[pbs-devel] [RFC proxmox-backup 32/36] pxar: caching: add look-ahead cache types

[Christian Ebner <c.ebner@proxmox.com>]

The look-ahead cache is used to cache entries during pxar archive
creation before encoding, in order to decide if regular file payloads
might be re-used rather than re-encoded.

These types allow to store the needed data and keep track of
directory boundaries while traversing the filesystem tree.

Signed-off-by: Christian Ebner <c.ebner@proxmox.com>
---
 pbs-client/src/pxar/lookahead_cache.rs | 38 ++++++++++++++++++++++++++
 pbs-client/src/pxar/mod.rs             |  1 +
 2 files changed, 39 insertions(+)
 create mode 100644 pbs-client/src/pxar/lookahead_cache.rs

diff --git a/pbs-client/src/pxar/lookahead_cache.rs b/pbs-client/src/pxar/lookahead_cache.rs
new file mode 100644
index 00000000..68f3fd1f
--- /dev/null
+++ b/pbs-client/src/pxar/lookahead_cache.rs
@@ -0,0 +1,38 @@
+use nix::sys::stat::FileStat;
+use pxar::encoder::PayloadOffset;
+use std::ffi::CString;
+use std::os::unix::io::OwnedFd;
+
+use pxar::Metadata;
+
+pub(crate) struct CacheEntryData {
+    pub(crate) fd: OwnedFd,
+    pub(crate) c_file_name: CString,
+    pub(crate) stat: FileStat,
+    pub(crate) metadata: Metadata,
+    pub(crate) payload_offset: PayloadOffset,
+}
+
+impl CacheEntryData {
+    pub(crate) fn new(
+        fd: OwnedFd,
+        c_file_name: CString,
+        stat: FileStat,
+        metadata: Metadata,
+        payload_offset: PayloadOffset,
+    ) -> Self {
+        Self {
+            fd,
+            c_file_name,
+            stat,
+            metadata,
+            payload_offset,
+        }
+    }
+}
+
+pub(crate) enum CacheEntry {
+    RegEntry(CacheEntryData),
+    DirEntry(CacheEntryData),
+    DirEnd,
+}
diff --git a/pbs-client/src/pxar/mod.rs b/pbs-client/src/pxar/mod.rs
index 24315f5f..3729ab10 100644
--- a/pbs-client/src/pxar/mod.rs
+++ b/pbs-client/src/pxar/mod.rs
@@ -50,6 +50,7 @@
 pub(crate) mod create;
 pub(crate) mod dir_stack;
 pub(crate) mod extract;
+pub(crate) mod lookahead_cache;
 pub(crate) mod metadata;
 pub(crate) mod tools;
 
-- 
2.39.2