Support ZFS ARC stats on FreeBSD

New meter displays same ARC stats as FreeBSD top(1).
Can be extended to other platforms that support ZFS.

Pulling kstat.zfs.misc.arcstats.c_max as the meter
total, so the meter has a meaningful value to work
up to.

The Text meter displays, first, the maximum
ARC size (Meter.total), then second, the total
ARC used, using the difference between Meter.maxItems
and Meter.curItems to "hide" the used value from the
Bar and Graph drawing functions by using an index
in Meter.values[] that is beyond curItems - 1, but
less than maxItems - 1.

zfs/ZfsArcMeter.c

@@ -0,0 +1,81 @@
+/*
+htop - ZfsArcMeter.c
+(C) 2004-2011 Hisham H. Muhammad
+Released under the GNU GPL, see the COPYING file
+in the source distribution for its full text.
+*/
+
+#include "ZfsArcMeter.h"
+
+#include "CRT.h"
+#include "Platform.h"
+
+#include <stdlib.h>
+#include <string.h>
+#include <math.h>
+#include <sys/param.h>
+#include <assert.h>
+
+/*{
+#include "Meter.h"
+}*/
+
+int ZfsArcMeter_attributes[] = {
+   ZFS_MFU, ZFS_MRU, ZFS_ANON, ZFS_HEADER, ZFS_OTHER
+};
+
+static void ZfsArcMeter_updateValues(Meter* this, char* buffer, int size) {
+   int written;
+   Platform_setZfsArcValues(this);
+
+   written = Meter_humanUnit(buffer, this->values[5], size);
+   buffer += written;
+   if ((size -= written) > 0) {
+      *buffer++ = '/';
+      size--;
+      Meter_humanUnit(buffer, this->total, size);
+   }
+}
+
+static void ZfsArcMeter_display(Object* cast, RichString* out) {
+   char buffer[50];
+   Meter* this = (Meter*)cast;
+
+   RichString_write(out, CRT_colors[METER_TEXT], ":");
+   Meter_humanUnit(buffer, this->total, 50);
+   RichString_append(out, CRT_colors[METER_VALUE], buffer);
+   Meter_humanUnit(buffer, this->values[5], 50);
+   RichString_append(out, CRT_colors[METER_TEXT], " Used:");
+   RichString_append(out, CRT_colors[METER_VALUE], buffer);
+   Meter_humanUnit(buffer, this->values[0], 50);
+   RichString_append(out, CRT_colors[METER_TEXT], " MFU:");
+   RichString_append(out, CRT_colors[ZFS_MFU], buffer);
+   Meter_humanUnit(buffer, this->values[1], 50);
+   RichString_append(out, CRT_colors[METER_TEXT], " MRU:");
+   RichString_append(out, CRT_colors[ZFS_MRU], buffer);
+   Meter_humanUnit(buffer, this->values[2], 50);
+   RichString_append(out, CRT_colors[METER_TEXT], " Anon:");
+   RichString_append(out, CRT_colors[ZFS_ANON], buffer);
+   Meter_humanUnit(buffer, this->values[3], 50);
+   RichString_append(out, CRT_colors[METER_TEXT], " Hdr:");
+   RichString_append(out, CRT_colors[ZFS_HEADER], buffer);
+   Meter_humanUnit(buffer, this->values[4], 50);
+   RichString_append(out, CRT_colors[METER_TEXT], " Oth:");
+   RichString_append(out, CRT_colors[ZFS_OTHER], buffer);
+}
+
+MeterClass ZfsArcMeter_class = {
+   .super = {
+      .extends = Class(Meter),
+      .delete = Meter_delete,
+      .display = ZfsArcMeter_display,
+   },
+   .updateValues = ZfsArcMeter_updateValues, 
+   .defaultMode = TEXT_METERMODE,
+   .maxItems = 6,
+   .total = 100.0,
+   .attributes = ZfsArcMeter_attributes,
+   .name = "ZFSARC",
+   .uiName = "ZFS ARC",
+   .caption = "ARC"
+};

zfs/ZfsArcMeter.h

@@ -0,0 +1,18 @@
+/* Do not edit this file. It was automatically generated. */
+
+#ifndef HEADER_ZfsArcMeter
+#define HEADER_ZfsArcMeter
+/*
+htop - ZfsArcMeter.h
+(C) 2004-2011 Hisham H. Muhammad
+Released under the GNU GPL, see the COPYING file
+in the source distribution for its full text.
+*/
+
+#include "Meter.h"
+
+extern int ZfsArcMeter_attributes[];
+
+extern MeterClass ZfsArcMeter_class;
+
+#endif