| // Copyright 2018 The Chromium OS Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| use std::fs::File; |
| use std::io::{Error, Result}; |
| use std::os::unix::io::AsRawFd; |
| |
| use libc::{lseek64, ENXIO, SEEK_DATA, SEEK_HOLE}; |
| |
| /// A trait for seeking to the next hole or non-hole position in a file. |
| pub trait SeekHole { |
| /// Seek to the first hole in a file at a position greater than or equal to `offset`. |
| /// If no holes exist after `offset`, the seek position will be set to the end of the file. |
| /// If `offset` is at or after the end of the file, the seek position is unchanged, and None is returned. |
| /// Returns the current seek position after the seek or an error. |
| fn seek_hole(&mut self, offset: u64) -> Result<Option<u64>>; |
| |
| /// Seek to the first data in a file at a position greater than or equal to `offset`. |
| /// If no data exists after `offset`, the seek position is unchanged, and None is returned. |
| /// Returns the current offset after the seek or an error. |
| fn seek_data(&mut self, offset: u64) -> Result<Option<u64>>; |
| } |
| |
| /// Safe wrapper for `libc::lseek64()` |
| fn lseek(file: &mut File, offset: i64, whence: i32) -> Result<Option<u64>> { |
| // This is safe because we pass a known-good file descriptor. |
| let res = unsafe { lseek64(file.as_raw_fd(), offset, whence) }; |
| |
| if res < 0 { |
| // Convert ENXIO into None; pass any other error as-is. |
| let err = Error::last_os_error(); |
| if let Some(errno) = Error::raw_os_error(&err) { |
| if errno == ENXIO { |
| return Ok(None); |
| } |
| } |
| Err(err) |
| } else { |
| Ok(Some(res as u64)) |
| } |
| } |
| |
| impl SeekHole for File { |
| fn seek_hole(&mut self, offset: u64) -> Result<Option<u64>> { |
| lseek(self, offset as i64, SEEK_HOLE) |
| } |
| |
| fn seek_data(&mut self, offset: u64) -> Result<Option<u64>> { |
| lseek(self, offset as i64, SEEK_DATA) |
| } |
| } |
| |
| #[cfg(test)] |
| mod tests { |
| use super::*; |
| use crate::TempDir; |
| use std::fs::File; |
| use std::io::{Seek, SeekFrom, Write}; |
| use std::path::PathBuf; |
| |
| fn seek_cur(file: &mut File) -> u64 { |
| file.seek(SeekFrom::Current(0)).unwrap() |
| } |
| |
| #[test] |
| fn seek_data() { |
| let tempdir = TempDir::new("/tmp/seek_data_test").unwrap(); |
| let mut path = PathBuf::from(tempdir.as_path().unwrap()); |
| path.push("test_file"); |
| let mut file = File::create(&path).unwrap(); |
| |
| // Empty file |
| assert_eq!(file.seek_data(0).unwrap(), None); |
| assert_eq!(seek_cur(&mut file), 0); |
| |
| // File with non-zero length consisting entirely of a hole |
| file.set_len(0x10000).unwrap(); |
| assert_eq!(file.seek_data(0).unwrap(), None); |
| assert_eq!(seek_cur(&mut file), 0); |
| |
| // seek_data at or after the end of the file should return None |
| assert_eq!(file.seek_data(0x10000).unwrap(), None); |
| assert_eq!(seek_cur(&mut file), 0); |
| assert_eq!(file.seek_data(0x10001).unwrap(), None); |
| assert_eq!(seek_cur(&mut file), 0); |
| |
| // Write some data to [0x10000, 0x20000) |
| let b = [0x55u8; 0x10000]; |
| file.seek(SeekFrom::Start(0x10000)).unwrap(); |
| file.write_all(&b).unwrap(); |
| assert_eq!(file.seek_data(0).unwrap(), Some(0x10000)); |
| assert_eq!(seek_cur(&mut file), 0x10000); |
| |
| // seek_data within data should return the same offset |
| assert_eq!(file.seek_data(0x10000).unwrap(), Some(0x10000)); |
| assert_eq!(seek_cur(&mut file), 0x10000); |
| assert_eq!(file.seek_data(0x10001).unwrap(), Some(0x10001)); |
| assert_eq!(seek_cur(&mut file), 0x10001); |
| assert_eq!(file.seek_data(0x1FFFF).unwrap(), Some(0x1FFFF)); |
| assert_eq!(seek_cur(&mut file), 0x1FFFF); |
| |
| // Extend the file to add another hole after the data |
| file.set_len(0x30000).unwrap(); |
| assert_eq!(file.seek_data(0).unwrap(), Some(0x10000)); |
| assert_eq!(seek_cur(&mut file), 0x10000); |
| assert_eq!(file.seek_data(0x1FFFF).unwrap(), Some(0x1FFFF)); |
| assert_eq!(seek_cur(&mut file), 0x1FFFF); |
| assert_eq!(file.seek_data(0x20000).unwrap(), None); |
| assert_eq!(seek_cur(&mut file), 0x1FFFF); |
| } |
| |
| #[test] |
| fn seek_hole() { |
| let tempdir = TempDir::new("/tmp/seek_hole_test").unwrap(); |
| let mut path = PathBuf::from(tempdir.as_path().unwrap()); |
| path.push("test_file"); |
| let mut file = File::create(&path).unwrap(); |
| |
| // Empty file |
| assert_eq!(file.seek_hole(0).unwrap(), None); |
| assert_eq!(seek_cur(&mut file), 0); |
| |
| // File with non-zero length consisting entirely of a hole |
| file.set_len(0x10000).unwrap(); |
| assert_eq!(file.seek_hole(0).unwrap(), Some(0)); |
| assert_eq!(seek_cur(&mut file), 0); |
| assert_eq!(file.seek_hole(0xFFFF).unwrap(), Some(0xFFFF)); |
| assert_eq!(seek_cur(&mut file), 0xFFFF); |
| |
| // seek_hole at or after the end of the file should return None |
| file.seek(SeekFrom::Start(0)).unwrap(); |
| assert_eq!(file.seek_hole(0x10000).unwrap(), None); |
| assert_eq!(seek_cur(&mut file), 0); |
| assert_eq!(file.seek_hole(0x10001).unwrap(), None); |
| assert_eq!(seek_cur(&mut file), 0); |
| |
| // Write some data to [0x10000, 0x20000) |
| let b = [0x55u8; 0x10000]; |
| file.seek(SeekFrom::Start(0x10000)).unwrap(); |
| file.write_all(&b).unwrap(); |
| |
| // seek_hole within a hole should return the same offset |
| assert_eq!(file.seek_hole(0).unwrap(), Some(0)); |
| assert_eq!(seek_cur(&mut file), 0); |
| assert_eq!(file.seek_hole(0xFFFF).unwrap(), Some(0xFFFF)); |
| assert_eq!(seek_cur(&mut file), 0xFFFF); |
| |
| // seek_hole within data should return the next hole (EOF) |
| file.seek(SeekFrom::Start(0)).unwrap(); |
| assert_eq!(file.seek_hole(0x10000).unwrap(), Some(0x20000)); |
| assert_eq!(seek_cur(&mut file), 0x20000); |
| file.seek(SeekFrom::Start(0)).unwrap(); |
| assert_eq!(file.seek_hole(0x10001).unwrap(), Some(0x20000)); |
| assert_eq!(seek_cur(&mut file), 0x20000); |
| file.seek(SeekFrom::Start(0)).unwrap(); |
| assert_eq!(file.seek_hole(0x1FFFF).unwrap(), Some(0x20000)); |
| assert_eq!(seek_cur(&mut file), 0x20000); |
| |
| // seek_hole at EOF after data should return None |
| file.seek(SeekFrom::Start(0)).unwrap(); |
| assert_eq!(file.seek_hole(0x20000).unwrap(), None); |
| assert_eq!(seek_cur(&mut file), 0); |
| |
| // Extend the file to add another hole after the data |
| file.set_len(0x30000).unwrap(); |
| assert_eq!(file.seek_hole(0).unwrap(), Some(0)); |
| assert_eq!(seek_cur(&mut file), 0); |
| assert_eq!(file.seek_hole(0xFFFF).unwrap(), Some(0xFFFF)); |
| assert_eq!(seek_cur(&mut file), 0xFFFF); |
| file.seek(SeekFrom::Start(0)).unwrap(); |
| assert_eq!(file.seek_hole(0x10000).unwrap(), Some(0x20000)); |
| assert_eq!(seek_cur(&mut file), 0x20000); |
| file.seek(SeekFrom::Start(0)).unwrap(); |
| assert_eq!(file.seek_hole(0x1FFFF).unwrap(), Some(0x20000)); |
| assert_eq!(seek_cur(&mut file), 0x20000); |
| file.seek(SeekFrom::Start(0)).unwrap(); |
| assert_eq!(file.seek_hole(0x20000).unwrap(), Some(0x20000)); |
| assert_eq!(seek_cur(&mut file), 0x20000); |
| file.seek(SeekFrom::Start(0)).unwrap(); |
| assert_eq!(file.seek_hole(0x20001).unwrap(), Some(0x20001)); |
| assert_eq!(seek_cur(&mut file), 0x20001); |
| |
| // seek_hole at EOF after a hole should return None |
| file.seek(SeekFrom::Start(0)).unwrap(); |
| assert_eq!(file.seek_hole(0x30000).unwrap(), None); |
| assert_eq!(seek_cur(&mut file), 0); |
| |
| // Write some data to [0x20000, 0x30000) |
| file.seek(SeekFrom::Start(0x20000)).unwrap(); |
| file.write_all(&b).unwrap(); |
| |
| // seek_hole within [0x20000, 0x30000) should now find the hole at EOF |
| assert_eq!(file.seek_hole(0x20000).unwrap(), Some(0x30000)); |
| assert_eq!(seek_cur(&mut file), 0x30000); |
| file.seek(SeekFrom::Start(0)).unwrap(); |
| assert_eq!(file.seek_hole(0x20001).unwrap(), Some(0x30000)); |
| assert_eq!(seek_cur(&mut file), 0x30000); |
| file.seek(SeekFrom::Start(0)).unwrap(); |
| assert_eq!(file.seek_hole(0x30000).unwrap(), None); |
| assert_eq!(seek_cur(&mut file), 0); |
| } |
| } |