init

Author: nikolaydubina

.github/CODEOWNERS

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+* @nikolaydubina

.github/dependabot.yml

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+version: 2
+updates:
+  - package-ecosystem: "gomod"
+    directory: "/"
+    schedule:
+      interval: "weekly"

.github/workflows/test.yml

@@ -0,0 +1,42 @@
+name: Test
+
+on:
+  push:
+    branches: [master]
+  pull_request:
+    branches: [master]
+
+permissions: read-all
+
+jobs:
+  build:
+    name: Test
+    runs-on: ubuntu-latest
+    steps:
+      - name: get code
+        uses: actions/checkout@v4
+
+      - name: setup go
+        uses: actions/setup-go@v5
+        with:
+          go-version: ^1.22
+
+      - name: test
+        run: |
+          go install github.com/jstemmer/go-junit-report/v2@latest
+          go test -coverprofile=coverage.out -covermode=atomic -cover -json -v ./... 2>&1 | go-junit-report -set-exit-code > tests.xml
+
+      - name: fuzz
+        run: go test -list . | grep Fuzz | xargs -P 8 -I {} go test -fuzz {} -fuzztime 30s .
+
+      - name: Upload test results to Codecov
+        uses: codecov/test-results-action@v1
+        with:
+          token: ${{ secrets.CODECOV_TOKEN }}
+          files: tests.xml
+
+      - name: Upload coverage to Codecov
+        uses: codecov/codecov-action@v4.1.1
+        with:
+          token: ${{ secrets.CODECOV_TOKEN }}
+          files: coverage.out

README.md

@@ -1 +1,18 @@
-# base64-reader
+Read `base64` as if it was decoded.
+
+Likely you would need `base64.NewDecoder` instead.
+
+* zero memory copy
+* fuzz tests
+
+```bash
+$ go test -bench=. -benchmem .   
+goos: darwin
+goarch: arm64
+pkg: github.com/ndx-technologies/base64io
+cpu: Apple M3 Max
+BenchmarkBase64Reader/513B-16            1234977               963.0 ns/op          1552 B/op          6 allocs/op
+BenchmarkBase64Reader/513B_native-16     1378896               872.4 ns/op          3504 B/op          5 allocs/op
+PASS
+ok      github.com/ndx-technologies/base64io    4.123s
+```

base64_reader.go

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+package base64io
+
+import (
+	"encoding/base64"
+	"io"
+)
+
+// Base64Reader decodes base64 on fly.
+type Base64Reader struct {
+	r    io.Reader
+	d    *base64.Encoding
+	b    []byte // read buffer
+	o    []byte // output buffer
+	s, e int    // output buffer start and end
+}
+
+func NewBase64Reader(r io.Reader, d *base64.Encoding) *Base64Reader {
+	return &Base64Reader{r: r, d: d, b: make([]byte, 8), o: make([]byte, 8)}
+}
+
+func (s *Base64Reader) Read(b []byte) (int, error) {
+	if len(b) == 0 {
+		return 0, nil
+	}
+
+	if s.s < s.e {
+		if n := copy(b, s.o[s.s:s.e]); n > 0 {
+			s.s += n
+			return n, nil
+		}
+	}
+
+	n, err := s.r.Read(s.b)
+	if err != nil {
+		return 0, err
+	}
+
+	m, err := s.d.Decode(s.o, s.b[:n])
+
+	l := copy(b, s.o[:m])
+
+	if l < len(s.o) {
+		s.s, s.e = l, m
+	}
+
+	return l, err
+}

base64_reader_test.go

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+package base64io_test
+
+import (
+	"encoding/base64"
+	"fmt"
+	"io"
+	"strings"
+	"testing"
+
+	"github.com/ndx-technologies/base64io"
+)
+
+func ExampleBase64Reader() {
+	b := base64.StdEncoding.EncodeToString([]byte("Hello 🌏"))
+	r := base64io.NewBase64Reader(strings.NewReader(b), base64.StdEncoding)
+	o, _ := io.ReadAll(r)
+	fmt.Println(string(b) + " -> " + string(o))
+	// Output: SGVsbG8g8J+Mjw== -> Hello 🌏
+}
+
+func FuzzBase64Reader(f *testing.F) {
+	f.Add([]byte(nil))
+	f.Add([]byte{})
+	f.Add([]byte(" "))
+	f.Add([]byte("    asdf   "))
+	f.Add([]byte(strings.Repeat("a", 513)))
+
+	f.Fuzz(func(t *testing.T, b []byte) {
+		r := base64io.NewBase64Reader(strings.NewReader(base64.StdEncoding.EncodeToString(b)), base64.StdEncoding)
+		o, err := io.ReadAll(r)
+		if err != nil {
+			t.Error(err)
+		}
+		if string(b) != string(o) {
+			t.Errorf("expected %s, got %s", string(b), string(o))
+		}
+	})
+}
+
+func BenchmarkBase64Reader(b *testing.B) {
+	b.Run("513B", func(b *testing.B) {
+		source := strings.Repeat("a", 513)
+		s := base64.StdEncoding.EncodeToString([]byte(source))
+
+		b.ResetTimer()
+		for range b.N {
+			r := base64io.NewBase64Reader(strings.NewReader(s), base64.StdEncoding)
+			o, err := io.ReadAll(r)
+			if err != nil {
+				b.Error(err)
+			}
+			if source != string(o) {
+				b.Errorf("expected %s, got %s", source, string(o))
+			}
+		}
+	})
+
+	b.Run("513B_native", func(b *testing.B) {
+		source := strings.Repeat("a", 513)
+		s := base64.StdEncoding.EncodeToString([]byte(source))
+
+		b.ResetTimer()
+		for range b.N {
+			r := base64.NewDecoder(base64.StdEncoding, strings.NewReader(s))
+
+			o, err := io.ReadAll(r)
+			if err != nil {
+				b.Error(err)
+			}
+			if source != string(o) {
+				b.Errorf("expected %s, got %s", source, string(o))
+			}
+		}
+	})
+}

go.mod

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+module github.com/ndx-technologies/base64io
+
+go 1.23.0