diff --git a/sources/io.F90 b/sources/io.F90
index ed41564..1dec66a 100644
--- a/sources/io.F90
+++ b/sources/io.F90
@@ -2896,47 +2896,54 @@ module io
 !
 !   Arguments:
 !
-!     lun      - the file handler to write to;
-!     aname    - the file attribute name;
-!     bytes    - the file size in bytes;
-!     digest   - the digest of the file content;
-!     filename - the file name;
+!     lun               - the file handler to write to;
+!     aname             - the file attribute name;
+!     filename          - the file name;
+!     data_bytes        - the file size in bytes;
+!     data_digest       - the digest of the file content;
+!     compressed_bytes  - the size of the compressed data in bytes;
+!     compressed_digest - the digest of the compressed data;
 !
 !===============================================================================
 !
-  subroutine write_attribute_xml_file(lun, aname, filename, bytes, digest)
+  subroutine write_attribute_xml_file(lun, aname, filename,                    &
+                                      data_bytes, data_digest,                 &
+                                      compressed_bytes, compressed_digest)
 
     implicit none
 
 ! input and output arguments
 !
-    integer         , intent(in) :: lun
-    character(len=*), intent(in) :: aname, filename
-    integer(kind=8) , intent(in) :: bytes, digest
+    integer                   , intent(in) :: lun
+    character(len=*)          , intent(in) :: aname, filename
+    integer(kind=8)           , intent(in) :: data_bytes, data_digest
+    integer(kind=8) , optional, intent(in) :: compressed_bytes, compressed_digest
 
 ! local variables
 !
-    character(len=32) :: digest_string, bytes_string
-
-! local parameters
-!
-    character(len=*), parameter :: afmt = "('<Attribute" //                    &
-           " type=" // '"' // "',a,'" // '"' //                                &
-           " name=" // '"' // "',a,'" // '"' //                                &
-           " size=" // '"' // "',a,'" // '"' //                                &
-           " digest_type=" // '"' // "',a,'" // '"' //                         &
-           " digest=" // '"' // "',a,'" // '"' //                              &
-           ">',a,'</Attribute>')"
+    character(len=32)   :: digest_string, bytes_string
+    character(len=1024) :: string
 !
 !-------------------------------------------------------------------------------
 !
-    write(bytes_string,"(1i22)") bytes
-    write(digest_string,"(1z0.16)") digest
-    write(lun,afmt) "string", trim(adjustl(aname)),                            &
-                              trim(adjustl(bytes_string)),                     &
-                              "xxh64",                                         &
-                              trim(adjustl(digest_string)),                    &
-                              trim(adjustl(filename))
+    string = '<Attribute type="string" name="' // trim(adjustl(aname)) // '"'
+    write(bytes_string,"(1i22)") data_bytes
+    string = trim(string) // ' size="' // trim(adjustl(bytes_string)) // '"'
+    if (present(compressed_bytes)) then
+      write(bytes_string,"(1i22)") compressed_bytes
+      string = trim(string) // ' compressed_size="' //                         &
+                        trim(adjustl(bytes_string)) // '"'
+    end if
+    string = trim(string) // ' digest_type="xxh64"'
+    write(digest_string,"(1z0.16)") data_digest
+    string = trim(string) // ' digest="' // trim(adjustl(digest_string)) // '"'
+    if (present(compressed_digest)) then
+      write(digest_string,"(1z0.16)") compressed_digest
+      string = trim(string) // ' compressed_digest="' //                       &
+                         trim(adjustl(digest_string)) // '"'
+    end if
+    string = trim(string) // '>' // trim(adjustl(filename)) // '</Attribute>'
+    write(lun,'(a)') trim(adjustl(string))
 
 !-------------------------------------------------------------------------------
 !