[vegz] Add simple sync.Pool task.

vegz/README.md

@@ -0,0 +1,3 @@
+## vegz [runtime]
+
+В этой задаче нужно победить бенчмарк, переписав функцию сериализации в `gzip`.

vegz/encode.go

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+//go:build !solution
+
+package vegz
+
+import (
+	"compress/gzip"
+	"io"
+)
+
+func Encode(data []byte, w io.Writer) error {
+	ww := gzip.NewWriter(w)
+	defer func() { _ = ww.Close() }()
+	if _, err := ww.Write(data); err != nil {
+		return err
+	}
+	return ww.Flush()
+}

vegz/encode_test.go

@@ -0,0 +1,63 @@
+package vegz
+
+import (
+	"bytes"
+	"compress/gzip"
+	"io"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	"gitlab.com/slon/shad-go/tools/testtool"
+)
+
+func BenchmarkEncode(b *testing.B) {
+	data := []byte(
+		"New function should generally only return pointer types, " +
+			"since a pointer can be put into the return interface " +
+			"value without an allocation. " +
+			testtool.RandomName(),
+	)
+
+	b.ResetTimer()
+	b.ReportAllocs()
+	for n := 0; n < b.N; n++ {
+		require.NoError(b, Encode(data, io.Discard))
+	}
+}
+
+func TestRoundTrip(t *testing.T) {
+	testCases := []struct {
+		name string
+		in   string
+	}{
+		{name: "empty", in: ""},
+		{name: "simple", in: "A long time ago in a galaxy far, far away..."},
+		{name: "random", in: testtool.RandomName()},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			buf := new(bytes.Buffer)
+			require.NoError(t, Encode([]byte(tc.in), buf))
+
+			out, err := decode(buf.Bytes())
+			require.NoError(t, err, tc.in)
+			require.Equal(t, tc.in, string(out))
+		})
+
+	}
+}
+
+func decode(data []byte) ([]byte, error) {
+	r, err := gzip.NewReader(bytes.NewReader(data))
+	if err != nil {
+		return nil, err
+	}
+
+	buf := &bytes.Buffer{}
+	if _, err := io.Copy(buf, r); err != nil {
+		return nil, err
+	}
+
+	return buf.Bytes(), nil
+}

vegz/solution.go

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+//go:build solution
+
+package vegz
+
+import (
+	"compress/gzip"
+	"io"
+	"sync"
+)
+
+var writerPool = sync.Pool{
+	New: func() interface{} {
+		return new(gzip.Writer)
+	},
+}
+
+func Encode(data []byte, w io.Writer) error {
+	ww := writerPool.Get().(*gzip.Writer)
+	defer func() {
+		_ = ww.Close()
+		writerPool.Put(ww)
+	}()
+
+	ww.Reset(w)
+
+	if _, err := ww.Write(data); err != nil {
+		return err
+	}
+
+	return ww.Close()
+}