src/dedo.go: Introduce SnapshotI type

2 files changed, 96 insertions, 81 deletions

diff --git a/src/dedo.go b/src/dedo.go
index 9f64693..c0aecaf 100644
--- a/src/dedo.go
+++ b/src/dedo.go
@@ -127,13 +127,20 @@ type ITx interface{
 	OnCommit(func())
 
 	WriteTo(io.Writer) (int64, error)
+}
+
+type SnapshotI interface{
+	Bucket([]byte) *Bucket
+
+	WriteTo(io.Writer) (int64, error)
+	ForEach(func([]byte, *Bucket) error) error
 
 	Check() <-chan error
 }
 
 type IDedo interface{
 	Close() error
-	View  (func(tx ITx) error) error
+	View  (func(tx SnapshotI) error) error
 	Update(func(tx ITx) error) error
 	Path() string
 }
@@ -1743,7 +1750,7 @@ func (m *InMemory) Update(fn func(ITx) error) error {
 	return err
 }
 
-func (m *InMemory) View(func(ITx) error) error {
+func (m *InMemory) View(func(SnapshotI) error) error {
 	return nil
 }
 
@@ -2109,7 +2116,7 @@ func (db *DB) Update(fn func(ITx) error) error {
 /// the DB.View() method.
 ///
 /// Attempting to manually rollback within the function will cause a panic.
-func (db *DB) View(fn func(ITx) error) error {
+func (db *DB) View(fn func(SnapshotI) error) error {
 	t, err := db.begin(false)
 	if err != nil {
 		return err
@@ -3967,9 +3974,9 @@ func setGetopt(args argsT, w io.Writer) (argsT, bool) {
 }
 
 func checkExec(args argsT, db IDedo, _r io.Reader, _w io.Writer) error {
-	return db.View(func(tx ITx) error {
+	return db.View(func(snapshot SnapshotI) error {
 		var errs error
-		for err := range tx.Check() {
+		for err := range snapshot.Check() {
 			errs = g.WrapErrors(errs, err)
 		}
 		return errs
@@ -3977,8 +3984,8 @@ func checkExec(args argsT, db IDedo, _r io.Reader, _w io.Writer) error {
 }
 
 func getExec(args argsT, db IDedo, r io.Reader, w io.Writer) error {
-	return db.View(func(tx ITx) error {
-		bucket := tx.Bucket(args.bucket)
+	return db.View(func(snapshot SnapshotI) error {
+		bucket := snapshot.Bucket(args.bucket)
 		if bucket == nil {
 			return ErrBucketNotFound
 		}
@@ -4016,9 +4023,9 @@ func rmExec(args argsT, db IDedo, r io.Reader, w io.Writer) error {
 }
 
 func listExec(args argsT, db IDedo, r io.Reader, w io.Writer) error {
-	return db.View(func(tx ITx) error {
+	return db.View(func(snapshot SnapshotI) error {
 		if len(args.bucket) == 0 {
-			return tx.ForEach(func(
+			return snapshot.ForEach(func(
 				name []byte,
 				bucket *Bucket,
 			) error {
@@ -4027,7 +4034,7 @@ func listExec(args argsT, db IDedo, r io.Reader, w io.Writer) error {
 			})
 		}
 
-		bucket := tx.Bucket(args.bucket)
+		bucket := snapshot.Bucket(args.bucket)
 		if bucket == nil {
 			return ErrBucketNotFound
 		}
diff --git a/tests/dedo.go b/tests/dedo.go
index 7dba449..b5ed229 100644
--- a/tests/dedo.go
+++ b/tests/dedo.go
@@ -753,8 +753,8 @@ func TestBucket_Put_Large(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	err = db.View(func(tx ITx) error {
-		b := tx.Bucket([]byte("widgets"))
+	err = db.View(func(snapshot SnapshotI) error {
+		b := snapshot.Bucket([]byte("widgets"))
 		for i := 1; i < count; i++ {
 			value := b.Get([]byte(strings.Repeat("0", i*factor)))
 			expected := []byte(strings.Repeat(
@@ -884,8 +884,8 @@ func TestBucket_Put_ReadOnly(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	err = db.View(func(tx ITx) error {
-		b := tx.Bucket([]byte("widgets"))
+	err = db.View(func(snapshot SnapshotI) error {
+		b := snapshot.Bucket([]byte("widgets"))
 		err := b.Put([]byte("foo"), []byte("bar"))
 		if err != ErrTxNotWritable {
 			t.Fatalf("unexpected error: %s", err)
@@ -974,8 +974,8 @@ func TestBucket_Delete_Large(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	err = db.View(func(tx ITx) error {
-		b := tx.Bucket([]byte("widgets"))
+	err = db.View(func(snapshot SnapshotI) error {
+		b := snapshot.Bucket([]byte("widgets"))
 		for i := 0; i < 100; i++ {
 			v := b.Get([]byte(strconv.Itoa(i)))
 			if v != nil {
@@ -1128,8 +1128,8 @@ func TestBucket_Nested(t *testing.T) {
 	db.MustCheck()
 
 	// Verify.
-	err = db.View(func(tx ITx) error {
-		b := tx.Bucket([]byte("widgets"))
+	err = db.View(func(snapshot SnapshotI) error {
+		b := snapshot.Bucket([]byte("widgets"))
 		v := b.Bucket([]byte("foo")).Get([]byte("baz"))
 		if !bytes.Equal(v, []byte("yyyy")) {
 			t.Fatalf("unexpected value: %v", v)
@@ -1201,8 +1201,8 @@ func TestBucket_Delete_ReadOnly(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	err = db.View(func(tx ITx) error {
-		err := tx.Bucket([]byte("widgets")).Delete([]byte("foo"))
+	err = db.View(func(snapshot SnapshotI) error {
+		err := snapshot.Bucket([]byte("widgets")).Delete([]byte("foo"))
 		if err != ErrTxNotWritable {
 			t.Fatalf("unexpected error: %s", err)
 		}
@@ -1346,8 +1346,8 @@ func TestBucket_DeleteBucket_Nested2(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	err = db.View(func(tx ITx) error {
-		if tx.Bucket([]byte("widgets")) != nil {
+	err = db.View(func(snapshot SnapshotI) error {
+		if snapshot.Bucket([]byte("widgets")) != nil {
 			t.Fatal("expected bucket to be deleted")
 		}
 		return nil
@@ -1604,8 +1604,8 @@ func TestBucket_NextSequence_ReadOnly(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	err = db.View(func(tx ITx) error {
-		_, err := tx.Bucket([]byte("widgets")).NextSequence()
+	err = db.View(func(snapshot SnapshotI) error {
+		_, err := snapshot.Bucket([]byte("widgets")).NextSequence()
 		if err != ErrTxNotWritable {
 			t.Fatalf("unexpected error: %s", err)
 		}
@@ -1915,10 +1915,10 @@ func TestBucket_Put_Single(t *testing.T) {
 			const errmsg = "value mismatch [run %d] (%d of %d):\n" +
 				"key: %x\ngot: %x\nexp: %x"
 			// Verify all key/values so far.
-			err = db.View(func(tx ITx) error {
+			err = db.View(func(snapshot SnapshotI) error {
 				i := 0
 				for k, v := range m {
-					value := tx.Bucket(
+					value := snapshot.Bucket(
 						[]byte("widgets"),
 					).Get([]byte(k))
 					if !bytes.Equal(value, v) {
@@ -1991,8 +1991,8 @@ func TestBucket_Put_Multiple(t *testing.T) {
 		}
 
 		// Verify all items exist.
-		err = db.View(func(tx ITx) error {
-			b := tx.Bucket([]byte("widgets"))
+		err = db.View(func(snapshot SnapshotI) error {
+			b := snapshot.Bucket([]byte("widgets"))
 			for _, item := range items {
 				value := b.Get(item.Key)
 				if !bytes.Equal(item.Value, value) {
@@ -2070,8 +2070,8 @@ func TestBucket_Delete_Quick(t *testing.T) {
 		}
 
 		// Anything before our deletion index should be nil.
-		err = db.View(func(tx ITx) error {
-			err := tx.Bucket(
+		err = db.View(func(snapshot SnapshotI) error {
+			err := snapshot.Bucket(
 				[]byte("widgets"),
 			).ForEach(func(k, v []byte) error {
 				t.Fatalf(
@@ -2126,8 +2126,8 @@ func ExampleBucket_Put() {
 	}
 
 	// Read value back in a different read-only transaction.
-	err = db.View(func(tx ITx) error {
-		value := tx.Bucket([]byte("widgets")).Get([]byte("foo"))
+	err = db.View(func(snapshot SnapshotI) error {
+		value := snapshot.Bucket([]byte("widgets")).Get([]byte("foo"))
 		fmt.Printf("The value of 'foo' is: %s\n", value)
 		return nil
 	})
@@ -2186,8 +2186,8 @@ func ExampleBucket_Delete() {
 	}
 
 	// Retrieve the key again.
-	err = db.View(func(tx ITx) error {
-		value := tx.Bucket([]byte("widgets")).Get([]byte("foo"))
+	err = db.View(func(snapshot SnapshotI) error {
+		value := snapshot.Bucket([]byte("widgets")).Get([]byte("foo"))
 		if value == nil {
 			fmt.Printf("The value of 'foo' is now: nil\n")
 		}
@@ -2303,8 +2303,8 @@ func TestCursor_Seek(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	err = db.View(func(tx ITx) error {
-		c := tx.Bucket([]byte("widgets")).Cursor()
+	err = db.View(func(snapshot SnapshotI) error {
+		c := snapshot.Bucket([]byte("widgets")).Cursor()
 
 		// Exact match should go to the key.
 		k, v := c.Seek([]byte("bar"))
@@ -2449,8 +2449,8 @@ func TestCursor_Seek_Large(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	err = db.View(func(tx ITx) error {
-		c := tx.Bucket([]byte("widgets")).Cursor()
+	err = db.View(func(snapshot SnapshotI) error {
+		c := snapshot.Bucket([]byte("widgets")).Cursor()
 		for i := 0; i < count; i++ {
 			seek := make([]byte, 8)
 			binary.BigEndian.PutUint64(seek, uint64(i))
@@ -2501,8 +2501,8 @@ func TestCursor_EmptyBucket(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	err = db.View(func(tx ITx) error {
-		c := tx.Bucket([]byte("widgets")).Cursor()
+	err = db.View(func(snapshot SnapshotI) error {
+		c := snapshot.Bucket([]byte("widgets")).Cursor()
 		k, v := c.First()
 		if k != nil {
 			t.Fatalf("unexpected key: %v", k)
@@ -2531,8 +2531,8 @@ func TestCursor_EmptyBucketReverse(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	err = db.View(func(tx ITx) error {
-		c := tx.Bucket([]byte("widgets")).Cursor()
+	err = db.View(func(snapshot SnapshotI) error {
+		c := snapshot.Bucket([]byte("widgets")).Cursor()
 		k, v := c.Last()
 		if k != nil {
 			t.Fatalf("unexpected key: %v", k)
@@ -3003,9 +3003,9 @@ func TestCursor_QuickCheck_BucketsOnly(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	err = db.View(func(tx ITx) error {
+	err = db.View(func(snapshot SnapshotI) error {
 		names := []string{}
-		c := tx.Bucket([]byte("widgets")).Cursor()
+		c := snapshot.Bucket([]byte("widgets")).Cursor()
 		for k, v := c.First(); k != nil; k, v = c.Next() {
 			names = append(names, string(k))
 			if v != nil {
@@ -3057,9 +3057,9 @@ func TestCursor_QuickCheck_BucketsOnly_Reverse(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	err = db.View(func(tx ITx) error {
+	err = db.View(func(snapshot SnapshotI) error {
 		names := []string{}
-		c := tx.Bucket([]byte("widgets")).Cursor()
+		c := snapshot.Bucket([]byte("widgets")).Cursor()
 		for k, v := c.Last(); k != nil; k, v = c.Prev() {
 			names = append(names, string(k))
 			if v != nil {
@@ -3494,7 +3494,9 @@ func TestOpen_Check(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	err = db.View(func(tx ITx) error { return <-tx.Check() })
+	err = db.View(func(snapshot SnapshotI) error {
+		return <-snapshot.Check()
+	})
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -3509,7 +3511,9 @@ func TestOpen_Check(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	err = db.View(func(tx ITx) error { return <-tx.Check() })
+	err = db.View(func(snapshot SnapshotI) error {
+		return <-snapshot.Check()
+	})
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -3753,8 +3757,8 @@ func TestDB_Update(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	err = db.View(func(tx ITx) error {
-		b := tx.Bucket([]byte("widgets"))
+	err = db.View(func(snapshot SnapshotI) error {
+		b := snapshot.Bucket([]byte("widgets"))
 		v := b.Get([]byte("foo"))
 		if v != nil {
 			t.Fatalf("expected nil value, got: %v", v)
@@ -3848,7 +3852,7 @@ func TestDB_View_Error(t *testing.T) {
 	defer db.MustClose()
 	defer os.Remove(db.Path())
 
-	err := db.View(func(tx ITx) error {
+	err := db.View(func(snapshot SnapshotI) error {
 		return errors.New("xxx")
 	})
 	if err == nil || err.Error() != "xxx" {
@@ -3883,8 +3887,8 @@ func TestDB_View_Panic(t *testing.T) {
 			}
 		}()
 
-		err := db.View(func(tx ITx) error {
-			if tx.Bucket([]byte("widgets")) == nil {
+		err := db.View(func(snapshot SnapshotI) error {
+			if snapshot.Bucket([]byte("widgets")) == nil {
 				t.Fatal("expected bucket")
 			}
 			panic("omg")
@@ -3895,8 +3899,8 @@ func TestDB_View_Panic(t *testing.T) {
 	}()
 
 	// Verify that we can still use read transactions.
-	err = db.View(func(tx ITx) error {
-		if tx.Bucket([]byte("widgets")) == nil {
+	err = db.View(func(snapshot SnapshotI) error {
+		if snapshot.Bucket([]byte("widgets")) == nil {
 			t.Fatal("expected bucket")
 		}
 		return nil
@@ -4034,8 +4038,8 @@ func TestDB_Batch(t *testing.T) {
 	}
 
 	// Ensure data is correct.
-	err = db.View(func(tx ITx) error {
-		b := tx.Bucket([]byte("widgets"))
+	err = db.View(func(snapshot SnapshotI) error {
+		b := snapshot.Bucket([]byte("widgets"))
 		for i := 0; i < n; i++ {
 			v := b.Get(u64tob(uint64(i)))
 			if v == nil {
@@ -4139,8 +4143,8 @@ func TestDB_BatchFull(t *testing.T) {
 	}
 
 	// Ensure data is correct.
-	err = db.View(func(tx ITx) error {
-		b := tx.Bucket([]byte("widgets"))
+	err = db.View(func(snapshot SnapshotI) error {
+		b := snapshot.Bucket([]byte("widgets"))
 		for i := 1; i <= size; i++ {
 			v := b.Get(u64tob(uint64(i)))
 			if v == nil {
@@ -4195,8 +4199,8 @@ func TestDB_BatchTime(t *testing.T) {
 	}
 
 	// Ensure data is correct.
-	err = db.View(func(tx ITx) error {
-		b := tx.Bucket([]byte("widgets"))
+	err = db.View(func(snapshot SnapshotI) error {
+		b := snapshot.Bucket([]byte("widgets"))
 		for i := 1; i <= size; i++ {
 			if v := b.Get(u64tob(uint64(i))); v == nil {
 				t.Errorf("key not found: %d", i)
@@ -4236,8 +4240,8 @@ func ExampleDB_Update() {
 	}
 
 	// Read the value back from a separate read-only transaction.
-	err = db.View(func(tx ITx) error {
-		value := tx.Bucket([]byte("widgets")).Get([]byte("foo"))
+	err = db.View(func(snapshot SnapshotI) error {
+		value := snapshot.Bucket([]byte("widgets")).Get([]byte("foo"))
 		fmt.Printf("The value of 'foo' is: %s\n", value)
 		return nil
 	})
@@ -4287,8 +4291,8 @@ func ExampleDB_View() {
 	}
 
 	// Access data from within a read-only transactional block.
-	err = db.View(func(tx ITx) error {
-		v := tx.Bucket([]byte("people")).Get([]byte("john"))
+	err = db.View(func(snapshot SnapshotI) error {
+		v := snapshot.Bucket([]byte("people")).Get([]byte("john"))
 		fmt.Printf("John's last name is %s.\n", v)
 		return nil
 	})
@@ -4671,8 +4675,8 @@ func (db *WDB) MustCheck() {
 // CopyTempFile copies a database to a temporary file.
 func (db *WDB) CopyTempFile() {
 	path := tempfile()
-	err := db.View(func(itx ITx) error {
-		tx := itx.(*Tx)
+	err := db.View(func(snapshot SnapshotI) error {
+		tx := snapshot.(*Tx)
 		return tx.copyFile(path, 0600)
 	})
 	if err != nil {
@@ -5902,14 +5906,15 @@ func TestTx_Cursor(t *testing.T) {
 	}
 }
 
+/*
 // Ensure that creating a bucket with a read-only transaction returns an error.
 func TestTx_CreateBucket_ErrTxNotWritable(t *testing.T) {
 	db := MustOpenDB()
 	defer db.MustClose()
 	defer os.Remove(db.Path())
 
-	err := db.View(func(tx ITx) error {
-		_, err := tx.CreateBucket([]byte("foo"))
+	err := db.View(func(snapshot SnapshotI) error {
+		_, err := snapshot.CreateBucket([]byte("foo"))
 		if err != ErrTxNotWritable {
 			t.Fatalf("unexpected error: %s", err)
 		}
@@ -5920,6 +5925,7 @@ func TestTx_CreateBucket_ErrTxNotWritable(t *testing.T) {
 		t.Fatal(err)
 	}
 }
+*/
 
 // Ensure that creating a bucket on a closed transaction returns an error.
 func TestTx_CreateBucket_ErrTxClosed(t *testing.T) {
@@ -6016,8 +6022,8 @@ func TestTx_CreateBucket(t *testing.T) {
 	}
 
 	// Read the bucket through a separate transaction.
-	err = db.View(func(tx ITx) error {
-		if tx.Bucket([]byte("widgets")) == nil {
+	err = db.View(func(snapshot SnapshotI) error {
+		if snapshot.Bucket([]byte("widgets")) == nil {
 			t.Fatal("expected bucket")
 		}
 
@@ -6058,8 +6064,8 @@ func TestTx_CreateBucketIfNotExists(t *testing.T) {
 	}
 
 	// Read the bucket through a separate transaction.
-	err = db.View(func(tx ITx) error {
-		if tx.Bucket([]byte("widgets")) == nil {
+	err = db.View(func(snapshot SnapshotI) error {
+		if snapshot.Bucket([]byte("widgets")) == nil {
 			t.Fatal("expected bucket")
 		}
 
@@ -6229,13 +6235,14 @@ func TestTx_DeleteBucket_ErrTxClosed(t *testing.T) {
 	}
 }
 
+/*
 // Ensure that deleting a bucket with a read-only transaction returns an error.
 func TestTx_DeleteBucket_ReadOnly(t *testing.T) {
 	db := MustOpenDB()
 	defer db.MustClose()
 	defer os.Remove(db.Path())
 
-	err := db.View(func(tx ITx) error {
+	err := db.View(func(snapshot SnapshotI) error {
 		err := tx.DeleteBucket([]byte("foo"))
 		if err != ErrTxNotWritable {
 			t.Fatalf("unexpected error: %s", err)
@@ -6247,6 +6254,7 @@ func TestTx_DeleteBucket_ReadOnly(t *testing.T) {
 		t.Fatal(err)
 	}
 }
+*/
 
 // Ensure that nothing happens when deleting a bucket that doesn't exist.
 func TestTx_DeleteBucket_NotFound(t *testing.T) {
@@ -6429,8 +6437,8 @@ func TestTx_WriteTo_Error_Meta(t *testing.T) {
 	}
 
 	const expectedMsg = "meta 0 copy: error injected for tests"
-	err = db.View(func(tx ITx) error {
-		_, err := tx.WriteTo(&failWriter{})
+	err = db.View(func(snapshot SnapshotI) error {
+		_, err := snapshot.WriteTo(&failWriter{})
 		return err
 	})
 	if err == nil || err.Error() != expectedMsg {
@@ -6466,8 +6474,8 @@ func TestTx_WriteTo_Error_Normal(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	err = db.View(func(tx ITx) error {
-		_, err := tx.WriteTo(&failWriter{3 * db.pageSize})
+	err = db.View(func(snapshot SnapshotI) error {
+		_, err := snapshot.WriteTo(&failWriter{3 * db.pageSize})
 		return err
 	})
 	if err == nil || err.Error() != "error injected for tests" {
@@ -6522,7 +6530,7 @@ func ExampleTx_Rollback() {
 	}
 
 	// Ensure that our original value is still set.
-	err = db.View(func(tx ITx) error {
+	err = db.View(func(snapshot SnapshotI) error {
 		value := tx.Bucket([]byte("widgets")).Get([]byte("foo"))
 		fmt.Printf("The value for 'foo' is still: %s\n", value)
 		return nil
@@ -6750,7 +6758,7 @@ func MainTest() {
 		{ "TestTx_Rollback_ErrTxClosed", TestTx_Rollback_ErrTxClosed },
 		{ "TestTx_Commit_ErrTxNotWritable", TestTx_Commit_ErrTxNotWritable },
 		{ "TestTx_Cursor", TestTx_Cursor },
-		{ "TestTx_CreateBucket_ErrTxNotWritable", TestTx_CreateBucket_ErrTxNotWritable },
+		// { "TestTx_CreateBucket_ErrTxNotWritable", TestTx_CreateBucket_ErrTxNotWritable },
 		{ "TestTx_CreateBucket_ErrTxClosed", TestTx_CreateBucket_ErrTxClosed },
 		{ "TestTx_Bucket", TestTx_Bucket },
 		{ "TestTx_Get_NotFound", TestTx_Get_NotFound },
@@ -6761,7 +6769,7 @@ func MainTest() {
 		{ "TestTx_CreateBucket_ErrBucketNameRequired", TestTx_CreateBucket_ErrBucketNameRequired },
 		{ "TestTx_DeleteBucket", TestTx_DeleteBucket },
 		{ "TestTx_DeleteBucket_ErrTxClosed", TestTx_DeleteBucket_ErrTxClosed },
-		{ "TestTx_DeleteBucket_ReadOnly", TestTx_DeleteBucket_ReadOnly },
+		// { "TestTx_DeleteBucket_ReadOnly", TestTx_DeleteBucket_ReadOnly },
 		{ "TestTx_DeleteBucket_NotFound", TestTx_DeleteBucket_NotFound },
 		{ "TestTx_ForEach_NoError", TestTx_ForEach_NoError },
 		{ "TestTx_ForEach_WithError", TestTx_ForEach_WithError },