first, most simple version

.gitattributes

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+*	-text

.github/dependabot.yml

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+# To get started with Dependabot version updates, you'll need to specify which
+# package ecosystems to update and where the package manifests are located.
+# Please see the documentation for all configuration options:
+# https://docs.github.com/github/administering-a-repository/configuration-options-for-dependency-updates
+
+version: 2
+updates:
+  - package-ecosystem: "github-actions" # See documentation for possible values
+    directory: "/" # Location of package manifests
+    schedule:
+      interval: "weekly"

.github/workflows/go.yml

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+name: Go
+
+on: [push]
+
+env:
+  GO_VERSION: '>=1.21.0'
+
+jobs:
+
+  build:
+    name: Build
+    runs-on: ${{ matrix.os }}
+
+    strategy:
+      matrix:
+        os: [ ubuntu-latest, macos-latest, windows-latest ]
+    steps:
+
+    - uses: actions/checkout@v4
+
+    - uses: actions/setup-go@v5
+      with:
+        go-version: ${{ env.GO_VERSION }}
+
+    - run: go test
+
+    - run: go build
+
+# based on: github.com/koron-go/_skeleton/.github/workflows/go.yml

.gitignore

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+*~
+default.pgo
+tags
+tmp/

LICENSE

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+The MIT License (MIT)
+
+Copyright (c) 2024 MURAOKA Taro <[email protected]>
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.

Makefile

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+TEST_PACKAGE ?= ./...
+
+.PHONY: build
+build:
+	go build -gcflags '-e' ./...
+
+.PHONY: test
+test:
+	go test $(TEST_PACKAGE)
+
+.PHONY: bench
+bench:
+	go test -bench $(TEST_PACKAGE)
+
+.PHONY: tags
+tags:
+	gotags -f tags -R .
+
+.PHONY: cover
+cover:
+	mkdir -p tmp
+	go test -coverprofile tmp/_cover.out $(TEST_PACKAGE)
+	go tool cover -html tmp/_cover.out -o tmp/cover.html
+
+.PHONY: checkall
+checkall: vet staticcheck
+
+.PHONY: vet
+vet:
+	go vet $(TEST_PACKAGE)
+
+.PHONY: staticcheck
+staticcheck:
+	staticcheck $(TEST_PACKAGE)
+
+.PHONY: clean
+clean:
+	go clean
+	rm -f tags
+	rm -f tmp/_cover.out tmp/cover.html
+
+# based on: github.com/koron-go/_skeleton/Makefile

README.md

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+# koron-go/fifo
+
+[![PkgGoDev](https://pkg.go.dev/badge/github.com/koron-go/fifo)](https://pkg.go.dev/github.com/koron-go/fifo)
+[![Actions/Go](https://github.com/koron-go/fifo/workflows/Go/badge.svg)](https://github.com/koron-go/fifo/actions?query=workflow%3AGo)
+[![Go Report Card](https://goreportcard.com/badge/github.com/koron-go/fifo)](https://goreportcard.com/report/github.com/koron-go/fifo)
+
+A simple generic FIFO queue.

fifo.go

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+/*
+Package fifo provides simple FIFO (queue) implementation.
+*/
+package fifo
+
+type entry[T any] struct {
+	value T
+	prev  *entry[T]
+}
+
+// FIFO is a simple implementation of FIFO queue
+type FIFO[T any] struct {
+	head *entry[T]
+	tail *entry[T]
+	len  int
+}
+
+// Len gets a length of FIFO queue.
+func (fifo FIFO[T]) Len() int {
+	return fifo.len
+}
+
+// Insert inserts a value into FIFO queue.
+func (fifo *FIFO[T]) Insert(v T) {
+	item := &entry[T]{value: v}
+	if fifo.head != nil {
+		fifo.head.prev = item
+	} else {
+		fifo.tail = item
+	}
+	fifo.head = item
+	fifo.len++
+}
+
+// Evict evicts the last value from FIFO queue.
+func (fifo *FIFO[T]) Evict() (T, bool) {
+	if fifo.tail == nil {
+		var zero T
+		return zero, false
+	}
+	v := fifo.tail.value
+	fifo.tail = fifo.tail.prev
+	if fifo.tail == nil {
+		fifo.head = nil
+	}
+	fifo.len--
+	return v, true
+}

fifo_test.go

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+package fifo_test
+
+import (
+	"testing"
+
+	"github.com/koron-go/fifo"
+)
+
+func TestFIFO(t *testing.T) {
+	var fifo fifo.FIFO[int]
+	if d := fifo.Len(); d != 0 {
+		t.Fatalf("fifo length is not zero: got=%d", d)
+	}
+
+	// Insert
+	fifo.Insert(1)
+	fifo.Insert(2)
+	fifo.Insert(3)
+	if d := fifo.Len(); d != 3 {
+		t.Fatalf("fifo length is not 3: got=%d", d)
+	}
+	fifo.Insert(4)
+	fifo.Insert(5)
+	if d := fifo.Len(); d != 5 {
+		t.Fatalf("fifo length is not 5: got=%d", d)
+	}
+
+	// Evict
+	if v, ok := fifo.Evict(); !ok || v != 1 {
+		t.Fatalf("failed to evict want=1: ok=%t got=%d", ok, v)
+	}
+	if d := fifo.Len(); d != 4 {
+		t.Fatalf("fifo length is not 4: got=%d", d)
+	}
+	if v, ok := fifo.Evict(); !ok || v != 2 {
+		t.Fatalf("failed to evict want=2: ok=%t got=%d", ok, v)
+	}
+	if v, ok := fifo.Evict(); !ok || v != 3 {
+		t.Fatalf("failed to evict want=3: ok=%t got=%d", ok, v)
+	}
+	if v, ok := fifo.Evict(); !ok || v != 4 {
+		t.Fatalf("failed to evict want=4: ok=%t got=%d", ok, v)
+	}
+	if d := fifo.Len(); d != 1 {
+		t.Fatalf("fifo length is not 1: got=%d", d)
+	}
+	if v, ok := fifo.Evict(); !ok || v != 5 {
+		t.Fatalf("failed to evict want=5: ok=%t got=%d", ok, v)
+	}
+	if d := fifo.Len(); d != 0 {
+		t.Fatalf("fifo length is not 0: got=%d", d)
+	}
+
+	// Evict from empty FIFO queue.
+	if v, ok := fifo.Evict(); ok || v != 0 {
+		t.Fatalf("unexpectedly a value evicted from empty FIFO queue: ok=%t got=%d", ok, v)
+	}
+
+	// Insert and Evict again
+	fifo.Insert(6)
+	fifo.Insert(7)
+	fifo.Insert(8)
+	if d := fifo.Len(); d != 3 {
+		t.Fatalf("fifo length is not 3: got=%d", d)
+	}
+	if v, ok := fifo.Evict(); !ok || v != 6 {
+		t.Fatalf("failed to evict want=6: ok=%t got=%d", ok, v)
+	}
+	if v, ok := fifo.Evict(); !ok || v != 7 {
+		t.Fatalf("failed to evict want=7: ok=%t got=%d", ok, v)
+	}
+	if v, ok := fifo.Evict(); !ok || v != 8 {
+		t.Fatalf("failed to evict want=8: ok=%t got=%d", ok, v)
+	}
+	if d := fifo.Len(); d != 0 {
+		t.Fatalf("fifo length is not 0: got=%d", d)
+	}
+}

go.mod

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+module github.com/koron-go/fifo
+
+go 1.22

rangefunc.go

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+//go:build goexperiment.rangefunc
+
+package fifo
+
+import "iter"
+
+// Seq returns iter.Seq[T] to enumerate items in FIFO queue.
+func (fifo *FIFO[T]) Seq() iter.Seq[T] {
+	return func(yield func(T) bool) {
+		for p := fifo.tail; p != nil; p = p.prev {
+			if !yield(p.value) {
+				break
+			}
+		}
+	}
+}

rangefunc_test.go

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+//go:build goexperiment.rangefunc
+
+package fifo_test
+
+import (
+	"testing"
+
+	"github.com/koron-go/fifo"
+)
+
+func TestFIFO_Seq(t *testing.T) {
+	var fifo fifo.FIFO[int]
+	fifo.Insert(1)
+	fifo.Insert(2)
+	fifo.Insert(3)
+	fifo.Insert(4)
+	fifo.Insert(5)
+	wants := []int{1, 2, 3, 4, 5}
+	for got := range fifo.Seq() {
+		if len(wants) == 0 {
+			t.Fatalf("wants exhausted: got=%d", got)
+		}
+		want := wants[0]
+		wants = wants[1:]
+		if got != want {
+			t.Fatalf("unexpected value: want=%d got=%d", want, got)
+		}
+	}
+	if len(wants) != 0 {
+		t.Fatalf("wants remained: %+v", wants)
+	}
+	if d := fifo.Len(); d != 5 {
+		t.Fatalf("fifo length is not 5: got=%d", d)
+	}
+}
+
+func TestFIFO_SeqBreak(t *testing.T) {
+	var fifo fifo.FIFO[int]
+	fifo.Insert(1)
+	fifo.Insert(2)
+	fifo.Insert(3)
+	fifo.Insert(4)
+	fifo.Insert(5)
+
+	wants := []int{1, 2, 3}
+	for got := range fifo.Seq() {
+		if len(wants) == 0 {
+			break
+		}
+		want := wants[0]
+		wants = wants[1:]
+		if got != want {
+			t.Fatalf("unexpected value: want=%d got=%d", want, got)
+		}
+	}
+	if len(wants) != 0 {
+		t.Fatalf("wants remained: %+v", wants)
+	}
+	if d := fifo.Len(); d != 5 {
+		t.Fatalf("fifo length is not 5: got=%d", d)
+	}
+}

staticcheck.conf

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+# vim:set ft=toml:
+
+checks = ["all"]
+
+# based on: github.com/koron-go/_skeleton/staticcheck.conf