Implement linear and power-of-two histograms: hist() and lhist() keywords.

This is built on top of maps which are currently built on top of RB-trees.
Improvements are welcome!  For example the use of a hashing table as pointed
by espie@.

The following one-liner produce an histogram of power-of-two values returned
by the read(2) syscall:

btrace 'syscall:read:return { @bytes = hist(retval); }'
^C
@bytes:
[0]               19 |@@@@@@@@@@@@@@@@@@@@@@@@@@                          |
[1]               26 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@                |
[1, 2)             1 |@                                                   |
[2, 4)            13 |@@@@@@@@@@@@@@@@@@                                  |
[4, 8)             4 |@@@@@                                               |
[8, 16)            3 |@@@@                                                |
[16, 32)           1 |@                                                   |
[32, 64)           8 |@@@@@@@@@@@                                         |
[64, 128)         14 |@@@@@@@@@@@@@@@@@@@                                 |
[128, 256)         7 |@@@@@@@@@                                           |
[256, 512)        37 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@|
[512, 1K)          1 |@                                                   |
[1K, 2K)          10 |@@@@@@@@@@@@@@                                      |
[2K, 4K)          11 |@@@@@@@@@@@@@@@                                     |
[8K, 16K)          1 |@                                                   |

1 files changed, 5 insertions, 2 deletions

diff --git a/usr.sbin/btrace/btrace.h b/usr.sbin/btrace/btrace.h
index 27f4de57843..cd9001a44d8 100644
--- a/usr.sbin/btrace/btrace.h
+++ b/usr.sbin/btrace/btrace.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: btrace.h,v 1.5 2020/07/04 10:16:15 mpi Exp $ */
+/*	$OpenBSD: btrace.h,v 1.6 2020/07/11 14:52:14 mpi Exp $ */
 
 /*
  * Copyright (c) 2019 - 2020 Martin Pieuchot <mpi@openbsd.org>
@@ -40,13 +40,16 @@ int			 kelf_snprintsym(char *, size_t, unsigned long);
 
 /* map.c */
 struct map;
+struct hist;
 void			 map_clear(struct map *);
 void			 map_delete(struct map *, const char *);
 struct bt_arg		*map_get(struct map *, const char *);
 struct map		*map_insert(struct map *, const char *, struct bt_arg *,
-			    long);
+			    struct dt_evt *);
 void			 map_print(struct map *, size_t, const char *);
 void			 map_zero(struct map *);
+struct hist		*hist_increment(struct hist *, const char *, long);
+void			 hist_print(struct hist *, const char *);
 
 /* printf.c */
 int			 stmt_printf(struct bt_stmt *, struct dt_evt *);