Add a new DynamicMeter class for runtime Meter extension

This commit is based on exploratory work by Sohaib Mohamed.
The end goal is two-fold - to support addition of Meters we
build via configuration files for both the PCP platform and
for scripts ( https://github.com/htop-dev/htop/issues/526 )

Here, we focus on generic code and the PCP support.  A new
class DynamicMeter is introduced - it uses the special case
'param' field handling that previously was used only by the
CPUMeter, such that every runtime-configured Meter is given
a unique identifier.  Unlike with the CPUMeter this is used
internally only.  When reading/writing to htoprc instead of
CPU(N) - where N is an integer param (CPU number) - we use
the string name for each meter.  For example, if we have a
configuration for a DynamicMeter for some Redis metrics, we
might read and write "Dynamic(redis)".  This identifier is
subsequently matched (back) up to the configuration file so
we're able to re-create arbitrary user configurations.

The PCP platform configuration file format is fairly simple.
We expand configs from several directories, including the
users homedir alongside htoprc (below htop/meters/) and also
/etc/pcp/htop/meters.  The format will be described via a
new pcp-htop(5) man page, but its basically ini-style and
each Meter has one or more metric expressions associated, as
well as specifications for labels, color and so on via a dot
separated notation for individual metrics within the Meter.

A few initial sample configuration files are provided below
./pcp/meters that give the general idea.  The PCP "derived"
metric specification - see pmRegisterDerived(3) - is used
as the syntax for specifying metrics in PCP DynamicMeters.

3 files changed, 11 insertions, 3 deletions

diff --git a/openbsd/OpenBSDProcessList.c b/openbsd/OpenBSDProcessList.c
index c9b1db7a..8dc4ac94 100644
--- a/openbsd/OpenBSDProcessList.c
+++ b/openbsd/OpenBSDProcessList.c
@@ -36,7 +36,7 @@ static long fscale;
 static int pageSize;
 static int pageSizeKB;
 
-ProcessList* ProcessList_new(UsersTable* usersTable, Hashtable* pidMatchList, uid_t userId) {
+ProcessList* ProcessList_new(UsersTable* usersTable, Hashtable* dynamicMeters, Hashtable* pidMatchList, uid_t userId) {
    const int nmib[] = { CTL_HW, HW_NCPU };
    const int mib[] = { CTL_HW, HW_NCPUONLINE };
    const int fmib[] = { CTL_KERN, KERN_FSCALE };
@@ -48,7 +48,7 @@ ProcessList* ProcessList_new(UsersTable* usersTable, Hashtable* pidMatchList, ui
 
    OpenBSDProcessList* opl = xCalloc(1, sizeof(OpenBSDProcessList));
    ProcessList* pl = (ProcessList*) opl;
-   ProcessList_init(pl, Class(OpenBSDProcess), usersTable, pidMatchList, userId);
+   ProcessList_init(pl, Class(OpenBSDProcess), usersTable, dynamicMeters, pidMatchList, userId);
 
    size = sizeof(pl->cpuCount);
    r = sysctl(mib, 2, &pl->cpuCount, &size, NULL, 0);
diff --git a/openbsd/OpenBSDProcessList.h b/openbsd/OpenBSDProcessList.h
index 0ef6a894..5734d3ab 100644
--- a/openbsd/OpenBSDProcessList.h
+++ b/openbsd/OpenBSDProcessList.h
@@ -49,7 +49,7 @@ typedef struct OpenBSDProcessList_ {
 } OpenBSDProcessList;
 
 
-ProcessList* ProcessList_new(UsersTable* usersTable, Hashtable* pidMatchList, uid_t userId);
+ProcessList* ProcessList_new(UsersTable* usersTable, Hashtable* dynamicMeters, Hashtable* pidMatchList, uid_t userId);
 
 void ProcessList_delete(ProcessList* this);
 
diff --git a/openbsd/Platform.h b/openbsd/Platform.h
index 18e1a1c0..1c5e01c9 100644
--- a/openbsd/Platform.h
+++ b/openbsd/Platform.h
@@ -87,4 +87,12 @@ static inline void Platform_gettime_monotonic(uint64_t* msec) {
     Generic_gettime_monotonic(msec);
 }
 
+static inline Hashtable* Platform_dynamicMeters(void) { return NULL; }
+
+static inline void Platform_dynamicMeterInit(ATTR_UNUSED Meter* meter) { }
+
+static inline void Platform_dynamicMeterUpdateValues(ATTR_UNUSED Meter* meter) { }
+
+static inline void Platform_dynamicMeterDisplay(ATTR_UNUSED const Meter* meter, ATTR_UNUSED RichString* out) { }
+
 #endif