func ExampleTx_CopyFile() {
	// Open the database.
	db, _ := bolt.Open(tempfile(), 0666, nil)
	defer os.Remove(db.Path())
	defer db.Close()

	// Create a bucket and a key.
	db.Update(func(tx *bolt.Tx) error {
		tx.CreateBucket([]byte("widgets"))
		tx.Bucket([]byte("widgets")).Put([]byte("foo"), []byte("bar"))
		return nil
	})

	// Copy the database to another file.
	toFile := tempfile()
	db.View(func(tx *bolt.Tx) error { return tx.CopyFile(toFile, 0666) })
	defer os.Remove(toFile)

	// Open the cloned database.
	db2, _ := bolt.Open(toFile, 0666, nil)
	defer db2.Close()

	// Ensure that the key exists in the copy.
	db2.View(func(tx *bolt.Tx) error {
		value := tx.Bucket([]byte("widgets")).Get([]byte("foo"))
		fmt.Printf("The value for 'foo' in the clone is: %s\n", value)
		return nil
	})

	// Output:
	// The value for 'foo' in the clone is: bar
}

// Ensure that opening an already open database file will wait until its closed.
func TestOpen_Wait(t *testing.T) {
	if runtime.GOOS == "windows" {
		t.Skip("timeout not supported on windows")
	}
	if runtime.GOOS == "solaris" {
		t.Skip("solaris fcntl locks don't support intra-process locking")
	}

	path := tempfile()
	defer os.Remove(path)

	// Open a data file.
	db0, err := bolt.Open(path, 0666, nil)
	assert(t, db0 != nil, "")
	ok(t, err)

	// Close it in just a bit.
	time.AfterFunc(100*time.Millisecond, func() { db0.Close() })

	// Attempt to open the database again.
	start := time.Now()
	db1, err := bolt.Open(path, 0666, &bolt.Options{Timeout: 200 * time.Millisecond})
	assert(t, db1 != nil, "")
	ok(t, err)
	assert(t, time.Since(start) > 100*time.Millisecond, "")
}

func (b *backend) Defrag() error {
	// TODO: make this non-blocking?
	// lock batchTx to ensure nobody is using previous tx, and then
	// close previous ongoing tx.
	b.batchTx.Lock()
	defer b.batchTx.Unlock()

	// lock database after lock tx to avoid deadlock.
	b.mu.Lock()
	defer b.mu.Unlock()

	b.batchTx.commit(true)
	b.batchTx.tx = nil

	tmpdb, err := bolt.Open(b.db.Path()+".tmp", 0600, boltOpenOptions)
	if err != nil {
		return err
	}

	err = defragdb(b.db, tmpdb, defragLimit)

	if err != nil {
		tmpdb.Close()
		os.RemoveAll(tmpdb.Path())
		return err
	}

	dbp := b.db.Path()
	tdbp := tmpdb.Path()

	err = b.db.Close()
	if err != nil {
		log.Fatalf("backend: cannot close database (%s)", err)
	}
	err = tmpdb.Close()
	if err != nil {
		log.Fatalf("backend: cannot close database (%s)", err)
	}
	err = os.Rename(tdbp, dbp)
	if err != nil {
		log.Fatalf("backend: cannot rename database (%s)", err)
	}

	b.db, err = bolt.Open(dbp, 0600, boltOpenOptions)
	if err != nil {
		log.Panicf("backend: cannot open database at %s (%v)", dbp, err)
	}
	b.batchTx.tx, err = b.db.Begin(true)
	if err != nil {
		log.Fatalf("backend: cannot begin tx (%s)", err)
	}

	return nil
}

// Ensure that a re-opened database is consistent.
func TestOpen_Check(t *testing.T) {
	path := tempfile()
	defer os.Remove(path)

	db, err := bolt.Open(path, 0666, nil)
	ok(t, err)
	ok(t, db.View(func(tx *bolt.Tx) error { return <-tx.Check() }))
	db.Close()

	db, err = bolt.Open(path, 0666, nil)
	ok(t, err)
	ok(t, db.View(func(tx *bolt.Tx) error { return <-tx.Check() }))
	db.Close()
}

// Ensure that a database that is too small returns an error.
func TestDB_Open_FileTooSmall(t *testing.T) {
	path := tempfile()
	defer os.Remove(path)

	db, err := bolt.Open(path, 0666, nil)
	ok(t, err)
	db.Close()

	// corrupt the database
	ok(t, os.Truncate(path, int64(os.Getpagesize())))

	db, err = bolt.Open(path, 0666, nil)
	equals(t, errors.New("file size too small"), err)
}

// Run executes the command.
func (cmd *InfoCommand) Run(args ...string) error {
	// Parse flags.
	fs := flag.NewFlagSet("", flag.ContinueOnError)
	help := fs.Bool("h", false, "")
	if err := fs.Parse(args); err != nil {
		return err
	} else if *help {
		fmt.Fprintln(cmd.Stderr, cmd.Usage())
		return ErrUsage
	}

	// Require database path.
	path := fs.Arg(0)
	if path == "" {
		return ErrPathRequired
	} else if _, err := os.Stat(path); os.IsNotExist(err) {
		return ErrFileNotFound
	}

	// Open the database.
	db, err := bolt.Open(path, 0666, nil)
	if err != nil {
		return err
	}
	defer db.Close()

	// Print basic database info.
	info := db.Info()
	fmt.Fprintf(cmd.Stdout, "Page Size: %d\n", info.PageSize)

	return nil
}

func ExampleTx_Rollback() {
	// Open the database.
	db, _ := bolt.Open(tempfile(), 0666, nil)
	defer os.Remove(db.Path())
	defer db.Close()

	// Create a bucket.
	db.Update(func(tx *bolt.Tx) error {
		_, err := tx.CreateBucket([]byte("widgets"))
		return err
	})

	// Set a value for a key.
	db.Update(func(tx *bolt.Tx) error {
		return tx.Bucket([]byte("widgets")).Put([]byte("foo"), []byte("bar"))
	})

	// Update the key but rollback the transaction so it never saves.
	tx, _ := db.Begin(true)
	b := tx.Bucket([]byte("widgets"))
	b.Put([]byte("foo"), []byte("baz"))
	tx.Rollback()

	// Ensure that our original value is still set.
	db.View(func(tx *bolt.Tx) error {
		value := tx.Bucket([]byte("widgets")).Get([]byte("foo"))
		fmt.Printf("The value for 'foo' is still: %s\n", value)
		return nil
	})

	// Output:
	// The value for 'foo' is still: bar
}

func ExampleBucket_ForEach() {
	// Open the database.
	db, _ := bolt.Open(tempfile(), 0666, nil)
	defer os.Remove(db.Path())
	defer db.Close()

	// Insert data into a bucket.
	db.Update(func(tx *bolt.Tx) error {
		tx.CreateBucket([]byte("animals"))
		b := tx.Bucket([]byte("animals"))
		b.Put([]byte("dog"), []byte("fun"))
		b.Put([]byte("cat"), []byte("lame"))
		b.Put([]byte("liger"), []byte("awesome"))

		// Iterate over items in sorted key order.
		b.ForEach(func(k, v []byte) error {
			fmt.Printf("A %s is %s.\n", k, v)
			return nil
		})
		return nil
	})

	// Output:
	// A cat is lame.
	// A dog is fun.
	// A liger is awesome.
}

func ExampleDB_View() {
	// Open the database.
	db, _ := bolt.Open(tempfile(), 0666, nil)
	defer os.Remove(db.Path())
	defer db.Close()

	// Insert data into a bucket.
	db.Update(func(tx *bolt.Tx) error {
		tx.CreateBucket([]byte("people"))
		b := tx.Bucket([]byte("people"))
		b.Put([]byte("john"), []byte("doe"))
		b.Put([]byte("susy"), []byte("que"))
		return nil
	})

	// Access data from within a read-only transactional block.
	db.View(func(tx *bolt.Tx) error {
		v := tx.Bucket([]byte("people")).Get([]byte("john"))
		fmt.Printf("John's last name is %s.\n", v)
		return nil
	})

	// Output:
	// John's last name is doe.
}

func ExampleDB_Begin_ReadOnly() {
	// Open the database.
	db, _ := bolt.Open(tempfile(), 0666, nil)
	defer os.Remove(db.Path())
	defer db.Close()

	// Create a bucket.
	db.Update(func(tx *bolt.Tx) error {
		_, err := tx.CreateBucket([]byte("widgets"))
		return err
	})

	// Create several keys in a transaction.
	tx, _ := db.Begin(true)
	b := tx.Bucket([]byte("widgets"))
	b.Put([]byte("john"), []byte("blue"))
	b.Put([]byte("abby"), []byte("red"))
	b.Put([]byte("zephyr"), []byte("purple"))
	tx.Commit()

	// Iterate over the values in sorted key order.
	tx, _ = db.Begin(false)
	c := tx.Bucket([]byte("widgets")).Cursor()
	for k, v := c.First(); k != nil; k, v = c.Next() {
		fmt.Printf("%s likes %s\n", k, v)
	}
	tx.Rollback()

	// Output:
	// abby likes red
	// john likes blue
	// zephyr likes purple
}

// NewTestDB returns a new instance of TestDB.
func NewTestDB() *TestDB {
	db, err := bolt.Open(tempfile(), 0666, nil)
	if err != nil {
		panic("cannot open db: " + err.Error())
	}
	return &TestDB{db}
}

func ExampleBucket_Put() {
	// Open the database.
	db, _ := bolt.Open(tempfile(), 0666, nil)
	defer os.Remove(db.Path())
	defer db.Close()

	// Start a write transaction.
	db.Update(func(tx *bolt.Tx) error {
		// Create a bucket.
		tx.CreateBucket([]byte("widgets"))

		// Set the value "bar" for the key "foo".
		tx.Bucket([]byte("widgets")).Put([]byte("foo"), []byte("bar"))
		return nil
	})

	// Read value back in a different read-only transaction.
	db.View(func(tx *bolt.Tx) error {
		value := tx.Bucket([]byte("widgets")).Get([]byte("foo"))
		fmt.Printf("The value of 'foo' is: %s\n", value)
		return nil
	})

	// Output:
	// The value of 'foo' is: bar
}

func ExampleDB_Update() {
	// Open the database.
	db, _ := bolt.Open(tempfile(), 0666, nil)
	defer os.Remove(db.Path())
	defer db.Close()

	// Execute several commands within a write transaction.
	err := db.Update(func(tx *bolt.Tx) error {
		b, err := tx.CreateBucket([]byte("widgets"))
		if err != nil {
			return err
		}
		if err := b.Put([]byte("foo"), []byte("bar")); err != nil {
			return err
		}
		return nil
	})

	// If our transactional block didn't return an error then our data is saved.
	if err == nil {
		db.View(func(tx *bolt.Tx) error {
			value := tx.Bucket([]byte("widgets")).Get([]byte("foo"))
			fmt.Printf("The value of 'foo' is: %s\n", value)
			return nil
		})
	}

	// Output:
	// The value of 'foo' is: bar
}

// Ensure that the database returns an error if the file handle cannot be open.
func TestDB_Open_FileError(t *testing.T) {
	path := tempfile()
	defer os.Remove(path)

	_, err := bolt.Open(path+"/youre-not-my-real-parent", 0666, nil)
	assert(t, err.(*os.PathError) != nil, "")
	equals(t, path+"/youre-not-my-real-parent", err.(*os.PathError).Path)
	equals(t, "open", err.(*os.PathError).Op)
}

// Ensure that a database can be opened without error.
func TestOpen(t *testing.T) {
	path := tempfile()
	defer os.Remove(path)
	db, err := bolt.Open(path, 0666, nil)
	assert(t, db != nil, "")
	ok(t, err)
	equals(t, db.Path(), path)
	ok(t, db.Close())
}

func ExampleDB_Batch() {
	// Open the database.
	db, _ := bolt.Open(tempfile(), 0666, nil)
	defer os.Remove(db.Path())
	defer db.Close()

	// Start our web server
	count := counter{db}
	srv := httptest.NewServer(count)
	defer srv.Close()

	// Decrease the batch size to make things more interesting.
	db.MaxBatchSize = 3

	// Get every path multiple times concurrently.
	const clients = 10
	paths := []string{
		"/foo",
		"/bar",
		"/baz",
		"/quux",
		"/thud",
		"/xyzzy",
	}
	errors := make(chan error, clients)
	for i := 0; i < clients; i++ {
		go func(id int) {
			errors <- client(id, srv.URL, paths)
		}(i)
	}
	// Check all responses to make sure there's no error.
	for i := 0; i < clients; i++ {
		if err := <-errors; err != nil {
			fmt.Printf("client error: %v", err)
			return
		}
	}

	// Check the final result
	db.View(func(tx *bolt.Tx) error {
		b := tx.Bucket([]byte("hits"))
		c := b.Cursor()
		for k, v := c.First(); k != nil; k, v = c.Next() {
			fmt.Printf("hits to %s: %d\n", k, decode(v))
		}
		return nil
	})

	// Output:
	// hits to /bar: 10
	// hits to /baz: 10
	// hits to /foo: 10
	// hits to /quux: 10
	// hits to /thud: 10
	// hits to /xyzzy: 10
}

// MustOpen creates a Bolt database in a temporary location.
func MustOpen(mode os.FileMode, options *bolt.Options) *DB {
	// Create temporary path.
	f, _ := ioutil.TempFile("", "bolt-")
	f.Close()
	os.Remove(f.Name())

	db, err := bolt.Open(f.Name(), mode, options)
	if err != nil {
		panic(err.Error())
	}
	return &DB{DB: db, Path: f.Name()}
}

// Ensure that opening an already open database file will timeout.
func TestOpen_Timeout(t *testing.T) {
	if runtime.GOOS == "solaris" {
		t.Skip("solaris fcntl locks don't support intra-process locking")
	}

	path := tempfile()
	defer os.Remove(path)

	// Open a data file.
	db0, err := bolt.Open(path, 0666, nil)
	assert(t, db0 != nil, "")
	ok(t, err)

	// Attempt to open the database again.
	start := time.Now()
	db1, err := bolt.Open(path, 0666, &bolt.Options{Timeout: 100 * time.Millisecond})
	assert(t, db1 == nil, "")
	equals(t, bolt.ErrTimeout, err)
	assert(t, time.Since(start) > 100*time.Millisecond, "")

	db0.Close()
}

// Ensure that opening a database beyond the max step size does not increase its size.
// https://github.com/boltdb/bolt/issues/303
func TestOpen_Size_Large(t *testing.T) {
	if testing.Short() {
		t.Skip("short mode")
	}

	// Open a data file.
	db := NewTestDB()
	path := db.Path()
	defer db.Close()

	// Insert until we get above the minimum 4MB size.
	var index uint64
	for i := 0; i < 10000; i++ {
		ok(t, db.Update(func(tx *bolt.Tx) error {
			b, _ := tx.CreateBucketIfNotExists([]byte("data"))
			for j := 0; j < 1000; j++ {
				ok(t, b.Put(u64tob(index), make([]byte, 50)))
				index++
			}
			return nil
		}))
	}

	// Close database and grab the size.
	db.DB.Close()
	sz := fileSize(path)
	if sz == 0 {
		t.Fatalf("unexpected new file size: %d", sz)
	} else if sz < (1 << 30) {
		t.Fatalf("expected larger initial size: %d", sz)
	}

	// Reopen database, update, and check size again.
	db0, err := bolt.Open(path, 0666, nil)
	ok(t, err)
	ok(t, db0.Update(func(tx *bolt.Tx) error { return tx.Bucket([]byte("data")).Put([]byte{0}, []byte{0}) }))
	ok(t, db0.Close())
	newSz := fileSize(path)
	if newSz == 0 {
		t.Fatalf("unexpected new file size: %d", newSz)
	}

	// Compare the original size with the new size.
	if sz != newSz {
		t.Fatalf("unexpected file growth: %d => %d", sz, newSz)
	}
}

func newBackend(path string, d time.Duration, limit int) *backend {
	db, err := bolt.Open(path, 0600, boltOpenOptions)
	if err != nil {
		log.Panicf("backend: cannot open database at %s (%v)", path, err)
	}

	b := &backend{
		db: db,

		batchInterval: d,
		batchLimit:    limit,

		stopc: make(chan struct{}),
		donec: make(chan struct{}),
	}
	b.batchTx = newBatchTx(b)
	go b.run()
	return b
}