Add helper fn to create shared buffer - simplify archive format matching (#26674)

runtime/src/snapshot_utils.rs

@@ -1492,15 +1492,13 @@ pub fn purge_old_snapshot_archives(
     }
 }
 
-fn unpack_snapshot_local<T: 'static + Read + std::marker::Send, F: Fn() -> T>(
-    reader: F,
+fn unpack_snapshot_local(
+    shared_buffer: SharedBuffer,
     ledger_dir: &Path,
     account_paths: &[PathBuf],
     parallel_divisions: usize,
 ) -> Result<UnpackedAppendVecMap> {
     assert!(parallel_divisions > 0);
-    // a shared 'reader' that reads the decompressed stream once, keeps some history, and acts as a reader for multiple parallel archive readers
-    let shared_buffer = SharedBuffer::new(reader());
 
     // allocate all readers before any readers start reading
     let readers = (0..parallel_divisions)
@@ -1530,47 +1528,22 @@ fn unpack_snapshot_local<T: 'static + Read + std::marker::Send, F: Fn() -> T>(
     Ok(unpacked_append_vec_map)
 }
 
-fn untar_snapshot_file(
+fn untar_snapshot_create_shared_buffer(
     snapshot_tar: &Path,
-    unpack_dir: &Path,
-    account_paths: &[PathBuf],
     archive_format: ArchiveFormat,
-    parallel_divisions: usize,
-) -> Result<UnpackedAppendVecMap> {
+) -> Result<SharedBuffer> {
     let open_file = || File::open(&snapshot_tar).unwrap();
-    let account_paths_map = match archive_format {
-        ArchiveFormat::TarBzip2 => unpack_snapshot_local(
-            || BzDecoder::new(BufReader::new(open_file())),
-            unpack_dir,
-            account_paths,
-            parallel_divisions,
-        )?,
-        ArchiveFormat::TarGzip => unpack_snapshot_local(
-            || GzDecoder::new(BufReader::new(open_file())),
-            unpack_dir,
-            account_paths,
-            parallel_divisions,
-        )?,
-        ArchiveFormat::TarZstd => unpack_snapshot_local(
-            || zstd::stream::read::Decoder::new(BufReader::new(open_file())).unwrap(),
-            unpack_dir,
-            account_paths,
-            parallel_divisions,
-        )?,
-        ArchiveFormat::TarLz4 => unpack_snapshot_local(
-            || lz4::Decoder::new(BufReader::new(open_file())).unwrap(),
-            unpack_dir,
-            account_paths,
-            parallel_divisions,
-        )?,
-        ArchiveFormat::Tar => unpack_snapshot_local(
-            || BufReader::new(open_file()),
-            unpack_dir,
-            account_paths,
-            parallel_divisions,
-        )?,
-    };
-    Ok(account_paths_map)
+    Ok(match archive_format {
+        ArchiveFormat::TarBzip2 => SharedBuffer::new(BzDecoder::new(BufReader::new(open_file()))),
+        ArchiveFormat::TarGzip => SharedBuffer::new(GzDecoder::new(BufReader::new(open_file()))),
+        ArchiveFormat::TarZstd => SharedBuffer::new(
+            zstd::stream::read::Decoder::new(BufReader::new(open_file())).unwrap(),
+        ),
+        ArchiveFormat::TarLz4 => {
+            SharedBuffer::new(lz4::Decoder::new(BufReader::new(open_file())).unwrap())
+        }
+        ArchiveFormat::Tar => SharedBuffer::new(BufReader::new(open_file())),
+    })
 }
 
 fn untar_snapshot_in<P: AsRef<Path>>(
@@ -1580,13 +1553,8 @@ fn untar_snapshot_in<P: AsRef<Path>>(
     archive_format: ArchiveFormat,
     parallel_divisions: usize,
 ) -> Result<UnpackedAppendVecMap> {
-    untar_snapshot_file(
-        snapshot_tar.as_ref(),
-        unpack_dir,
-        account_paths,
-        archive_format,
-        parallel_divisions,
-    )
+    let shared_buffer = untar_snapshot_create_shared_buffer(snapshot_tar.as_ref(), archive_format)?;
+    unpack_snapshot_local(shared_buffer, unpack_dir, account_paths, parallel_divisions)
 }
 
 fn verify_unpacked_snapshots_dir_and_version(