[PATCH]: Optimize merge_file_trivial() (Was: Fix issue #4128)

Hi, all, Von: Philip Martin [philip.martin@wandisco.com] >> [Context: merge_file_trivial() in merge.c] > > I wonder if we could reduce the file IO by comparing all three files in > one operation instead of two operations on pairs of files? In follow-up to my last patch fixing issue #4128, the following patch optimizes merge_file_trivial(). It avoids reading the files twice by using a new comparison function which compares 3 files at once. Open issues (AFAICS): - The naming of the functions. (I did use the word three instead of the cipher 3 to avoid confusion with revisioned APIs.) - The order of parameters. I'm not sure whether 12,23,13 is more natural, or 12,13,23. Summary of test results: 1618 tests PASSED 85 tests SKIPPED 39 tests XFAILED (1 WORK-IN-PROGRESS) [[ Optimize merge_file_trivial() by avoiding to read the files twice by using a new comparison function which compares 3 files at once. * subversion/include/svn_io.h (svn_io_filesizes_three_different_p): Add new declaration (svn_io_files_contents_three_same_p): Add new declaration * subversion/libsvn_subr/io.c (svn_io_filesizes_three_different_p): Add new function in analogy to svn_io_filesizes_different_p(). (contents_three_identical_p): Add new function in analogy to contents_identical_p(). (svn_io_files_contents_three_same_p): Add new function in analogy to svn_io_files_contents_same_p. * subversion/libsvn_wc/merge.c (merge_file_trivial): Use the new three-file comparison functions to avoid reading files twice. Patch by: Markus Schaber <m.schaber@3s-software.com> ]] Thank you, Markus Schaber -- We software Automation. 3S-Smart Software Solutions GmbH Markus Schaber | Developer Memminger Str. 151 | 87439 Kempten | Germany | Tel. +49-831-54031-0 | Fax +49-831-54031-50 Email: m.schaber@3s-software.com | Web: http://www.3s-software.com CoDeSys internet forum: http://forum.3s-software.com Download CoDeSys sample projects: http://www.3s-software.com/index.shtml?sample_projects Managing Directors: Dipl.Inf. Dieter Hess, Dipl.Inf. Manfred Werner | Trade register: Kempten HRB 6186 | Tax ID No.: DE 167014915