A simple cache of uid->uname lookups and gid->gname lookups eliminates

almost 1/2 of the CPU time required to create an uncompressed archive
and makes a noticable reduction in wallclock time.

1 files changed, 14 insertions, 0 deletions

diff --git a/usr.bin/tar/bsdtar.h b/usr.bin/tar/bsdtar.h
index dd37326..f11f451 100644
--- a/usr.bin/tar/bsdtar.h
+++ b/usr.bin/tar/bsdtar.h
@@ -77,6 +77,20 @@ struct bsdtar {
 
 	struct links_entry	*links_head;
 	struct archive_dir_entry *archive_dir_head, *archive_dir_tail;
+
+	/* An arbitrary prime number. */
+	#define bsdtar_hash_size 71
+	/* A simple hash of uid/uname for caching uname lookups. */
+	struct {
+		uid_t uid;
+		char *uname;
+	} uname_lookup[bsdtar_hash_size];
+
+	/* A simple hash of gid/gname for caching gname lookups. */
+	struct {
+		gid_t gid;
+		char *gname;
+	} gname_lookup[bsdtar_hash_size];
 };
 
 const char	*bsdtar_progname(void);