diff --git a/src/backup/data_blob.rs b/src/backup/data_blob.rs
index 215797a1..c2027c8a 100644
--- a/src/backup/data_blob.rs
+++ b/src/backup/data_blob.rs
@@ -7,6 +7,7 @@ const MAX_BLOB_SIZE: usize = 128*1024*1024;
 
 use super::*;
 
+
 /// Data blob binary storage format
 ///
 /// Data blobs store arbitrary binary data (< 128MB), and can be
@@ -20,23 +21,6 @@ pub struct DataBlob {
 
 impl DataBlob {
 
-    pub fn header_size(magic: &[u8; 8]) -> usize {
-        match magic {
-            &UNCOMPRESSED_CHUNK_MAGIC_1_0 => std::mem::size_of::<DataChunkHeader>(),
-            &COMPRESSED_CHUNK_MAGIC_1_0 => std::mem::size_of::<DataChunkHeader>(),
-            &ENCRYPTED_CHUNK_MAGIC_1_0 => std::mem::size_of::<EncryptedDataChunkHeader>(),
-            &ENCR_COMPR_CHUNK_MAGIC_1_0 => std::mem::size_of::<EncryptedDataChunkHeader>(),
-
-            &UNCOMPRESSED_BLOB_MAGIC_1_0 => std::mem::size_of::<DataBlobHeader>(),
-            &COMPRESSED_BLOB_MAGIC_1_0 => std::mem::size_of::<DataBlobHeader>(),
-            &ENCRYPTED_BLOB_MAGIC_1_0 => std::mem::size_of::<EncryptedDataBlobHeader>(),
-            &ENCR_COMPR_BLOB_MAGIC_1_0 => std::mem::size_of::<EncryptedDataBlobHeader>(),
-            &AUTHENTICATED_BLOB_MAGIC_1_0 => std::mem::size_of::<AuthenticatedDataBlobHeader>(),
-            &AUTH_COMPR_BLOB_MAGIC_1_0 => std::mem::size_of::<AuthenticatedDataBlobHeader>(),
-            _ => panic!("unknown blob magic"),
-        }
-    }
-
     /// accessor to raw_data field
     pub fn raw_data(&self) -> &[u8]  {
         &self.raw_data
@@ -67,7 +51,7 @@ impl DataBlob {
     /// compute the CRC32 checksum
     pub fn compute_crc(&self) -> u32 {
         let mut hasher = crc32fast::Hasher::new();
-        let start = Self::header_size(self.magic()); // start after HEAD
+        let start = header_size(self.magic()); // start after HEAD
         hasher.update(&self.raw_data[start..]);
         hasher.finalize()
     }
diff --git a/src/backup/file_formats.rs b/src/backup/file_formats.rs
index 2f32cc51..fedea26f 100644
--- a/src/backup/file_formats.rs
+++ b/src/backup/file_formats.rs
@@ -119,3 +119,23 @@ pub struct EncryptedDataChunkHeader {
     pub iv: [u8; 16],
     pub tag: [u8; 16],
 }
+
+/// Header size for different file types
+///
+/// Panics on unknown magic numbers.
+pub fn header_size(magic: &[u8; 8]) -> usize {
+    match magic {
+        &UNCOMPRESSED_CHUNK_MAGIC_1_0 => std::mem::size_of::<DataChunkHeader>(),
+        &COMPRESSED_CHUNK_MAGIC_1_0 => std::mem::size_of::<DataChunkHeader>(),
+        &ENCRYPTED_CHUNK_MAGIC_1_0 => std::mem::size_of::<EncryptedDataChunkHeader>(),
+        &ENCR_COMPR_CHUNK_MAGIC_1_0 => std::mem::size_of::<EncryptedDataChunkHeader>(),
+
+        &UNCOMPRESSED_BLOB_MAGIC_1_0 => std::mem::size_of::<DataBlobHeader>(),
+        &COMPRESSED_BLOB_MAGIC_1_0 => std::mem::size_of::<DataBlobHeader>(),
+        &ENCRYPTED_BLOB_MAGIC_1_0 => std::mem::size_of::<EncryptedDataBlobHeader>(),
+        &ENCR_COMPR_BLOB_MAGIC_1_0 => std::mem::size_of::<EncryptedDataBlobHeader>(),
+        &AUTHENTICATED_BLOB_MAGIC_1_0 => std::mem::size_of::<AuthenticatedDataBlobHeader>(),
+        &AUTH_COMPR_BLOB_MAGIC_1_0 => std::mem::size_of::<AuthenticatedDataBlobHeader>(),
+        _ => panic!("unknown blob magic"),
+    }
+}