30 Commits

Author SHA1 Message Date
mvhutz 3806331768 revert: remove duplicate of analysis 2026-07-04 19:47:01 -04:00
mvhutz 2b610eaab6 chore: moved analysis over from contract adr 2026-07-04 19:42:41 -04:00
mvhutz 00ed7c8888 style: capitalization in status for adr template
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2026-07-03 21:41:42 -04:00
mvhutz b96d47fa1b style: no number in ADR title
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2026-07-03 21:30:35 -04:00
mvhutz df5a25d349 chore: move to docs/adr
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2026-07-03 21:29:04 -04:00
mvhutz 3f77e230a1 revert: no old adr
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2026-07-03 21:22:18 -04:00
mvhutz 7bc42e7101 style: worded consequences more as a checklist 2026-07-03 21:21:50 -04:00
mvhutz 56096bd83f feat: adr for design principles, template 2026-07-03 21:05:36 -04:00
mvhutz bfe2f152e1 Merge remote-tracking branch 'origin' into docs/contract-v2 2026-07-03 19:54:05 -04:00
mvhutz 05dbda496a ci: use go tool (#25)
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## Description

Tool versions were not pinned to the repository: this caused issues with upgrades.

## Changes

- Use `go tool` for `checkmake`, `gremlins`, `golangci-lint`, `godoc` and `govulncheck`.

### Design Decisions

## Checklist

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

Reviewed-on: #25
Co-authored-by: M.V. Hutz <git@maximhutz.me>
Co-committed-by: M.V. Hutz <git@maximhutz.me>
2026-07-03 23:53:17 +00:00
mvhutz 3aa5be87f2 feat: progress up to this point 2026-05-16 14:28:33 -04:00
mvhutz bd25bb69bd docs: congruency target 2026-05-09 16:57:58 -04:00
mvhutz 5c84ed7794 docs: DeleteFunc, Collect 2026-05-04 19:16:42 -04:00
mvhutz cddc205fe8 docs: insert, copy 2026-05-02 11:43:08 -04:00
mvhutz a72146ca9c docs: finished congruency, started target state 2026-05-01 17:38:52 -04:00
mvhutz f18d48a3c2 fix: wording 2026-04-29 20:53:07 -04:00
mvhutz 4464af781a feat: current contract list, started similarity 2026-04-29 20:52:15 -04:00
mvhutz 39548b4332 feat!: Drop returns bool, Put doesn't stack-overflow (#21)
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## 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>
2026-04-17 01:31:01 +00:00
mvhutz 29ba6bfd4d fix!: no mixed receiver types (#23)
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## Description

Currently, `bucket` and `Table` have mixed receiver types: some are pointer receviers, and others are value receivers.

As per the Go Wiki, [you can have value and pointer receivers, just don't mix them](https://go.dev/doc/faq#methods_on_values_or_pointers).

## Changes

- Replace all value receivers in `bucket` and `Table` with pointer receivers.

### Design Decisions

This decision was made due to the advice on the Go wiki.

## Checklist

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

Reviewed-on: #23
Co-authored-by: M.V. Hutz <git@maximhutz.me>
Co-committed-by: M.V. Hutz <git@maximhutz.me>
2026-04-16 03:27:48 +00:00
mvhutz 7cc1657403 refactor!: shorter constructors, bucketsubtable (#22)
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## Description

Currently, the name of `bucket` is a bit confusing, because it is considered a 'table' in literature (as well as the whole hash table). A `bucket` is better described as a 'subtable', which is used by the total hash table to perform cuckoo hashing.

In addition, the constructors `NewTable`, `NewTableBy`, and `NewCustomTable` were given shorter names, because the package name `cuckoo` already implies that `New*` would create a hash table with cuckoo hashing. This package has one use-case, and so it unambiguous what constructors produce.

## Changes

- `NewTable` -> `New`
- `NewTableBy` -> `NewBy`
- `NewCustomTable` -> `NewCustom`
- `bucket` -> `subtable`

### Design Decisions

- I would have renamed `Table` and `subtable` to map equivalents, but 'submap' implies that a certain subsection of the map is contained within it, which isn't quite right.
- I chose not to go with `Map` and `table`, because of the split naming convention.

## Checklist

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

Reviewed-on: #22
Co-authored-by: M.V. Hutz <git@maximhutz.me>
Co-committed-by: M.V. Hutz <git@maximhutz.me>
2026-04-16 03:15:39 +00:00
mvhutz 42c5b5f8f4 feat!: update get from (V, error) to (V, bool) (#20)
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## Description

Currently, the signature for `Table.Get` is `func (K) (V, error)`. This is not very Go-idiomatic, which prefers to return a boolean instead of an error. For instance, a built-in Go map is used like so:

```go
if value, ok := users[id]; !ok {
  // ...
}
```

Updating our table to look like that is best practice. In that same vein, to support direct lookup (i.e. `v := users[id]`), this PR also adds `Table.Find`.

## Changes

- BREAKING CHANGE: Update contract of `Table.Get` to `func (K) (V, bool)`. Returns 'false' is the item cannot be found, and 'true' if it is found.
- Add `Table.Find`.
- Updated tests and documentation to match the change.

### Design Decisions

- Chose to make this decision because throwing an error implies that there is something 'wrong' with the table. There is nothing wrong with the table; it is just that the item does not exist.

## Checklist

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

Reviewed-on: #20
Co-authored-by: M.V. Hutz <git@maximhutz.me>
Co-committed-by: M.V. Hutz <git@maximhutz.me>
2026-04-14 01:58:15 +00:00
mvhutz 867a1d49df feat: sentinel error ErrBadHash (#19)
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## Description

Currently, the errors are not sentinel, and so are hard to test for. This PR makes sure hash collision errors are accounted for.

## Changes

- Add `ErrBadHash`. Happens when there are too many collisions for an item to be added.

### Design Decisions

- Chose to name `ErrBadHash` over `ErrCycle` because the feedbach that the user should be given is to evaluate their hash functions. Cycle collision is a bit esoteric.

## Checklist

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

Reviewed-on: #19
Co-authored-by: M.V. Hutz <git@maximhutz.me>
Co-committed-by: M.V. Hutz <git@maximhutz.me>
2026-04-14 00:38:11 +00:00
mvhutz 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
mvhutz 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
mvhutz 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
mvhutz 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
mvhutz 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
mvhutz 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
mvhutz 41b09ae680 fix: remove redundant test TestRemove (#8)
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This test offers the same functionality as `TestAddItem`.

Reviewed-on: #8
Co-authored-by: M.V. Hutz <git@maximhutz.me>
Co-committed-by: M.V. Hutz <git@maximhutz.me>
2026-03-21 16:24:52 +00:00
mvhutz e00e6fcb1b docs: add logo for project, expand readme (#7)
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Reviewed-on: #7
Co-authored-by: M.V. Hutz <git@maximhutz.me>
Co-committed-by: M.V. Hutz <git@maximhutz.me>
2026-03-21 01:14:17 +00:00
29 changed files with 2385 additions and 299 deletions
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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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@@ -0,0 +1,17 @@
---
name: "New Pull Request"
about: "Standard PR template"
title: ""
ref: "main"
---
## Description
## Changes
### Design Decisions
## Checklist
- [ ] Tests pass
- [ ] Docs updated
+23 -9
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@@ -6,6 +6,19 @@ on:
pull_request:
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:
name: Go Lint
runs-on: ubuntu-latest
@@ -19,9 +32,8 @@ jobs:
- name: Check go mod tidy
run: go mod tidy && git diff --exit-code go.mod go.sum
- uses: golangci/golangci-lint-action@v7
with:
version: latest
- name: Run linter
run: make lint-go
lint-makefile:
name: Makefile Lint
@@ -33,12 +45,17 @@ jobs:
with:
go-version-file: go.mod
- name: Install gremlins
run: go install github.com/checkmake/checkmake/cmd/checkmake@latest
- name: Run mutation tests
run: make lint-makefile
lint-markdown:
name: Markdown Lint
runs-on: ubuntu-latest
steps:
- uses: actions/checkout@v4
- uses: DavidAnson/markdownlint-cli2-action@v19
test-unit:
name: Unit Tests
runs-on: ubuntu-latest
@@ -75,8 +92,5 @@ jobs:
with:
go-version-file: go.mod
- name: Install gremlins
run: go install github.com/go-gremlins/gremlins/cmd/gremlins@latest
- name: Run mutation tests
run: make test-mutation
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@@ -24,4 +24,3 @@ go.work.sum
# env file
.env
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@@ -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:
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@@ -0,0 +1,17 @@
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
+10 -11
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@@ -1,20 +1,16 @@
.PHONY: all help install clean test-unit test-mutation test-fuzz test docs lint-go lint-makefile lint
.PHONY: all help install clean test-unit test-mutation test-fuzz test docs lint-go lint-makefile lint-markdown lint
help: ## Show this help
@grep -E '^[a-zA-Z_-]+:.*##' $(MAKEFILE_LIST) | awk -F ':.*## ' '{printf " %-15s %s\n", $$1, $$2}'
install: ## Install dev tools
go install github.com/golangci/golangci-lint/cmd/golangci-lint@latest
go install github.com/checkmake/checkmake/cmd/checkmake@latest
go install github.com/go-gremlins/gremlins/cmd/gremlins@latest
go install golang.org/x/tools/cmd/godoc@latest
go install golang.org/x/vuln/cmd/govulncheck@latest
go mod download
test-unit: ## Run unit tests with coverage
go test ./... -cover -v
test-mutation: ## Run mutation tests with gremlins
gremlins unleash
go tool gremlins unleash
FUZZ_TIME ?= 30
@@ -27,16 +23,19 @@ test-fuzz: ## Run all fuzz tests for 30s each
test: test-unit test-mutation test-fuzz ## Run all tests
lint-go: ## Lint Go code
golangci-lint run ./...
go tool golangci-lint run ./...
lint-makefile: ## Lint the Makefile
checkmake Makefile
go tool checkmake Makefile
lint: lint-go lint-makefile ## Lint all code
lint-markdown: ## Lint Markdown files
docker run --rm -v $(CURDIR):/workdir davidanson/markdownlint-cli2 "**/*.md"
lint: lint-go lint-makefile lint-markdown ## Lint all code
docs: ## Serve godoc locally
@echo ">>> Visit: http://localhost:6060/pkg/$$(go list -m)"
godoc -http=:6060
go tool godoc -http=:6060
clean: ## Clean build and test caches
go clean -cache -testcache
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@@ -1,3 +1,3 @@
# go-cuckoo
# <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.
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).
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@@ -0,0 +1 @@
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-103
View File
@@ -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),
}
}
+1 -1
View File
@@ -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.
+1 -1
View File
@@ -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))
+26 -11
View File
@@ -1,7 +1,9 @@
package cuckoo_test
import (
"fmt"
"maps"
"os"
"testing"
"github.com/stretchr/testify/assert"
@@ -26,6 +28,7 @@ type fuzzStep struct {
type fuzzScenario struct {
seedA, seedB uint32
capacity, growthFactor uint8
steps []fuzzStep
}
@@ -40,35 +43,47 @@ func FuzzInsertLookup(f *testing.F) {
return
}
if scenario.seedA == scenario.seedB {
return
seedA, seedB := scenario.seedA, scenario.seedB
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()
}
actual := cuckoo.NewCustomTable[uint32, uint32](
offsetHash(scenario.seedA),
offsetHash(scenario.seedB),
fmt.Fprintf(os.Stderr, "seedA=%d seedB=%d capacity=%d growthFactor=%d\n",
seedA, seedB, capacity, growthFactor)
actual := cuckoo.NewCustom[uint32, uint32](
offsetHash(seedA),
offsetHash(seedB),
func(a, b uint32) bool { return a == b },
cuckoo.Capacity(capacity),
cuckoo.GrowthFactor(growthFactor),
)
expected := map[uint32]uint32{}
for _, step := range scenario.steps {
if step.drop {
err := actual.Drop(step.key)
assert.NoError(err)
ok := actual.Drop(step.key)
_, has := expected[step.key]
assert.Equal(ok, has)
delete(expected, step.key)
_, err = actual.Get(step.key)
assert.Error(err)
_, ok = actual.Get(step.key)
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)
assert.NoError(err)
found, ok := actual.Get(step.key)
assert.True(ok)
assert.Equal(step.value, found)
}
+2 -2
View File
@@ -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)
+25 -40
View File
@@ -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)
@@ -108,37 +108,25 @@ 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)
}
}
}
func TestRemove(t *testing.T) {
assert := assert.New(t)
table := cuckoo.NewTable[int, bool]()
assert.False(table.Has(0))
err := table.Put(0, true)
assert.NoError(err)
assert.True(table.Has(0))
}
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))
}
@@ -146,11 +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))
}
@@ -158,16 +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)
@@ -176,7 +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),
)
@@ -189,7 +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 },
@@ -209,15 +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())
}
@@ -229,9 +216,7 @@ func TestNewTableBy(t *testing.T) {
}
assert := assert.New(t)
table := cuckoo.NewTableBy[User, bool](
func(u User) string { return u.id },
)
table := cuckoo.NewBy[User, bool](func(u User) string { return u.id })
err := table.Put(User{nil, "1", "Robert"}, true)
+5 -2
View File
@@ -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
// a table with any key type using [NewCustomTable]. Custom [Hash] functions and
// While a [New] only supports comparable keys by default, you can create
// 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
+6 -6
View File
@@ -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 {
fmt.Println("Error:", err)
if item, ok := table.Get(1); !ok {
fmt.Println("Not Found 1!")
} else {
fmt.Println("Found 1:", item)
}
if item, err := table.Get(0); err != nil {
fmt.Println("Error:", err)
if item, ok := table.Get(0); !ok {
fmt.Println("Not Found 0!")
} else {
fmt.Println("Found 0:", item)
}
// Output:
// Found 1: Hello, World!
// Error: key '0' not found
// Not Found 0!
}
+15
View File
@@ -0,0 +1,15 @@
# Title
**Status**: <!-- Proposed, accepted, rejected, etc... -->
## Context
<!-- What is the issue that we're seeing that is motivating this decision or change? -->
## Decision
<!-- What is the change that we're proposing and/or doing? -->
## Consequences
<!-- What becomes easier or more difficult to do because of this change? -->
+44
View File
@@ -0,0 +1,44 @@
# Adopt Congruent and Familiar Design For `go-cuckoo`
**Status**: Proposed
## Context
I built `go-cuckoo`'s API interface without design intent.
Up until now, I paid more attention implementing the underlying functionality of the cuckoo hashing.
With the fundamentals of the algorithm built, I should revisit the interface.
The goal of this project was to create an implementation of cuckoo hashing, while adhering to Go's idioms, and being as usable as possible.
While the implementation does work, it lacks direction.
## Decision
To resolve this, I'm enforcing two new principles onto the contract of `go-cuckoo`:
- **Congruency**:
A `go-cuckoo` table should have the same core functionality as Go's built-in map.
- **Familiarity**:
A `go-cuckoo` table should behave similarly to Go's standard map, so users will intuitively know how to use it.
In effect, its users will carry less cognitive load.
These principles should _guide_ the public interface of `go-cuckoo`.
Neither should be treated absolutely, though.
The behavior of `go-cuckoo` is distinct from `map`.
Do not equate them.
## Consequences
1. The repository should support both design principles.
- [ ] Update the `README.md` and `doc.go` to reflect these principles.
- [ ] Update the contributing guide and pull request template to require these principles are met.
2. The repository should contain a living document, describing the interface differences between `go-cuckoo` and `map`.
I should prioritize limiting any incongruencies.
- [ ] Produce the first draft to uncover any current incongruencies.
- [ ] Link the document to the `README.md`.
3. Analyze the familiarity of `go-cuckoo`'s current interface.
Unlike the analysis of congruency, this should be a one time document.
Familiarity is implicit to users, and does not need to be referenced.
But, any rationale should be documented in commit messages, or future ADRs.
- [ ] Produce the analysis document.
- [ ] Resolve any issues found.
+227 -1
View File
@@ -4,7 +4,225 @@ go 1.25.6
require github.com/stretchr/testify v1.11.1
require github.com/kr/pretty v0.3.1 // indirect
require (
4d63.com/gocheckcompilerdirectives v1.3.0 // indirect
4d63.com/gochecknoglobals v0.2.2 // indirect
charm.land/lipgloss/v2 v2.0.3 // indirect
codeberg.org/chavacava/garif v0.2.0 // indirect
codeberg.org/polyfloyd/go-errorlint v1.9.0 // indirect
dev.gaijin.team/go/exhaustruct/v4 v4.0.0 // indirect
dev.gaijin.team/go/golib v0.6.0 // indirect
github.com/4meepo/tagalign v1.4.3 // indirect
github.com/Abirdcfly/dupword v0.1.7 // indirect
github.com/AdminBenni/iota-mixing v1.0.0 // indirect
github.com/AlwxSin/noinlineerr v1.0.5 // indirect
github.com/Antonboom/errname v1.1.1 // indirect
github.com/Antonboom/nilnil v1.1.1 // indirect
github.com/Antonboom/testifylint v1.6.4 // indirect
github.com/BurntSushi/toml v1.6.0 // indirect
github.com/ClickHouse/clickhouse-go-linter v1.2.0 // indirect
github.com/Djarvur/go-err113 v0.1.1 // indirect
github.com/MakeNowJust/heredoc v1.0.0 // indirect
github.com/Masterminds/semver/v3 v3.5.0 // indirect
github.com/MirrexOne/unqueryvet v1.5.4 // indirect
github.com/OpenPeeDeeP/depguard/v2 v2.2.1 // indirect
github.com/alecthomas/chroma/v2 v2.24.1 // indirect
github.com/alecthomas/go-check-sumtype v0.3.1 // indirect
github.com/alexkohler/nakedret/v2 v2.0.6 // indirect
github.com/alexkohler/prealloc v1.1.0 // indirect
github.com/alfatraining/structtag v1.0.0 // indirect
github.com/alingse/asasalint v0.0.11 // indirect
github.com/alingse/nilnesserr v0.2.0 // indirect
github.com/ashanbrown/forbidigo/v2 v2.3.1 // indirect
github.com/ashanbrown/makezero/v2 v2.2.1 // indirect
github.com/beorn7/perks v1.0.1 // indirect
github.com/bkielbasa/cyclop v1.2.3 // indirect
github.com/blizzy78/varnamelen v0.8.0 // indirect
github.com/bluekeyes/go-gitdiff v0.8.1 // indirect
github.com/bombsimon/wsl/v4 v4.7.0 // indirect
github.com/bombsimon/wsl/v5 v5.8.0 // indirect
github.com/breml/bidichk v0.3.3 // indirect
github.com/breml/errchkjson v0.4.1 // indirect
github.com/butuzov/ireturn v0.4.1 // indirect
github.com/butuzov/mirror v1.3.0 // indirect
github.com/catenacyber/perfsprint v0.10.1 // indirect
github.com/ccojocar/zxcvbn-go v1.0.4 // indirect
github.com/cespare/xxhash/v2 v2.3.0 // indirect
github.com/charithe/durationcheck v0.0.11 // indirect
github.com/charmbracelet/colorprofile v0.4.3 // indirect
github.com/charmbracelet/ultraviolet v0.0.0-20251205161215-1948445e3318 // indirect
github.com/charmbracelet/x/ansi v0.11.7 // indirect
github.com/charmbracelet/x/term v0.2.2 // indirect
github.com/charmbracelet/x/termios v0.1.1 // indirect
github.com/charmbracelet/x/windows v0.2.2 // indirect
github.com/checkmake/checkmake v0.3.2 // indirect
github.com/ckaznocha/intrange v0.3.1 // indirect
github.com/clipperhouse/displaywidth v0.11.0 // indirect
github.com/clipperhouse/uax29/v2 v2.7.0 // indirect
github.com/curioswitch/go-reassign v0.3.0 // indirect
github.com/daixiang0/gci v0.13.7 // indirect
github.com/dave/dst v0.27.3 // indirect
github.com/denis-tingaikin/go-header v0.5.0 // indirect
github.com/dlclark/regexp2 v1.12.0 // indirect
github.com/ettle/strcase v0.2.0 // indirect
github.com/fatih/color v1.19.0 // indirect
github.com/fatih/structtag v1.2.0 // indirect
github.com/firefart/nonamedreturns v1.0.6 // indirect
github.com/fsnotify/fsnotify v1.9.0 // indirect
github.com/fzipp/gocyclo v0.6.0 // indirect
github.com/ghostiam/protogetter v0.3.20 // indirect
github.com/go-critic/go-critic v0.14.3 // indirect
github.com/go-gremlins/gremlins v0.6.0 // indirect
github.com/go-ini/ini v1.67.0 // indirect
github.com/go-toolsmith/astcast v1.1.0 // indirect
github.com/go-toolsmith/astcopy v1.1.0 // indirect
github.com/go-toolsmith/astequal v1.2.0 // indirect
github.com/go-toolsmith/astfmt v1.1.0 // indirect
github.com/go-toolsmith/astp v1.1.0 // indirect
github.com/go-toolsmith/strparse v1.1.0 // indirect
github.com/go-toolsmith/typep v1.1.0 // indirect
github.com/go-viper/mapstructure/v2 v2.5.0 // indirect
github.com/go-xmlfmt/xmlfmt v1.1.3 // indirect
github.com/gobwas/glob v0.2.3 // indirect
github.com/godoc-lint/godoc-lint v0.11.2 // indirect
github.com/gofrs/flock v0.13.0 // indirect
github.com/golang/protobuf v1.5.3 // indirect
github.com/golangci/asciicheck v0.5.0 // indirect
github.com/golangci/dupl v0.0.0-20260401084720-c99c5cf5c202 // indirect
github.com/golangci/go-printf-func-name v0.1.1 // indirect
github.com/golangci/gofmt v0.0.0-20250106114630-d62b90e6713d // indirect
github.com/golangci/golangci-lint/v2 v2.12.2 // indirect
github.com/golangci/golines v0.15.0 // indirect
github.com/golangci/misspell v0.8.0 // indirect
github.com/golangci/plugin-module-register v0.1.2 // indirect
github.com/golangci/revgrep v0.8.0 // indirect
github.com/golangci/rowserrcheck v0.0.0-20260419091836-c5f79b8a11ba // indirect
github.com/golangci/swaggoswag v0.0.0-20250504205917-77f2aca3143e // indirect
github.com/golangci/unconvert v0.0.0-20250410112200-a129a6e6413e // indirect
github.com/google/go-cmp v0.7.0 // indirect
github.com/gordonklaus/ineffassign v0.2.0 // indirect
github.com/gostaticanalysis/analysisutil v0.7.1 // indirect
github.com/gostaticanalysis/comment v1.5.0 // indirect
github.com/gostaticanalysis/forcetypeassert v0.2.0 // indirect
github.com/gostaticanalysis/nilerr v0.1.2 // indirect
github.com/hako/durafmt v0.0.0-20210608085754-5c1018a4e16b // indirect
github.com/hashicorp/go-immutable-radix/v2 v2.1.0 // indirect
github.com/hashicorp/go-version v1.9.0 // indirect
github.com/hashicorp/golang-lru/v2 v2.0.7 // indirect
github.com/hexops/gotextdiff v1.0.3 // indirect
github.com/inconshreveable/mousetrap v1.1.0 // indirect
github.com/jgautheron/goconst v1.10.0 // indirect
github.com/jjti/go-spancheck v0.6.5 // indirect
github.com/julz/importas v0.2.0 // indirect
github.com/karamaru-alpha/copyloopvar v1.2.2 // indirect
github.com/kisielk/errcheck v1.10.0 // indirect
github.com/kkHAIKE/contextcheck v1.1.6 // indirect
github.com/kulti/thelper v0.7.1 // indirect
github.com/kunwardeep/paralleltest v1.0.15 // indirect
github.com/lasiar/canonicalheader v1.1.2 // indirect
github.com/ldez/exptostd v0.4.5 // indirect
github.com/ldez/gomoddirectives v0.8.0 // indirect
github.com/ldez/grignotin v0.10.1 // indirect
github.com/ldez/structtags v0.6.1 // indirect
github.com/ldez/tagliatelle v0.7.2 // indirect
github.com/ldez/usetesting v0.5.0 // indirect
github.com/leonklingele/grouper v1.1.2 // indirect
github.com/lucasb-eyer/go-colorful v1.4.0 // indirect
github.com/macabu/inamedparam v0.2.0 // indirect
github.com/manuelarte/embeddedstructfieldcheck v0.4.0 // indirect
github.com/manuelarte/funcorder v0.6.0 // indirect
github.com/maratori/testableexamples v1.0.1 // indirect
github.com/maratori/testpackage v1.1.2 // indirect
github.com/matoous/godox v1.1.0 // indirect
github.com/mattn/go-colorable v0.1.14 // indirect
github.com/mattn/go-isatty v0.0.20 // indirect
github.com/mattn/go-runewidth v0.0.23 // indirect
github.com/matttproud/golang_protobuf_extensions v1.0.1 // indirect
github.com/mgechev/revive v1.15.0 // indirect
github.com/mitchellh/go-homedir v1.1.0 // indirect
github.com/moricho/tparallel v0.3.2 // indirect
github.com/muesli/cancelreader v0.2.2 // indirect
github.com/nakabonne/nestif v0.3.1 // indirect
github.com/nishanths/exhaustive v0.12.0 // indirect
github.com/nishanths/predeclared v0.2.2 // indirect
github.com/nunnatsa/ginkgolinter v0.23.0 // indirect
github.com/olekukonko/cat v0.0.0-20250911104152-50322a0618f6 // indirect
github.com/olekukonko/errors v1.1.0 // indirect
github.com/olekukonko/ll v0.1.3 // indirect
github.com/olekukonko/tablewriter v1.1.2 // indirect
github.com/pelletier/go-toml/v2 v2.3.1 // indirect
github.com/prometheus/client_golang v1.12.1 // indirect
github.com/prometheus/client_model v0.2.0 // indirect
github.com/prometheus/common v0.32.1 // indirect
github.com/prometheus/procfs v0.7.3 // indirect
github.com/quasilyte/go-ruleguard v0.4.5 // indirect
github.com/quasilyte/go-ruleguard/dsl v0.3.23 // indirect
github.com/quasilyte/gogrep v0.5.0 // indirect
github.com/quasilyte/regex/syntax v0.0.0-20210819130434-b3f0c404a727 // indirect
github.com/quasilyte/stdinfo v0.0.0-20220114132959-f7386bf02567 // indirect
github.com/raeperd/recvcheck v0.2.0 // indirect
github.com/rivo/uniseg v0.4.7 // indirect
github.com/rogpeppe/go-internal v1.14.1 // indirect
github.com/ryancurrah/gomodguard v1.4.1 // indirect
github.com/ryancurrah/gomodguard/v2 v2.1.3 // indirect
github.com/ryanrolds/sqlclosecheck v0.6.0 // indirect
github.com/sagikazarmark/locafero v0.12.0 // indirect
github.com/sanposhiho/wastedassign/v2 v2.1.0 // indirect
github.com/santhosh-tekuri/jsonschema/v6 v6.0.2 // indirect
github.com/sashamelentyev/interfacebloat v1.1.0 // indirect
github.com/sashamelentyev/usestdlibvars v1.29.0 // indirect
github.com/securego/gosec/v2 v2.26.1 // indirect
github.com/sirupsen/logrus v1.9.4 // indirect
github.com/sivchari/containedctx v1.0.3 // indirect
github.com/sonatard/noctx v0.5.1 // indirect
github.com/sourcegraph/go-diff v0.8.0 // indirect
github.com/spf13/afero v1.15.0 // indirect
github.com/spf13/cast v1.10.0 // indirect
github.com/spf13/cobra v1.10.2 // indirect
github.com/spf13/pflag v1.0.10 // indirect
github.com/spf13/viper v1.21.0 // indirect
github.com/ssgreg/nlreturn/v2 v2.2.1 // indirect
github.com/stbenjam/no-sprintf-host-port v0.3.1 // indirect
github.com/stretchr/objx v0.5.2 // indirect
github.com/subosito/gotenv v1.6.0 // indirect
github.com/tetafro/godot v1.5.6 // indirect
github.com/timakin/bodyclose v0.0.0-20260129054331-73d1f95b84b4 // indirect
github.com/timonwong/loggercheck v0.11.0 // indirect
github.com/tomarrell/wrapcheck/v2 v2.12.0 // indirect
github.com/tommy-muehle/go-mnd/v2 v2.5.1 // indirect
github.com/ultraware/funlen v0.2.0 // indirect
github.com/ultraware/whitespace v0.2.0 // indirect
github.com/uudashr/gocognit v1.2.1 // indirect
github.com/uudashr/iface v1.4.2 // indirect
github.com/xen0n/gosmopolitan v1.3.0 // indirect
github.com/xo/terminfo v0.0.0-20220910002029-abceb7e1c41e // indirect
github.com/yagipy/maintidx v1.0.0 // indirect
github.com/yeya24/promlinter v0.3.0 // indirect
github.com/ykadowak/zerologlint v0.1.5 // indirect
github.com/yuin/goldmark v1.7.13 // indirect
gitlab.com/bosi/decorder v0.4.2 // indirect
go-simpler.org/musttag v0.14.0 // indirect
go-simpler.org/sloglint v0.12.0 // indirect
go.augendre.info/arangolint v0.4.0 // indirect
go.augendre.info/fatcontext v0.9.0 // indirect
go.uber.org/multierr v1.10.0 // indirect
go.uber.org/zap v1.27.0 // indirect
go.yaml.in/yaml/v3 v3.0.4 // indirect
golang.org/x/exp/typeparams v0.0.0-20260209203927-2842357ff358 // indirect
golang.org/x/mod v0.35.0 // indirect
golang.org/x/sync v0.20.0 // indirect
golang.org/x/sys v0.43.0 // indirect
golang.org/x/telemetry v0.0.0-20260421165255-392afab6f40e // indirect
golang.org/x/text v0.36.0 // indirect
golang.org/x/tools v0.44.0 // indirect
golang.org/x/tools/cmd/godoc v0.1.0-deprecated // indirect
golang.org/x/tools/godoc v0.1.0-deprecated // indirect
golang.org/x/vuln v1.3.0 // indirect
google.golang.org/protobuf v1.36.10 // indirect
honnef.co/go/tools v0.7.0 // indirect
mvdan.cc/gofumpt v0.9.2 // indirect
mvdan.cc/unparam v0.0.0-20251027182757-5beb8c8f8f15 // indirect
)
require (
github.com/davecgh/go-spew v1.1.1 // indirect
@@ -12,3 +230,11 @@ require (
github.com/trailofbits/go-fuzz-utils v0.0.0-20260318143407-0907cafe7589
gopkg.in/yaml.v3 v3.0.1 // indirect
)
tool (
github.com/checkmake/checkmake/cmd/checkmake
github.com/go-gremlins/gremlins/cmd/gremlins
github.com/golangci/golangci-lint/v2/cmd/golangci-lint
golang.org/x/tools/cmd/godoc
golang.org/x/vuln/cmd/govulncheck
)
+984 -4
View File
File diff suppressed because it is too large Load Diff
+23 -13
View File
@@ -1,5 +1,7 @@
package cuckoo
import "fmt"
// DefaultCapacity is the initial capacity of a [Table]. It is inspired from
// Java's [HashMap] implementation, which also uses 16.
//
@@ -7,14 +9,20 @@ package cuckoo
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].
// The value of 5% is taken from [libcuckoo].
// defaultMinimumLoad is the default lowest acceptable occupancy of a [Table].
// 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
@@ -23,23 +31,25 @@ 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
// value must be greater than 0.
// Capacity modifies the starting capacity of each subtable of the [Table]. The
// value must be non-negative.
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
// be between 0.00 and 1.00.
func MinimumLoad(value float64) Option {
return func(s *settings) { s.minLoadFactor = value }
return func(s *settings) { s.bucketSize = uint64(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 {
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) }
}
+107
View File
@@ -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),
}
}
+132 -86
View File
@@ -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
// one with [NewTable]. Or if you want more granularity, use [NewTableBy] or
// [NewCustomTable].
// ErrBadHash occurs when the hashes given to a [Table] cause too many key
// collisions. Discard the old table, rebuild it from your source data, and try:
//
// 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 {
return t.bucketA.capacity + t.bucketB.capacity
func (t *Table[K, V]) TotalCapacity() uint64 {
return t.tableA.capacity + t.tableB.capacity
}
// Size returns how many slots are filled in the [Table].
func (t Table[K, V]) Size() int {
return int(t.bucketA.size + t.bucketB.size)
func (t *Table[K, V]) Size() int {
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,
// and fills them back up again. It is a helper function for [Table.grow] and
// [Table.shrink]; use them instead.
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})
// insert attempts to put/update an entry in the table, without modifying the
// size of the table. Returns a displaced entry and 'homeless = true' if an
// entry could not be placed after exhausting evictions.
func (t *Table[K, V]) insert(entry entry[K, V]) (displaced entry[K, V], homeless bool) {
if t.tableA.update(entry.key, entry.value) {
return
}
t.bucketA.resize(capacity)
t.bucketB.resize(capacity)
if t.tableB.update(entry.key, entry.value) {
return
}
for _, entry := range entries {
if err := t.Put(entry.key, entry.value); err != nil {
return err
for range t.maxEvictions() {
if entry, homeless = t.tableA.insert(entry); !homeless {
return
}
if entry, homeless = t.tableB.insert(entry); !homeless {
return
}
}
return nil
return entry, true
}
// grow increases the table's capacity by the [Table.growthFactor]. If the
// 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() {
if _, failed := updated.insert(entry[K, V]{k, v}); failed {
return false
}
}
*t = *updated
return true
}
// 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 {
return t.resize(t.bucketA.capacity / t.growthFactor)
func (t *Table[K, V]) shrink() bool {
return t.resize(t.tableA.capacity / t.growthFactor)
}
// Get fetches the value for a key in the [Table]. Returns an error if no value
// is found.
func (t Table[K, V]) Get(key K) (value V, err error) {
if item, ok := t.bucketA.get(key); ok {
return item, nil
// Get fetches the value for a key in the [Table]. Matches the comma-ok pattern
// of a builtin map; see [Table.Find] for plain indexing.
func (t *Table[K, V]) Get(key K) (value V, ok bool) {
if item, ok := t.tableA.get(key); ok {
return item, true
}
if item, ok := t.bucketB.get(key); ok {
return item, nil
if item, ok := t.tableB.get(key); ok {
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) {
_, err := t.Get(key)
return err == nil
func (t *Table[K, V]) Has(key K) (exists bool) {
_, exists = t.Get(key)
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) {
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
}
var (
entry = entry[K, V]{key, value}
homeless bool
)
for range defaultGrowthLimit {
if entry, homeless = t.insert(entry); !homeless {
return
}
// Both this and the growth limit are necessary: this catches bad hashes
// early when the table is sparse, while the latter catches cases where
// growing never helps.
if t.load() < t.minLoadFactor {
return fmt.Errorf("bad hash: resize on load %d/%d = %f", t.Size(), t.TotalCapacity(), t.load())
return fmt.Errorf("hash functions produced a cycle at load %d/%d: %w", t.Size(), t.TotalCapacity(), ErrBadHash)
}
if err := t.grow(); err != nil {
return err
// 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 fmt.Errorf("could not redistribute entries into larger table: %w", ErrBadHash)
}
}
return t.Put(entry.key, entry.value)
return fmt.Errorf("could not place entry after %d resizes: %w", defaultGrowthLimit, ErrBadHash)
}
// 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)
// 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 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.
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 ...]".
func (t Table[K, V]) String() string {
// "table[k1:v1 k2:v2 ...]".
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),
bucketB: newBucket[K, V](settings.bucketSize, hashB, compare),
tableA: newSubtable[K, V](settings.bucketSize, hashA, 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] {
return NewCustomTable[K, V](
func NewBy[K, V any, C comparable](keyFunc func(K) C, options ...Option) *Table[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].
func NewTable[K comparable, V any](options ...Option) *Table[K, V] {
return NewCustomTable[K, V](NewDefaultHash[K](), NewDefaultHash[K](), DefaultEqualFunc[K], options...)
// [NewBy] or [NewCustom].
func New[K comparable, V any](options ...Option) *Table[K, V] {
return NewCustom[K, V](NewDefaultHash[K](), NewDefaultHash[K](), DefaultEqualFunc[K], options...)
}
+643
View File
@@ -0,0 +1,643 @@
# Designing an Idiomatic API Interface
- [Designing an Idiomatic API Interface](#designing-an-idiomatic-api-interface)
- [Current State](#current-state)
- [Interface of the Built-in Map](#interface-of-the-built-in-map)
- [Interface of `go-cuckoo`](#interface-of-go-cuckoo)
- [Determining Congruency](#determining-congruency)
- [Determining Familiarity](#determining-familiarity)
- [Target State](#target-state)
- [Solving Congruency](#solving-congruency)
We (the maintainers) built `go-cuckoo`'s API interface without design intent.
Up until now, we paid more attention implementing the underlying functionality of the cuckoo hashing.
With the fundamentals of the algorithm built, we should revisit the interface.
It should align closer to the following principles:
- **Congruency**
A `go-cuckoo` table should have the same core functionality as Go's built-in map.
- **Familiarity**
A `go-cuckoo` table should behave similarly to Go's standard map, so users will intuitively know how to use it.
In effect, its users will carry less cognitive load.
## Current State
### Interface of the Built-in Map
Listed below is every interface provided by Go to the built-in map object.
Also included, are the functions from the package `maps` in the standard library.
<details>
<summary>Interfaces</summary>
| # | Built-in Interface | Description |
| --- | ---------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------- |
| 1 | `m := make(map[K]V)` | Returns an empty map using the built-in `make()` function. |
| 2 | `m := make(map[K]V, hint)` | Returns an empty map using `make()`, with a capacity 'hint'. This hint is how many items the map expects to hold, _not_ a measure of how large it is. |
| 3 | `m := map[K]V{...}` | Returns a map, which may be filled with entries in the ellipsis (optional). |
| 4 | `var m map[K]V` | Defines an empty _variable_ that holds a map. This differs from #1 because `m` is uninitialized (nil) here. |
| 5 | `m[k] := v` | Assigns the value of `k` to `v`. |
| 6 | `v := m[k]` | Returns the value of `k` if it exists. Otherwise, `v` is uninitialized. |
| 7 | `v, ok := m[k]` | Similar to #6, except `ok` is equal to whether `v` is initialized. This is comma-ok notation. |
| 8 | `for k, v := range m` | Iterates over every key-value pair in `m`. The order is random. |
| 9 | `delete(m, k)` | Unassigns the value `k`. Returns no value. |
| 10 | `clear(m)` | Unassigns all keys in `m`. Returns no value. |
| 11 | `n := len(m)` | Returns the number of entries in `m`. If nil, `m` returns 0. |
| 12 | `m2 := maps.Clone(m)` | Returns a copy of `m`. |
| 13 | `maps.Copy(dst, src)` | Assigns every entry of `src` in `dst`. |
| 14 | `ok := maps.Equal(m1, m2)` | Returns true iff `m1` and `m2` the same entries. |
| 15 | `ok := maps.EqualFunc(m1, m2, fn)` | Like #14, but with a custom comparator for non-comparable values. |
| 16 | `maps.DeleteFunc(m, fn)` | Removes every entry in `m` which satisfies `fn`. Returns no value. |
| 17 | `it2 := maps.All(m)` | Returns an 2D iterator over every key-value pair. |
| 18 | `it := maps.Keys(m)` | Returns an iterator over every key. |
| 19 | `it := maps.Values(m)` | Returns an iterator over every value. There can be duplicates. |
| 20 | `m := maps.Collect(seq)` | Returns a map, with every entry defined in a 2D iterator over key-value pairs. |
| 21 | `maps.Insert(m, seq)` | Assigns to `m` all key-value pairs in 2D iterator `seq`. Returns no value. |
</details>
### Interface of `go-cuckoo`
On the other hand, here is the current contract for `go-cuckoo`.
<details>
<summary>Interfaces</summary>
| # | `go-cuckoo` Interface | Description |
| --- | -------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------- |
| 1 | `m := New(opts...)` | Creates a table using the default hash and equal function. The options configure its behavior. Confined to comparable keys. |
| 2 | `m := NewBy(keyFunc, opts...)` | Like #1, but allows any key type. A `keyFunc` is used to derive a comparable key. |
| 3 | `m := NewCustom(hashA, hashB, equalFunc, opts...)` | Like #1, but allows control over the hashes used to allow any key type. An `equalFunc` determines key equality. |
| 4 | `seq := m.Entries()` | Returns an unordered 2D iterator of all key-value pairs in the table. |
| 5 | `v := m.Find(k)` | Removes the value for `k`. Returns true if `k` existed. |
| 6 | `v, ok := m.Get(k)` | Returns the value for `k` in the table. Also, returns true if the `k` exists, otherwise false. When false, `v` is undefined. |
| 7 | `ok := m.Has(k)` | Returns true if `k` is in the table. |
| 8 | `err := m.Put(k, v)` | Sets value `v` for key `k`. Otherwise, returns error. |
| 9 | `n := m.Size()` | Returns the number of items in `m`. |
| 10 | `str := m.String()` | Returns `m` as a string in the format "table[k1:v1 k2:v2 ...]". |
| 11 | `cap := m.TotalCapacity()` | Returns how many slots `m` has allocated. |
| 12 | `ok := m.Drop(k)` | Removes `k` from the table. Returns whether the key had existed. |
</details>
### Determining Congruency
So, how does the core functionality compare?
Listed below is an analysis of every interface in Go's standard map.
Each is compared against what `go-cuckoo` offers, and categorized into the following groups:
- ✅ Covered: an analog exists.
- ⚠️ Partial: workaround available.
- ❌ Gap: no analog yet; addressed in [Target State](#solving-congruency).
Specifically, here we are checking for functionality.
Is there functionality that this offers which `go-cuckoo` does not?
We are checking accessibility, but not discoverability.
The latter will be considered later.
<details>
<summary>✅ <code>m := make(map[K]V)</code></summary>
The analog is `m := New()`.
</details>
<details>
<summary>⚠️ <code>m := make(map[K]V, hint)</code></summary>
This has no simple analog.
It is close to `m := New(Capacity(hint))`, but it assigns starting capacity, not expected size.
For the built-in map, these are two separate things.
- Capacity is an internal measure, used to optimize space/speed.
It is hidden from the user because it depends on the underlying implementation, which may change.
- Expected size requires the map must hold a number of items before resizing.
This is tangeable and agnostic to implementation, hence why it is given to the user.
In short, this interface defines expected size, but `Capacity()` defines capacity.
</details>
<details>
<summary>❌ <code>m := map[K]V{...}</code></summary>
This has no simple analog, the closest being:
```go
m := New[K, V]()
for k, v := range startingEntries {
m.Put(k, v)
}
```
It is idiomatic, but far less ergonomic.
</details>
<details>
<summary>✅ <code>var m map[K]V</code></summary>
The analog is `var m Table[K, V]`.
</details>
<details>
<summary>✅ <code>m[k] := v</code></summary>
The analog is `err := m.Put(k, v)`.
</details>
<details>
<summary>✅ <code>v := m[k]</code></summary>
The analog is `v := m.Find(k)`.
</details>
<details>
<summary>✅ <code>v, ok := m[k]</code></summary>
The analog is `v, ok := m.Get(k)`.
</details>
<details>
<summary>✅ <code>for k, v := range m</code></summary>
The analog is `for k, v := range m.Entries()`.
</details>
<details>
<summary>✅ <code>delete(m, k)</code></summary>
The analog is `ok := m.Drop(k)`.
</details>
<details>
<summary>❌ <code>clear(m)</code></summary>
There is no analog.
The easiest may to do this is to delete all items individually:
```go
for k := range m.Entries() {
m.Drop(k)
}
```
</details>
<details>
<summary>✅ <code>n := len(m)</code></summary>
The analog is `n := m.Size()`.
</details>
<details>
<summary>❌ <code>m2 := maps.Clone(m)</code></summary>
There is no analog.
The easiest way to do this currently is to make a new map, and manually add the items.
```go
m2 := cuckoo.Table[K, V]()
for k, v := range m.Entries() {
m2.Put(k, v)
}
```
This gets complicated by the various options available to the user.
Furthermore, any custom `EqualFunc`, `keyFunc` or `Hash` is not transferred.
</details>
<details>
<summary>❌ <code>maps.Copy(dst, src)</code></summary>
There is no analog.
The simplest way to do this is with a for-loop.
```go
for k, v := range src.Entries() {
dst.Put(k, v)
}
```
</details>
<details>
<summary>❌ <code>ok := maps.Equal(m1, m2)</code></summary>
There is no analog.
Users have to manually check the key-value pairs to determine equality.
</details>
<details>
<summary>❌ <code>ok := maps.EqualFunc(m1, m2, fn)</code></summary>
There is no analog.
Users have to manually check the key-value pairs to determine equality.
</details>
<details>
<summary>❌ <code>maps.DeleteFunc(m, fn)</code></summary>
There is no analog.
Users have to manually delete keys.
</details>
<details>
<summary>✅ <code>it2 := maps.All(m)</code></summary>
The analog is `it2 := m.Entries()`.
</details>
<details>
<summary>⚠️ <code>it := maps.Keys(m)</code></summary>
There is no simple analog.
A close neighbor is `it2 := m.Entries()`.
Users can use this in a for-loop, and pick out just the keys:
```go
for k := range m.Entries() {
// ...
}
```
</details>
<details>
<summary>⚠️ <code>it := maps.Values(m)</code></summary>
There is no simple analog.
A close neighbor is `it2 := m.Entries()`.
Users can use this in a for-loop, and pick out just the values:
```go
for _, v := range m.Entries() {
// ...
}
```
</details>
<details>
<summary>❌ <code>m := maps.Collect(seq)</code></summary>
There is no analog.
</details>
<details>
<summary>❌ <code>maps.Insert(m, seq)</code></summary>
There is no analog.
</details>
### Determining Familiarity
We can categorize all existing table functionality by each interface's familiarity:
- ✅ Idiomatic: is clear, intuitive, and easily understood.
- ❌ Non-idiomatic: is misleading; addressed in [Target State](#solving-congruency).
<details>
<summary>✅ <code>m := New(opts...)</code></summary>
Criteria:
Noun/adjective form — Go constructors use NewX where X is a noun or adjective, not a verb or past participle (NewReaderSize, not NewSized)
Names what the user provides — the suffix should hint at the distinguishing parameter (NewBufferString tells you it takes a string)
Progression is readable — the three names together should imply simple → intermediate → advanced
Not misleadingly generic — NewWith or NewConfig could mean anything
</details>
<details>
<summary><code>m := NewBy(keyFunc, opts...)</code></summary>
- Use `NewKeyed()`.
</details>
<details>
<summary><code>m := NewCustom(hashA, hashB, equalFunc, opts...)</code></summary>
- Use `NewHashed()`.
</details>
<details>
<summary>❌ <code>seq := m.Entries()</code></summary>
- Call it `All()`.
</details>
<details>
<summary><code>v := m.Find(k)</code></summary>
- Call it `m.Lookup()`. The name `m.Find` implies a search algorithm.
</details>
<details>
<summary><code>v, ok := m.Get(k)</code></summary>
</details>
<details>
<summary><code>ok := m.Has(k)</code></summary>
</details>
<details>
<summary>❌ <code>err := m.Put(k, v)</code></summary>
- Call it `Set()`.
- No built-in library consensus, but 3rd party packages prefer `Set()`.
</details>
<details>
<summary>❌ <code>n := m.Size()</code></summary>
- Call it `Len()`.
- Size is a Java idiom.
</details>
<details>
<summary>✅ <code>str := m.String()</code></summary>
</details>
<details>
<summary>❌ <code>cap := m.TotalCapacity()</code></summary>
- Remove. This is an implementation detail.
</details>
<details>
<summary>❌ <code>ok := m.Drop(k)</code></summary>
- Call it `Delete()`.
</details>
## Target State
### Solving Congruency
We should make the following changes to accomodate for congruency:
<details>
<summary><code>ok := maps.EqualFunc(m1, m2, fn)</code></summary>
We should implement a new function:
```go
func EqualFunc[K, V1, V2 any](t1 *Table[K, V1], t2 *Table[K, V2], eq func(V1, V2) bool) bool
```
This function is free, and not bound as a receiver function.
(It is called `cuckoo.Equal(t1, t2)`, not `t1.Equals(t2)`.)
The latter implies `t1` has authority, when in fact neither do.
We define equality as:
1. Neither table has a key the other doesn't.
2. Each key has the same value in each table.
Parameter `eq` determines this equality.
Custom `EqualFunc`'s complicate this, as they modulate key identity in tables.
If two tables may differ on whether two keys are different, this function might break.
So, we must assume that:
- Both tables have `EqualFunc`'s which 'agree' on the identity of the keys present in the tables.
Agreement is defined as: if two keys are distinct in one table, they are distinct in the other.
The name `EqualFunc` is already taken by `EqualFunc[K, V]`: an alias for `func(a, b K) bool`.
Inlining `EqualFunc[K, V]` would solve this problem.
We will move the documentation attached to it to `DefaultEqualFunc`.
</details>
<details>
<summary><code>ok := maps.Equal(m1, m2)</code></summary>
We should implement a new function, to conform with the standard library:
```go
func Equal[K any, V comparable](t1, t2 *Table[K, V]) bool
```
It uses the same equality check as in `EqualFunc`.
Once again, the function is free because it is symmetric.
</details>
<details>
<summary><code>maps.Insert(m, seq)</code></summary>
We should implement a new receiver for the table:
```go
func (t *Table[K, V]) Insert(seq iter.Seq2[K, V]) error
```
A receiver fits better even though `maps.Insert` is a free function, because copying it is asymmetric.
Map `dst` receives entries from map `src`.
It's only free because Go's standard map is built into the language, and so cannot have receivers.
In terms of naming, `t.Extend` is more accurate, and has precedent in [Python](docs.python.org/3/tutorial/datastructures.html#more-on-lists) and [Rust](https://doc.rust-lang.org/std/iter/trait.Extend.html).
When [adding iterator function](https://github.com/golang/go/issues/61900) to the `maps` package, the Go team chose to frame it as 'sources' and 'sinks'.
With this model, `maps.Insert` made more sense than `maps.Extend`.
Ultimately, `t.Insert()` is a better choice to be consistent with `maps`.
</details>
<details>
<summary><code>maps.Copy(dst, src)</code></summary>
We should implement a new receiver for the table:
```go
func (t *Table[K, V]) Copy(src *Table[K, V]) error
```
It's functionality should match that of `t.Insert()`.
A receiver fits better even though `maps.Copy` is a free function, 'copying' it is asymmetric: `dst` is writen into by `src`.
It is only free because Go's standard map is built into the language, and so cannot have receivers.
The name `t.Merge()` might be more accurate, but it does work because:
- `t.Copy()` matches Go's built-in `copy()`, and `io.Copy()`. The Go team used [the same logic](https://github.com/golang/go/discussions/47330#discussioncomment-1167799) to name `maps.Copy()`.
In this case, `t.Merge()` would be an outlier.
- `t.Merge()` implies some sort of conflict-resolution, when there is not.
It simply overwrites the values.
</details>
<details>
<summary><code>maps.DeleteFunc(m, fn)</code></summary>
We should implement a new receiver for the table:
```go
func (t *Table[K, V]) DeleteFunc(del func(K, V) bool)
```
It would have the same functionality as `maps.DeleteFunc`.
A free function could work here, but `t` has clear authority over `del`.
Other than being consistent with the `maps` package, `t.DeleteFunc` follows the Go convention of appending `Func` to higher-order equivalents of functions.
This trumps names like `t.DeleteIf`, which lend more to [Java](https://docs.oracle.com/javase/8/docs/api/java/util/ArrayList.html#removeIf-java.util.function.Predicate-) or [C++](https://en.cppreference.com/cpp/algorithm/remove).
The word `Delete` is also convention, tying back to the built-in `delete()`.
</details>
<details>
<summary><code>m := maps.Collect(seq)</code></summary>
We should implement a new constructor.
```go
func Collect[K comparable, V any](seq iter.Seq2[K, V]) (*Table[K, V], error)
```
It would create a `New()` table, and insert all entries in `seq`.
This reveicer only supports the standard table constructor, with comparable keys.
It is tempting to add `CollectBy` or `CollectCustom` to support all table types, but doing so would pollute the public interface.
It would be just one more line to initialize the table and then call `t.Insert` directly:
```go
t := // ...
err := t.Insert(seq)
```
</details>
<details>
<summary><code>m := map[K]V{...}</code></summary>
We should make a new constructor, because entries are generic.
So, creating an option with inialized entries doesn't work.
With the previous additions, users have a few options.
If they want to use a `New()` table, `t.Collect` matches well:
```go
t, err := cuckoo.Collect(func(yield func(K, V) bool) {
yield(key1, val1)
yield(key2, val2)
})
```
For `NewCustom()` or `NewBy()` tables, users can call `t.Insert` after initialization:
```go
t := // ...
err := t.Insert(func(yield func(K, V) bool) {
yield(key1, val1)
yield(key2, val2)
})
```
It is one more line.
But, the alternative is polluting the public interface with corresponding `*WithEntries` constuctors.
</details>
<details>
<summary><code>m := make(map[K]V, hint)</code></summary>
We should add a new option:
```go
func ExpectedSize(n int) Option
```
When fed to a table, it will allocate enough space to hold `n` entries without a resize.
</details>
<details>
<summary><code>clear(m)</code></summary>
We should implement a new receiver:
```go
func (t *Table[K, V]) Clear()
```
It will remove all entries from the table.
</details>
<details>
<summary><code>m2 := maps.Clone(m)</code></summary>
We should implement a matching function:
```go
func (t *Table[K, V]) Clone() *Table[K, V]
```
Also, it will copy the hash, equality function, and options used in the table.
</details>
<details>
<summary><code>it := maps.Keys(m)</code></summary>
We should implement a matching function:
```go
func (t *Table[K, V]) Keys() iter.Seq[K]
```
It is tempting to just have `All()`, but it returns a `Seq2`, not a `Seq`.
There is no iterator adaptor between `Seq` and `Seq2`, and will not be for the foreseeable future.
This function, while it feels superfluous, is required.
</details>
<details>
<summary><code>it := maps.Values(m)</code></summary>
We should implement a matching function:
```go
func (t *Table[K, V]) Values() iter.Seq[V]
```
For the same reason we need `Keys()`, we also need `Values()`.
</details>