1// Copyright 2021 The go-ethereum Authors
2// This file is part of the go-ethereum library.
3//
4// The go-ethereum library is free software: you can redistribute it and/or modify
5// it under the terms of the GNU Lesser General Public License as published by
6// the Free Software Foundation, either version 3 of the License, or
7// (at your option) any later version.
8//
9// The go-ethereum library is distributed in the hope that it will be useful,
10// but WITHOUT ANY WARRANTY; without even the implied warranty of
11// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12// GNU Lesser General Public License for more details.
13//
14// You should have received a copy of the GNU Lesser General Public License
15// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
16
17//go:build !linux
18// +build !linux
19
20package ethash
21
22import (
23	"os"
24)
25
26// ensureSize expands the file to the given size. This is to prevent runtime
27// errors later on, if the underlying file expands beyond the disk capacity,
28// even though it ostensibly is already expanded, but due to being sparse
29// does not actually occupy the full declared size on disk.
30func ensureSize(f *os.File, size int64) error {
31	// On systems which do not support fallocate, we merely truncate it.
32	// More robust alternatives  would be to
33	// - Use posix_fallocate, or
34	// - explicitly fill the file with zeroes.
35	return f.Truncate(size)
36}
37