1 // Copyright 2022 The ChromiumOS Authors 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 use std::cmp::min; 6 use std::fs::File; 7 use std::io; 8 use std::os::windows::fs::FileExt; 9 10 use crate::PunchHole; 11 12 // TODO(b/195151495): Fix so that this will extend a file size if needed. file_write_zeroes_at(file: &File, offset: u64, length: usize) -> io::Result<usize>13pub(crate) fn file_write_zeroes_at(file: &File, offset: u64, length: usize) -> io::Result<usize> { 14 // Try to punch a hole first. 15 if let Ok(()) = file.punch_hole(offset, length as u64) { 16 return Ok(length); 17 } 18 19 // fall back to write() 20 // punch_hole() failed; fall back to writing a buffer of zeroes 21 // until we have written up to length. 22 let buf_size = min(length, 0x10000); 23 let buf = vec![0u8; buf_size]; 24 let mut nwritten: usize = 0; 25 while nwritten < length { 26 let remaining = length - nwritten; 27 let write_size = min(remaining, buf_size); 28 nwritten += file.seek_write(&buf[0..write_size], offset + nwritten as u64)?; 29 } 30 Ok(length) 31 } 32