passwd: Cache the user/group tables

This is a significant optimization for conditions that need these
tables:

    Benchmark #1: ./bfs ~/code/linux -nouser >/dev/null
      Time (mean ± σ):     232.0 ms ±   2.5 ms    [User: 44.3 ms, System: 185.0 ms]
      Range (min … max):   228.7 ms … 238.7 ms    12 runs

    Benchmark #2: ./bfs-1.6 ~/code/linux -nouser >/dev/null
      Time (mean ± σ):      1.050 s ±  0.012 s    [User: 544.2 ms, System: 500.0 ms]
      Range (min … max):    1.025 s …  1.063 s    10 runs

    Benchmark #3: find ~/code/linux -nouser >/dev/null
      Time (mean ± σ):      1.040 s ±  0.012 s    [User: 533.6 ms, System: 500.6 ms]
      Range (min … max):    1.017 s …  1.054 s    10 runs

    Summary
      './bfs ~/code/linux -nouser >/dev/null' ran
        4.48 ± 0.07 times faster than 'find ~/code/linux -nouser >/dev/null'
        4.52 ± 0.07 times faster than './bfs-1.6 ~/code/linux -nouser >/dev/null'

1 files changed, 9 insertions, 0 deletions

diff --git a/cmdline.h b/cmdline.h
index 6670696..422fc6c 100644
--- a/cmdline.h
+++ b/cmdline.h
@@ -63,6 +63,15 @@ struct cmdline {
 	/** Colored stderr. */
 	CFILE *cerr;
 
+	/** User table. */
+	struct bfs_users *users;
+	/** The error that occurred parsing the user table, if any. */
+	int users_error;
+	/** Group table. */
+	struct bfs_groups *groups;
+	/** The error that occurred parsing the group table, if any. */
+	int groups_error;
+
 	/** Table of mounted file systems. */
 	struct bfs_mtab *mtab;
 	/** The error that occurred parsing the mount table, if any. */