examples/dynamic-files.rs

   1 use anyhow::{bail, Error};
   2
   3 use std::thread;
   4 use std::path::PathBuf;
   5 use std::io::Write;
   6
   7 // tar handle files that shrink during backup, by simply padding with zeros.
   8 //
   9 // this binary run multiple thread which writes some large files, then truncates
  10 // them in a loop.
  11
  12 // # tar cf test.tar ./dyntest1/
  13 // tar: dyntest1/testfile0.dat: File shrank by 2768972800 bytes; padding with zeros
  14 // tar: dyntest1/testfile17.dat: File shrank by 2899853312 bytes; padding with zeros
  15 // tar: dyntest1/testfile2.dat: File shrank by 3093422080 bytes; padding with zeros
  16 // tar: dyntest1/testfile7.dat: File shrank by 2833252864 bytes; padding with zeros
  17
  18 // # pxar create test.pxar ./dyntest1/
  19 // Error: detected shrunk file "./dyntest1/testfile0.dat" (22020096 < 12679380992)
  20
  21 fn create_large_file(path: PathBuf) {
  22
  23     println!("TEST {:?}", path);
  24
  25     let mut file = std::fs::OpenOptions::new()
  26         .write(true)
  27         .create_new(true)
  28         .open(&path).unwrap();
  29
  30     let buffer = vec![0u8; 64*1024];
  31
  32     loop {
  33         for _ in 0..64 {
  34             file.write_all(&buffer).unwrap();
  35         }
  36         file.sync_all().unwrap();
  37         //println!("TRUNCATE {:?}", path);
  38         file.set_len(0).unwrap();
  39     }
  40 }
  41
  42 fn main() -> Result<(), Error> {
  43
  44     let base = PathBuf::from("dyntest1");
  45     let _ = std::fs::create_dir(&base);
  46
  47     let mut handles = vec![];
  48     for i in 0..20 {
  49         let base = base.clone();
  50         handles.push(thread::spawn(move || {
  51             create_large_file(base.join(format!("testfile{}.dat", i)));
  52         }));
  53     }
  54
  55     for h in handles {
  56         if h.join().is_err() {
  57             bail!("join failed");
  58         }
  59     }
  60
  61     Ok(())
  62 }