/*
 * Copyright 2020 Dgraph Labs, Inc. and Contributors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package z

import (
	"fmt"
)

// Truncate would truncate the mmapped file to the given size. On Linux, we truncate
// the underlying file and then call mremap, but on other systems, we unmap first,
// then truncate, then re-map.
func (m *MmapFile) Truncate(maxSz int64) error {
	if err := m.Sync(); err != nil {
		return fmt.Errorf("while sync file: %s, error: %v\n", m.Fd.Name(), err)
	}
	if err := m.Fd.Truncate(maxSz); err != nil {
		return fmt.Errorf("while truncate file: %s, error: %v\n", m.Fd.Name(), err)
	}

	var err error
	m.Data, err = mremap(m.Data, int(maxSz)) // Mmap up to max size.
	return err
}