datastore: add snapshot iterator and provide example

will be more used in the future, when the upend-datastore master plan
comes in effect.

also a preparatory work for namespaces

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>

pbs-datastore/examples/ls-snapshots.rs

@@ -0,0 +1,34 @@
+use std::path::PathBuf;
+
+use anyhow::{bail, Error};
+
+use pbs_datastore::{ListGroups, ListSnapshots};
+
+fn run() -> Result<(), Error> {
+    let base: PathBuf = match std::env::args().skip(1).next() {
+        Some(path) => path.into(),
+        None => bail!("no path passed"),
+    };
+
+    for group in ListGroups::new(base.to_owned())? {
+        let group = group?;
+        println!("found group {}", group);
+
+        let group_path = base.as_path().join(group.to_string());
+        for snapshot in ListSnapshots::new(group, group_path)? {
+            println!("\t{}", snapshot?);
+        }
+    }
+
+    Ok(())
+}
+
+fn main() {
+    std::process::exit(match run() {
+        Ok(_) => 0,
+        Err(err) => {
+            eprintln!("error: {}", err);
+            1
+        }
+    });
+}

pbs-datastore/src/datastore.rs

@@ -19,7 +19,7 @@ use proxmox_sys::{task_log, task_warn};
 
 use pbs_api_types::{
     Authid, ChunkOrder, DataStoreConfig, DatastoreTuning, GarbageCollectionStatus, HumanByte,
-    Operation, BACKUP_ID_REGEX, BACKUP_TYPE_REGEX, UPID,
+    Operation, BACKUP_DATE_REGEX, BACKUP_ID_REGEX, BACKUP_TYPE_REGEX, UPID,
 };
 use pbs_config::{open_backup_lockfile, BackupLockGuard, ConfigVersionCache};
 
@@ -1065,6 +1065,51 @@ impl DataStore {
     }
 }
 
+/// A iterator for all BackupDir's (Snapshots) in a BackupGroup
+pub struct ListSnapshots {
+    group: BackupGroup,
+    fd: proxmox_sys::fs::ReadDir,
+}
+
+impl ListSnapshots {
+    pub fn new(group: BackupGroup, group_path: PathBuf) -> Result<Self, Error> {
+        Ok(ListSnapshots {
+            fd: proxmox_sys::fs::read_subdir(libc::AT_FDCWD, &group_path)?,
+            group,
+        })
+    }
+}
+
+impl Iterator for ListSnapshots {
+    type Item = Result<BackupDir, Error>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        loop {
+            let item = self.fd.next()?;
+            match item {
+                Ok(ref entry) => {
+                    if let Ok(name) = entry.file_name().to_str() {
+                        match entry.file_type() {
+                            Some(nix::dir::Type::Directory) => {} // OK
+                            _ => continue,
+                        }
+                        if BACKUP_DATE_REGEX.is_match(name) {
+                            let backup_time = match proxmox_time::parse_rfc3339(&name) {
+                                Ok(time) => time,
+                                Err(err) => return Some(Err(err)),
+                            };
+
+                            return Some(BackupDir::with_group(self.group.clone(), backup_time));
+                        }
+                    }
+                    continue; // file did not match regex or isn't valid utf-8
+                }
+                Err(err) => return Some(Err(err)),
+            }
+        }
+    }
+}
+
 /// A iterator for a (single) level of Backup Groups
 pub struct ListGroups {
     type_fd: proxmox_sys::fs::ReadDir,

pbs-datastore/src/lib.rs

@@ -204,7 +204,7 @@ pub use manifest::BackupManifest;
 pub use store_progress::StoreProgress;
 
 mod datastore;
-pub use datastore::{check_backup_owner, DataStore, ListGroups};
+pub use datastore::{check_backup_owner, DataStore, ListGroups, ListSnapshots};
 
 mod snapshot_reader;
 pub use snapshot_reader::SnapshotReader;