +137,52 @@ func (t Table[K, V]) Has(key K) (exists bool) {
return err == nil return err == nil
} }
// 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) { // along with the last displaced entry.
if t.bucketA.update(key, value) { //
return nil // On failure, the returned entry and the current table contents together
} // preserve all previously inserted entries and the attempted entry.
func (t *Table[K, V]) Put(key K, value V) (displaced Entry[K, V], err error) {
var (
entry = Entry[K, V]{key, value}
homeless bool
)
if t.bucketB.update(key, value) { for range defaultGrowthLimit {
return nil if entry, homeless = t.insert(entry); !homeless {
} return
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 { // 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 entry, fmt.Errorf("bad hash: resize on load %d/%d", t.Size(), t.TotalCapacity())
}
// It is theoretically possible to have a table with a larger capacity
// that is valid. But this chance is astronomically small, so we ignore
// it in this implementation.
if grew := t.grow(); !grew {
return entry, fmt.Errorf("bad hash: could not redistribute entries into larger table")
} }
} }
if t.load() < t.minLoadFactor { return entry, fmt.Errorf("bad hash: could not place entry after %d resizes", defaultGrowthLimit)
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 // Drop removes a value for a key in the table. Returns whether the key had
// cannot be removed. // existed.
func (t *Table[K, V]) Drop(key K) (err error) { func (t *Table[K, V]) Drop(key K) bool {
t.bucketA.drop(key) occupied := t.bucketA.drop(key) || t.bucketB.drop(key)
t.bucketB.drop(key)
if t.load() < t.minLoadFactor { if t.load() < t.minLoadFactor {
return t.shrink() // The error is not handled here, because table-shrinking is an internal
// optimization.
t.shrink()
} }
return nil return occupied
} }
// Entries returns an unordered sequence of all key-value pairs in the table. // Entries returns an unordered sequence of all key-value pairs in the table.
@@ -156,7 +190,7 @@ func (t Table[K, V]) Entries() iter.Seq2[K, V] {
return func(yield func(K, V) bool) { return func(yield func(K, V) bool) {
for _, slot := range t.bucketA.slots { for _, slot := range t.bucketA.slots {
if slot.occupied { if slot.occupied {
if !yield(slot.key, slot.value) { if !yield(slot.Key, slot.Value) {
return return
} }
} }
@@ -164,7 +198,7 @@ func (t Table[K, V]) Entries() iter.Seq2[K, V] {
for _, slot := range t.bucketB.slots { for _, slot := range t.bucketB.slots {
if slot.occupied { if slot.occupied {
if !yield(slot.key, slot.value) { if !yield(slot.Key, slot.Value) {
return return
} }
} }
@@ -198,7 +232,7 @@ func NewCustomTable[K, V any](hashA, hashB Hash[K], compare EqualFunc[K], option
settings := &settings{ settings := &settings{
growthFactor: DefaultGrowthFactor, growthFactor: DefaultGrowthFactor,
bucketSize: DefaultCapacity, bucketSize: DefaultCapacity,
minLoadFactor: DefaultMinimumLoad, minLoadFactor: defaultMinimumLoad,
} }
for _, option := range options { for _, option := range options {