[PATCH v6 proxmox-backup 05/18] datastore: combine public FixedIndexWriter methods into add_chunk

[Robert Obkircher <r.obkircher@proxmox.com>]

These operations were always performed together anyway, so it makes
sense to simplify the public api.

Signed-off-by: Robert Obkircher <r.obkircher@proxmox.com>
---
 pbs-datastore/src/fixed_index.rs | 17 +++++++++++++++--
 src/api2/backup/environment.rs   |  5 +----
 2 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/pbs-datastore/src/fixed_index.rs b/pbs-datastore/src/fixed_index.rs
index becbe3e3..081dc51f 100644
--- a/pbs-datastore/src/fixed_index.rs
+++ b/pbs-datastore/src/fixed_index.rs
@@ -351,7 +351,7 @@ impl FixedIndexWriter {
         Ok(index_csum)
     }
 
-    pub fn check_chunk_alignment(&self, offset: usize, chunk_len: usize) -> Result<usize, Error> {
+    fn check_chunk_alignment(&self, offset: usize, chunk_len: usize) -> Result<usize, Error> {
         if offset < chunk_len {
             bail!("got chunk with small offset ({} < {}", offset, chunk_len);
         }
@@ -381,7 +381,7 @@ impl FixedIndexWriter {
         Ok(pos / self.chunk_size)
     }
 
-    pub fn add_digest(&mut self, index: usize, digest: &[u8; 32]) -> Result<(), Error> {
+    fn add_digest(&mut self, index: usize, digest: &[u8; 32]) -> Result<(), Error> {
         if index >= self.index_length {
             bail!(
                 "add digest failed - index out of range ({} >= {})",
@@ -403,6 +403,19 @@ impl FixedIndexWriter {
         Ok(())
     }
 
+    /// Write the digest of a chunk into this index file.
+    ///
+    /// The `start` and `size` parameters encode the range of
+    /// content that is backed up. It is verified that `start` is
+    /// aligned and that only the last chunk may be smaller.
+    pub fn add_chunk(&mut self, start: u64, size: u32, digest: &[u8; 32]) -> Result<(), Error> {
+        let Some(end) = start.checked_add(size.into()) else {
+            bail!("add_chunk: start and size are too large: {start}+{size}");
+        };
+        let idx = self.check_chunk_alignment(end as usize, size as usize)?;
+        self.add_digest(idx, digest)
+    }
+
     pub fn clone_data_from(&mut self, reader: &FixedIndexReader) -> Result<(), Error> {
         if self.index_length != reader.index_count() {
             bail!("clone_data_from failed - index sizes not equal");
diff --git a/src/api2/backup/environment.rs b/src/api2/backup/environment.rs
index bd9c5211..517f698e 100644
--- a/src/api2/backup/environment.rs
+++ b/src/api2/backup/environment.rs
@@ -442,13 +442,10 @@ impl BackupEnvironment {
             );
         }
 
-        let end = (offset as usize) + (size as usize);
-        let idx = data.index.check_chunk_alignment(end, size as usize)?;
+        data.index.add_chunk(offset, size, digest)?;
 
         data.chunk_count += 1;
 
-        data.index.add_digest(idx, digest)?;
-
         Ok(())
     }
 
-- 
2.47.3