move Backend interface to backend package

internal/backend/rewind_reader_test.go

@@ -0,0 +1,175 @@
+package backend
+
+import (
+	"bytes"
+	"crypto/md5"
+	"hash"
+	"io"
+	"math/rand"
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+
+	"github.com/restic/restic/internal/test"
+)
+
+func TestByteReader(t *testing.T) {
+	buf := []byte("foobar")
+	for _, hasher := range []hash.Hash{nil, md5.New()} {
+		fn := func() RewindReader {
+			return NewByteReader(buf, hasher)
+		}
+		testRewindReader(t, fn, buf)
+	}
+}
+
+func TestFileReader(t *testing.T) {
+	buf := []byte("foobar")
+
+	d := test.TempDir(t)
+	filename := filepath.Join(d, "file-reader-test")
+	err := os.WriteFile(filename, buf, 0600)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	f, err := os.Open(filename)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	defer func() {
+		err := f.Close()
+		if err != nil {
+			t.Fatal(err)
+		}
+	}()
+
+	for _, hasher := range []hash.Hash{nil, md5.New()} {
+		fn := func() RewindReader {
+			var hash []byte
+			if hasher != nil {
+				// must never fail according to interface
+				_, err := hasher.Write(buf)
+				if err != nil {
+					panic(err)
+				}
+				hash = hasher.Sum(nil)
+			}
+			rd, err := NewFileReader(f, hash)
+			if err != nil {
+				t.Fatal(err)
+			}
+			return rd
+		}
+
+		testRewindReader(t, fn, buf)
+	}
+}
+
+func testRewindReader(t *testing.T, fn func() RewindReader, data []byte) {
+	seed := time.Now().UnixNano()
+	t.Logf("seed is %d", seed)
+	rnd := rand.New(rand.NewSource(seed))
+
+	type ReaderTestFunc func(t testing.TB, r RewindReader, data []byte)
+	var tests = []ReaderTestFunc{
+		func(t testing.TB, rd RewindReader, data []byte) {
+			if rd.Length() != int64(len(data)) {
+				t.Fatalf("wrong length returned, want %d, got %d", int64(len(data)), rd.Length())
+			}
+
+			buf := make([]byte, len(data))
+			_, err := io.ReadFull(rd, buf)
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			if !bytes.Equal(buf, data) {
+				t.Fatalf("wrong data returned")
+			}
+
+			if rd.Length() != int64(len(data)) {
+				t.Fatalf("wrong length returned, want %d, got %d", int64(len(data)), rd.Length())
+			}
+
+			err = rd.Rewind()
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			if rd.Length() != int64(len(data)) {
+				t.Fatalf("wrong length returned, want %d, got %d", int64(len(data)), rd.Length())
+			}
+
+			buf2 := make([]byte, int64(len(data)))
+			_, err = io.ReadFull(rd, buf2)
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			if !bytes.Equal(buf2, data) {
+				t.Fatalf("wrong data returned")
+			}
+
+			if rd.Length() != int64(len(data)) {
+				t.Fatalf("wrong length returned, want %d, got %d", int64(len(data)), rd.Length())
+			}
+
+			if rd.Hash() != nil {
+				hasher := md5.New()
+				// must never fail according to interface
+				_, _ = hasher.Write(buf2)
+				if !bytes.Equal(rd.Hash(), hasher.Sum(nil)) {
+					t.Fatal("hash does not match data")
+				}
+			}
+		},
+		func(t testing.TB, rd RewindReader, data []byte) {
+			// read first bytes
+			buf := make([]byte, rnd.Intn(len(data)))
+			_, err := io.ReadFull(rd, buf)
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			if !bytes.Equal(buf, data[:len(buf)]) {
+				t.Fatalf("wrong data returned")
+			}
+
+			err = rd.Rewind()
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			buf2 := make([]byte, rnd.Intn(len(data)))
+			_, err = io.ReadFull(rd, buf2)
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			if !bytes.Equal(buf2, data[:len(buf2)]) {
+				t.Fatalf("wrong data returned")
+			}
+
+			// read remainder
+			buf3 := make([]byte, len(data)-len(buf2))
+			_, err = io.ReadFull(rd, buf3)
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			if !bytes.Equal(buf3, data[len(buf2):]) {
+				t.Fatalf("wrong data returned")
+			}
+		},
+	}
+
+	for _, test := range tests {
+		t.Run("", func(t *testing.T) {
+			rd := fn()
+			test(t, rd, data)
+		})
+	}
+}