[pbs-devel] [PATCH v3 proxmox-backup 37/58] client: pxar: helper for lookup of reusable dynamic entries

[Christian Ebner]

The helper method allows to lookup the entries of a dynamic index
which fully cover a given offset range. Further, the helper returns
the start padding from the start offset of the dynamic index entry
to the start offset of the given range and the end padding.

This will be used to lookup size and digest for chunks covering the
payload range of a regular file in order to re-use found chunks by
indexing them in the archives index file instead of re-encoding the
payload.

Signed-off-by: Christian Ebner <c.ebner at proxmox.com>
---
changes since version 2:
- moved this from the dynamic index to the pxar create as suggested
- refactored and optimized search, going for linear search to find the
  end entry
- reworded commit message

 pbs-client/src/pxar/create.rs | 63 +++++++++++++++++++++++++++++++++++
 1 file changed, 63 insertions(+)

diff --git a/pbs-client/src/pxar/create.rs b/pbs-client/src/pxar/create.rs
index 2bb5a6253..e2d3954ca 100644
--- a/pbs-client/src/pxar/create.rs
+++ b/pbs-client/src/pxar/create.rs
@@ -2,6 +2,7 @@ use std::collections::{HashMap, HashSet};
 use std::ffi::{CStr, CString, OsStr};
 use std::fmt;
 use std::io::{self, Read};
+use std::ops::Range;
 use std::os::unix::ffi::OsStrExt;
 use std::os::unix::io::{AsRawFd, FromRawFd, IntoRawFd, OwnedFd, RawFd};
 use std::path::{Path, PathBuf};
@@ -16,6 +17,7 @@ use nix::fcntl::OFlag;
 use nix::sys::stat::{FileStat, Mode};
 
 use pathpatterns::{MatchEntry, MatchFlag, MatchList, MatchType, PatternFlag};
+use pbs_datastore::index::IndexFile;
 use proxmox_sys::error::SysError;
 use pxar::encoder::{LinkOffset, SeqWrite};
 use pxar::Metadata;
@@ -25,6 +27,7 @@ use proxmox_lang::c_str;
 use proxmox_sys::fs::{self, acl, xattr};
 
 use pbs_datastore::catalog::BackupCatalogWriter;
+use pbs_datastore::dynamic_index::DynamicIndexReader;
 
 use crate::pxar::metadata::errno_is_unsupported;
 use crate::pxar::tools::assert_single_path_component;
@@ -791,6 +794,66 @@ impl Archiver {
     }
 }
 
+/// Dynamic Entry reusable by payload references
+#[derive(Clone, Debug)]
+#[repr(C)]
+pub struct ReusableDynamicEntry {
+    size_le: u64,
+    digest: [u8; 32],
+}
+
+impl ReusableDynamicEntry {
+    #[inline]
+    pub fn size(&self) -> u64 {
+        u64::from_le(self.size_le)
+    }
+
+    #[inline]
+    pub fn digest(&self) -> [u8; 32] {
+        self.digest
+    }
+}
+
+/// List of dynamic entries containing the data given by an offset range
+fn lookup_dynamic_entries(
+    index: &DynamicIndexReader,
+    range: Range<u64>,
+) -> Result<(Vec<ReusableDynamicEntry>, u64, u64), Error> {
+    let end_idx = index.index_count() - 1;
+    let chunk_end = index.chunk_end(end_idx);
+    let start = index.binary_search(0, 0, end_idx, chunk_end, range.start)?;
+    let mut end = start;
+    while end < end_idx {
+        if range.end < index.chunk_end(end) {
+            break;
+        }
+        end += 1;
+    }
+
+    let offset_first = if start == 0 {
+        0
+    } else {
+        index.chunk_end(start - 1)
+    };
+
+    let padding_start = range.start - offset_first;
+    let padding_end = index.chunk_end(end) - range.end;
+
+    let mut indices = Vec::new();
+    let mut prev_end = offset_first;
+    for dynamic_entry in &index.index()[start..end + 1] {
+        let size = dynamic_entry.end() - prev_end;
+        let reusable_dynamic_entry = ReusableDynamicEntry {
+            size_le: size.to_le(),
+            digest: dynamic_entry.digest(),
+        };
+        prev_end += size;
+        indices.push(reusable_dynamic_entry);
+    }
+
+    Ok((indices, padding_start, padding_end))
+}
+
 fn get_metadata(
     fd: RawFd,
     stat: &FileStat,
-- 
2.39.2