src/bin/dynamic-files.rs: test case for file shrink during backup

src/bin/dynamic-files.rs

@@ -0,0 +1,62 @@
+use failure::*;
+
+use std::thread;
+use std::path::PathBuf;
+use std::io::Write;
+
+// tar handle files that shrink during backup, by simply padding with zeros.
+//
+// this binary run multiple thread which writes some large files, then truncates
+// them in a loop.
+
+// # tar cf test.tar ./dyntest1/
+// tar: dyntest1/testfile0.dat: File shrank by 2768972800 bytes; padding with zeros
+// tar: dyntest1/testfile17.dat: File shrank by 2899853312 bytes; padding with zeros
+// tar: dyntest1/testfile2.dat: File shrank by 3093422080 bytes; padding with zeros
+// tar: dyntest1/testfile7.dat: File shrank by 2833252864 bytes; padding with zeros
+
+// # pxar create test.pxar ./dyntest1/
+// Error: detected shrinked file "./dyntest1/testfile0.dat" (22020096 < 12679380992)
+
+fn create_large_file(path: PathBuf) {
+
+    println!("TEST {:?}", path);
+
+    let mut file = std::fs::OpenOptions::new()
+        .write(true)
+        .create_new(true)
+        .open(&path).unwrap();
+
+    let buffer = vec![0u8; 64*1024];
+
+    loop {
+        for _ in 0..64 {
+            file.write_all(&buffer).unwrap();
+        }
+        file.sync_all().unwrap();
+        //println!("TRUNCATE {:?}", path);
+        file.set_len(0).unwrap();
+    }
+}
+
+fn main() -> Result<(), Error> {
+
+    let base = PathBuf::from("dyntest1");
+    let _ = std::fs::create_dir(&base);
+
+    let mut handles = vec![];
+    for i in 0..20 {
+        let base = base.clone();
+        handles.push(thread::spawn(move || {
+            create_large_file(base.join(format!("testfile{}.dat", i)));
+        }));
+    }
+
+    for h in handles {
+        if let Err(_) = h.join() {
+            bail!("join failed");
+        }
+    }
+
+    Ok(())
+}