Simplify frontier_pos logic, fix XD3_TOOFARBACK assertion failure exposed through go/src/regtest.go (64bithash branch) testing

1 files changed, 3 insertions, 4 deletions

diff --git a/xdelta3/xdelta3.h b/xdelta3/xdelta3.h
index 11bbdb8..1aef6be 100644
--- a/xdelta3/xdelta3.h
+++ b/xdelta3/xdelta3.h
@@ -783,10 +783,9 @@ struct _xd3_source
   xoff_t              max_blkno;  /* Maximum block, if eof is known,
                                    * otherwise, equals frontier_blkno
                                    * (initially 0). */
-  xoff_t              frontier_blkno;  /* If eof is unknown, the next
-                                        * source position to be read.
-                                        * Otherwise, equal to
-                                        * max_blkno. */
+  xoff_t              frontier_pos;  /* The next source position to be
+                                      * read, equal to ((max_blkno+1)
+                                      * << shiftby) */
   usize_t             onlastblk;  /* Number of bytes on max_blkno */
   int                 eof_known;  /* Set to true when the first
                                    * partial block is read. */