* src/sort.c: Avoid O(N**2) behavior when there are many temporary files.

Fix a race condition.

diff --git a/ChangeLog b/ChangeLog
index fb6522edb6595c2975c3a2924fe54987d0ae7099..bca8e7880eac159c30bb5d8c44b2d9420d0c85f5 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -2,7 +2,29 @@
 
        * Version 5.3.0.
 
-       * NEWS: Document the following change.
+       * NEWS: Document the following changes.
+
+       * src/sort.c: Avoid O(N**2) behavior when there are many temporary
+       files.
+       (temptail): New variable, so that we can easily append to list.
+       (create_temp_file): Create new files at end of list, so that
+       searching the list has O(N*NMERGE) behavior instead of O(N**2).
+       (zaptemp): Update temptail if needed.
+       (mergefps, merge): Accept new arg that counts temp files, and keep it
+       up to date as we create and remove temporaries.  This is for
+       efficiency, so that we don't call zaptemp so often.
+       All callers changed.
+       (sort): Don't create array in reverse order, since the list of
+       temporaries is now in the correct order.
+
+       (zaptemp): Protect against race condition: if 'sort' is
+       interrupted in the middle of zaptemp, it might unlink the
+       temporary file twice, and the second time this happens the file
+       might already have been created by some other process.
+
+       (create_temp_file): Use offsetof for clarity.
+       (die): Move it up earlier, to clean up the code a bit.
+
        * src/pr.c (strtoumax): Declare if not declared.
        (skip_to_page, first_page_number, last_page_number, page_number,
        first_last_page, print_header):