libzutil: allow to display powers of 1000 bytes

ZFS displays bytes with K/M/G/T/P/E prefixes. They represent powers of
1024 bytes, i.e. KiB, MiB, GiB, TiB, PiB, EiB.
Some users may want these prefixes to represent powers of 1000 bytes,
i.e. KB, MB, GB, TB, PB, EB.
This adds the new unit format and allows to use such display by
defining an environment variable.

Signed-off-by: Julien Cassette <jcassette@proton.me>

Author: jcassette

include/libzutil.h

@@ -144,13 +144,15 @@ _LIBZUTIL_H boolean_t zfs_isnumber(const char *);
  * ZFS_NICENUM_TIME:	Print nanosecs, microsecs, millisecs, seconds...
  * ZFS_NICENUM_RAW:	Print the raw number without any formatting
  * ZFS_NICENUM_RAWTIME:	Same as RAW, but print dashes ('-') for zero.
+ * ZFS_NICENUM_BYTES_1000: Same as ZFS_NICENUM_BYTES but use powers of 1000.
  */
 enum zfs_nicenum_format {
 	ZFS_NICENUM_1024 = 0,
 	ZFS_NICENUM_BYTES = 1,
 	ZFS_NICENUM_TIME = 2,
 	ZFS_NICENUM_RAW = 3,
-	ZFS_NICENUM_RAWTIME = 4
+	ZFS_NICENUM_RAWTIME = 4,
+	ZFS_NICENUM_BYTES_1000 = 5
 };
 
 /*

lib/libzutil/zutil_nicenum.c

@@ -26,6 +26,7 @@
 #include <ctype.h>
 #include <math.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <libzutil.h>
 #include <string.h>
 
@@ -64,19 +65,22 @@ zfs_nicenum_format(uint64_t num, char *buf, size_t buflen,
 	uint64_t n = num;
 	int index = 0;
 	const char *u;
-	const char *units[3][7] = {
+	const char *units[5][7] = {
 	    [ZFS_NICENUM_1024] = {"", "K", "M", "G", "T", "P", "E"},
 	    [ZFS_NICENUM_BYTES] = {"B", "K", "M", "G", "T", "P", "E"},
-	    [ZFS_NICENUM_TIME] = {"ns", "us", "ms", "s", "?", "?", "?"}
+	    [ZFS_NICENUM_TIME] = {"ns", "us", "ms", "s", "?", "?", "?"},
+	    [ZFS_NICENUM_BYTES_1000] = {"B", "K", "M", "G", "T", "P", "E"}
 	};
 
 	const int units_len[] = {[ZFS_NICENUM_1024] = 6,
 	    [ZFS_NICENUM_BYTES] = 6,
-	    [ZFS_NICENUM_TIME] = 4};
+	    [ZFS_NICENUM_TIME] = 4,
+	    [ZFS_NICENUM_BYTES_1000] = 6};
 
 	const int k_unit[] = {	[ZFS_NICENUM_1024] = 1024,
 	    [ZFS_NICENUM_BYTES] = 1024,
-	    [ZFS_NICENUM_TIME] = 1000};
+	    [ZFS_NICENUM_TIME] = 1000,
+	    [ZFS_NICENUM_BYTES_1000] = 1000};
 
 	double val;
 
@@ -180,5 +184,9 @@ zfs_niceraw(uint64_t num, char *buf, size_t buflen)
 void
 zfs_nicebytes(uint64_t num, char *buf, size_t buflen)
 {
-	zfs_nicenum_format(num, buf, buflen, ZFS_NICENUM_BYTES);
+	if (getenv("ZFS_KB_IS_1000") != NULL) {
+		zfs_nicenum_format(num, buf, buflen, ZFS_NICENUM_BYTES_1000);
+	} else {
+		zfs_nicenum_format(num, buf, buflen, ZFS_NICENUM_BYTES);
+	}
 }