PCP: support for 'dynamic columns' added at runtime

Implements support for arbitrary Performance Co-Pilot
metrics with per-process instance domains to form new
htop columns.  The column-to-metric mappings are setup
using configuration files which will be documented via
man pages as part of a follow-up commit.

We provide an initial set of column configurations so
as to provide new capabilities to pcp-htop: including
configs for containers, open fd counts, scheduler run
queue time, tcp/udp bytes/calls sent/recv, delay acct,
virtual machine guests, detailed virtual memory, swap.

Note there is a change to the configuration file path
resolution algorithm introduced for 'dynamic meters'.
First, look in any custom PCP_HTOP_DIR location.  Then
iterate, in priority order, users home directory, then
local sysadmins files in /etc/pcp/htop, then readonly
configuration files below /usr/share/pcp/htop.  This
final location becomes the preferred place for our own
shipped meter and column files.

The Settings file (htoprc) writing code is updated to
not using the numeric identifier for dynamic columns.
The same strategy used for dynamic meters is used here
where we write Dynamic(name) so the name can be setup
once more at start.  Regular (static) columns writing
to htoprc - i.e. numerically indexed - is unchanged.

1 files changed, 60 insertions, 0 deletions

diff --git a/DynamicColumn.c b/DynamicColumn.c
new file mode 100644
index 00000000..62b38238
--- /dev/null
+++ b/DynamicColumn.c
@@ -0,0 +1,60 @@
+/*
+htop - DynamicColumn.c
+(C) 2021 Sohaib Mohammed
+(C) 2021 htop dev team
+(C) 2021 Red Hat, Inc.  All Rights Reserved.
+Released under the GNU GPLv2, see the COPYING file
+in the source distribution for its full text.
+*/
+
+#include "config.h" // IWYU pragma: keep
+
+#include "DynamicColumn.h"
+
+#include <stddef.h>
+
+#include "Platform.h"
+#include "ProcessList.h"
+#include "RichString.h"
+#include "XUtils.h"
+
+
+Hashtable* DynamicColumns_new(void) {
+   return Platform_dynamicColumns();
+}
+
+const char* DynamicColumn_init(unsigned int key) {
+   return Platform_dynamicColumnInit(key);
+}
+
+typedef struct {
+   const char* name;
+   const DynamicColumn* data;
+   unsigned int key;
+} DynamicIterator;
+
+static void DynamicColumn_compare(ht_key_t key, void* value, void* data) {
+   const DynamicColumn* column = (const DynamicColumn*)value;
+   DynamicIterator* iter = (DynamicIterator*)data;
+   if (String_eq(iter->name, column->name)) {
+      iter->data = column;
+      iter->key = key;
+   }
+}
+
+const DynamicColumn* DynamicColumn_search(Hashtable* dynamics, const char* name, unsigned int* key) {
+   DynamicIterator iter = { .key = 0, .data = NULL, .name = name };
+   if (dynamics)
+      Hashtable_foreach(dynamics, DynamicColumn_compare, &iter);
+   if (key)
+      *key = iter.key;
+   return iter.data;
+}
+
+const DynamicColumn* DynamicColumn_lookup(Hashtable* dynamics, unsigned int key) {
+   return (const DynamicColumn*) Hashtable_get(dynamics, key);
+}
+
+bool DynamicColumn_writeField(const Process* proc, RichString* str, unsigned int key) {
+   return Platform_dynamicColumnWriteField(proc, str, key);
+}