backup: add ChunkIterator

Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>

src/backup/chunk_store.rs

@@ -7,9 +7,10 @@ use openssl::sha;
 use std::sync::Mutex;
 
 use std::fs::File;
-use std::os::unix::io::AsRawFd;
+use std::os::unix::io::{AsRawFd, RawFd};
 
 use crate::tools;
+use crate::tools::borrow::Tied;
 
 pub struct GarbageCollectionStatus {
     pub used_bytes: usize,
@@ -56,6 +57,83 @@ fn digest_to_prefix(digest: &[u8]) -> PathBuf {
     path.into()
 }
 
+// This is one thing which would actually get nicer with futures & tokio-fs...
+pub struct ChunkIterator {
+    base_dir: nix::dir::Dir,
+    index: usize,
+    subdir: Option<
+        Tied<nix::dir::Dir, Iterator<Item = nix::Result<nix::dir::Entry>>>
+        >,
+    subdir_fd: RawFd,
+}
+
+impl ChunkIterator {
+    fn new(base_dir: nix::dir::Dir) -> Self {
+        ChunkIterator {
+            base_dir,
+            index: 0,
+            subdir: None,
+            subdir_fd: 0,
+        }
+    }
+
+    fn next_subdir(&mut self) -> Result<bool, Error> {
+        if self.index == 0x10000 {
+            return Ok(false);
+        }
+
+        let l1name = PathBuf::from(format!("{:04x}", self.index));
+        self.index += 1;
+
+        use nix::dir::{Dir, Entry};
+        use nix::fcntl::OFlag;
+        use nix::sys::stat::Mode;
+        match Dir::openat(self.base_dir.as_raw_fd(), &l1name, OFlag::O_RDONLY, Mode::empty()) {
+            Ok(dir) => {
+                self.subdir_fd = dir.as_raw_fd();
+                self.subdir = Some(Tied::new(dir, |dir| {
+                    Box::new(unsafe { (*dir).iter() })
+                    as Box<Iterator<Item = nix::Result<Entry>>>
+                }));
+                return Ok(true);
+            }
+            Err(err) => {
+                self.index = 0x10000;
+                bail!("unable to open chunk dir {:?}: {}", l1name, err);
+            }
+        }
+    }
+}
+
+impl Iterator for ChunkIterator {
+    type Item = Result<(RawFd, nix::dir::Entry), Error>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        loop {
+            match self.subdir {
+                None => {
+                    match self.next_subdir() {
+                        Ok(true) => continue, // Enter the Some case
+                        Ok(false) => return None,
+                        Err(e) => return Some(Err(e)),
+                    }
+                }
+                Some(ref mut dir) => {
+                    let dir = dir.as_mut();
+                    match dir.next() {
+                        Some(Ok(entry)) => return Some(Ok((self.subdir_fd, entry))),
+                        Some(Err(e)) => return Some(Err(e.into())),
+                        None => {
+                            // Go to the next directory
+                            self.subdir = None;
+                            continue;
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
 
 impl ChunkStore {