feat: Initial implementation of base85 + testing + docs

.github/dependabot.yml

@@ -0,0 +1,11 @@
+version: 2
+updates:
+  - package-ecosystem: "gomod"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"

.github/workflows/codeql.yml

@@ -0,0 +1,48 @@
+name: "CodeQL"
+
+on:
+  push:
+    branches: [ "main" ]
+  pull_request:
+
+jobs:
+  analyze:
+    name: Analyze (${{ matrix.language }})
+    runs-on: ${{ (matrix.language == 'swift' && 'macos-latest') || 'ubuntu-latest' }}
+    permissions:
+      security-events: write
+      packages: read
+      actions: read
+      contents: read
+
+    strategy:
+      fail-fast: false
+      matrix:
+        language: [ 'go' ]
+
+    steps:
+    - name: Checkout repository
+      uses: actions/checkout@v6
+
+    - name: Set up Go
+      uses: actions/setup-go@v6
+      with:
+        cache: false
+        go-version-file: go.mod
+      if: ${{ matrix.language == 'go' }}
+
+    - name: Initialize CodeQL
+      uses: github/codeql-action/init@v4
+      with:
+        languages: ${{ matrix.language }}
+      timeout-minutes: 10
+
+    - name: Autobuild (${{ matrix.language }})
+      uses: github/codeql-action/autobuild@v4
+      timeout-minutes: 10
+
+    - name: Perform CodeQL Analysis (${{ matrix.language }})
+      uses: github/codeql-action/analyze@v4
+      with:
+        category: "/language:${{matrix.language}}"
+      timeout-minutes: 10

.github/workflows/tests-main.yml

@@ -0,0 +1,13 @@
+name: Tests - Main Push
+
+on:
+  push:
+    branches: [ main ]
+
+permissions:
+  contents: read
+
+jobs:
+  call-reusable:
+    uses: ./.github/workflows/tests-workflow.yml
+

.github/workflows/tests-pr.yml

@@ -0,0 +1,12 @@
+name: Tests - Pull Request
+
+on:
+  pull_request:
+
+permissions:
+  contents: read
+
+jobs:
+  call-reusable:
+    uses: ./.github/workflows/tests-workflow.yml
+

.github/workflows/tests-workflow.yml

@@ -0,0 +1,58 @@
+name: Tests
+
+on:
+  workflow_call:
+
+permissions:
+  contents: read
+
+jobs:
+  lint-and-tidy:
+    name: Verify Linting
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+
+      - name: Set up Go
+        uses: actions/setup-go@v6
+        with:
+          go-version: "1.25"
+
+      - name: Set up golangci-lint
+        run: |
+          curl -sSfL https://raw.githubusercontent.com/golangci/golangci-lint/v2.7.1/install.sh | sh -s -- -b $(go env GOPATH)/bin v2.7.1
+
+      - name: Run lint check
+        run: make lint
+
+      - name: Run tidy check
+        run: |
+          go mod tidy
+          # Fail if go.mod or go.sum changed
+          git diff --exit-code go.mod go.sum
+
+  test:
+    name: Verify Unit Tests
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        go:
+        - '1.25'
+        - '1.24'
+        - '1.23'
+        - '1.22'
+        - '1.21'
+        - '1.20'
+        - '1.19'
+        - '1.18'
+    steps:
+      - uses: actions/checkout@v6
+
+      - name: Set up Go ${{ matrix.go }}
+        uses: actions/setup-go@v6
+        with:
+          go-version: ${{ matrix.go }}
+
+      - name: Run unit tests
+        run: make test
+

.golangci.yml

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+version: 2
+
+linters:
+  enable:
+    - asasalint
+    - asciicheck
+    - bidichk
+    - containedctx
+    - contextcheck
+    - decorder
+    - durationcheck
+    - errcheck
+    - errorlint
+    - exptostd
+    - fatcontext
+    - forbidigo
+    - gocheckcompilerdirectives
+    - gochecksumtype
+    - goconst
+    - godoclint
+    - gosmopolitan
+    - grouper
+    - iface
+    - importas
+    - mirror
+    - misspell
+    - musttag
+    - nilerr
+    - nilnil
+    - perfsprint
+    - prealloc
+    - reassign
+    - sloglint
+    - testifylint
+    - thelper
+    - unconvert
+    - wastedassign
+    - whitespace
+  settings:
+    goconst:
+      min-len: 4
+      min-occurrences: 4
+
+formatters:
+  enable:
+    - gofmt
+    - goimports
+
+run:
+  timeout: 600s

Makefile

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+export GO111MODULE=on
+
+.PHONY: default test test-cover test-fuzz bench lint
+
+
+test:
+	go test -race -cover ./...
+
+test-cover:
+	go test -race -coverprofile=test.out ./... && go tool cover --html=test.out
+
+test-fuzz:
+	go test -fuzz='^FuzzEncode$$' -fuzztime=2m ./base85/...
+	go test -fuzz='^FuzzDecode$$' -fuzztime=2m ./base85/...
+	go test -fuzz='^FuzzEncodeWithPadding$$' -fuzztime=2m ./base85/...
+	go test -fuzz='^FuzzDecodeWithPadding$$' -fuzztime=2m ./base85/...
+	go test -fuzz='^FuzzStreamRoundTrip$$' -fuzztime=2m ./base85/...
+	go test -fuzz='^FuzzStreamRoundTripWithPadding$$' -fuzztime=2m ./base85/...
+
+bench:
+	go test --benchmem -benchtime=10s -bench='Benchmark.*' -run='^$$' ./...
+
+lint:
+	golangci-lint run --timeout=600s && go vet ./...
+

README.md

@@ -1,2 +1,53 @@
 # encoding
-Encoding utilities for data processing and storage
+
+Lightweight encoding packages for niche use cases not covered by Go's standard library. These packages are useful when you need compact encodings with specific character set requirements.
+
+The API closely mirrors Go's `encoding/base64` and related packages, making it easy to transition to standard implementations if they become available. Packages will be deprecated and removed if equivalent functionality is added to the standard library.
+
+## Installation
+
+```bash
+go get github.com/go-analyze/encoding@latest
+```
+
+## base85
+
+The standard library's `encoding/ascii85` package only supports the Adobe/btoa variant with a fixed alphabet. This package provides base85 encoding with support for custom alphabets via `NewEncoding()`, following the same pattern as `encoding/base64`.
+
+### RFC1924
+
+RFC1924 defines a base85 encoding designed for compact representation of IPv6 addresses. It uses an 85-character alphabet consisting of `0-9`, `A-Z`, `a-z`, and 23 punctuation symbols, deliberately excluding characters that could cause parsing issues in various contexts (quotes, comma, period, slash, colon, brackets, and backslash).
+
+```go
+package main
+
+import (
+	"fmt"
+
+	"github.com/go-analyze/encoding/base85"
+)
+
+func main() {
+	data := []byte("Hello, World!")
+
+	// Encode
+	encoded := base85.RFC1924.EncodeToString(data)
+	fmt.Println(encoded) // NM&qnZ!92JZ*pv8Ap
+
+	// Decode
+	decoded, err := base85.RFC1924.DecodeString(encoded)
+	if err != nil {
+		panic(err)
+	}
+	fmt.Println(string(decoded)) // Hello, World!
+}
+```
+
+### Custom Alphabets
+
+Create encodings with custom 85-character alphabets:
+
+```go
+enc := base85.NewEncoding("0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz!#$%&()*+-;<=>?@^_`{|}~")
+encoded := enc.EncodeToString(data)
+```

base85/bench_test.go

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+package base85
+
+import (
+	"encoding/ascii85"
+	"testing"
+)
+
+var benchData = []byte("The quick brown fox jumps over the lazy dog. 0123456789!@#$%^&*()")
+
+func BenchmarkEncodeBase85(b *testing.B) {
+	dst := make([]byte, RFC1924.EncodedLen(len(benchData)))
+	b.ResetTimer()
+
+	for i := 0; i < b.N; i++ {
+		RFC1924.Encode(dst, benchData)
+	}
+}
+
+func BenchmarkDecodeBase85(b *testing.B) {
+	encoded := RFC1924.EncodeToString(benchData)
+	src := []byte(encoded)
+	dst := make([]byte, RFC1924.DecodedLen(len(src)))
+	b.ResetTimer()
+
+	for i := 0; i < b.N; i++ {
+		_, _ = RFC1924.Decode(dst, src)
+	}
+}
+
+func BenchmarkEncodeAscii85(b *testing.B) {
+	dst := make([]byte, ascii85.MaxEncodedLen(len(benchData)))
+	b.ResetTimer()
+
+	for i := 0; i < b.N; i++ {
+		ascii85.Encode(dst, benchData)
+	}
+}
+
+func BenchmarkDecodeAscii85(b *testing.B) {
+	src := make([]byte, ascii85.MaxEncodedLen(len(benchData)))
+	n := ascii85.Encode(src, benchData)
+	src = src[:n]
+	dst := make([]byte, len(benchData))
+	b.ResetTimer()
+
+	for i := 0; i < b.N; i++ {
+		_, _, _ = ascii85.Decode(dst, src, true)
+	}
+}