Add Python bindings for testing local DBs

We just need to `dlopen("libpromises.so")` and then call the new
DB testing API functions with appropriate arguments.

Ticket: CFE-4281
Changelog: None

Author: vpodzime

.gitignore

@@ -52,6 +52,7 @@ stamp-h1
 /libpromises/Makefile
 /misc/Makefile
 /misc/selinux/Makefile
+/python/Makefile
 /tests/Makefile
 /tests/acceptance/25_cf-execd/Makefile
 /tests/acceptance/Makefile

Makefile.am

@@ -46,6 +46,7 @@ SUBDIRS = \
 	cf-net \
 	cf-secret \
 	misc \
+	python \
 	ext \
 	examples \
 	tests \

configure.ac

@@ -1872,6 +1872,7 @@ AC_CONFIG_FILES([Makefile
     contrib/vagrant-ci/centos-7-x64/Makefile
     misc/Makefile
     misc/selinux/Makefile
+    python/Makefile
     ext/Makefile
     examples/Makefile
     tests/Makefile

python/Makefile.am

@@ -0,0 +1,33 @@
+#
+#  Copyright 2024 Northern.tech AS
+#
+#  This file is part of CFEngine 3 - written and maintained by Northern.tech AS.
+#
+#  This program is free software; you can redistribute it and/or modify it
+#  under the terms of the GNU General Public License as published by the
+#  Free Software Foundation; version 3.
+#
+#  This program is distributed in the hope that it will be useful,
+#  but WITHOUT ANY WARRANTY; without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#  GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA
+#
+# To the extent this program is licensed as part of the Enterprise
+# versions of CFEngine, the applicable Commercial Open Source License
+# (COSL) may apply to this file if you as a licensee so wish it. See
+# included file COSL.txt.
+#
+
+pythonbindingsdir = $(libdir)/python
+dist_pythonbindings_DATA = README
+
+if !NDEBUG
+if LINUX
+# The dbm_test_api is only compile in on Linux in debug builds.
+dist_pythonbindings_DATA += test_cfe_db.py
+endif
+endif

python/README

@@ -0,0 +1,10 @@
+This directory contains Python packages and modules for working with CFEngine
+and its libraries.
+
+If you want to use one of these, PYTHONPATH and LD_LIBRARY_PATH variables can
+make things easier when used like this:
+
+  PYTHONPATH=/var/cfengine/lib/python LD_LIBRARY_PATH=/var/cfengine/lib python3
+
+That will make sure that the bindings are found by Python and that CFEngine's
+libraries are found by dlopen() (used by ctypes.CDLL() etc.).

python/test_cfe_db.py

@@ -0,0 +1,76 @@
+import ctypes
+
+# Based on the dbid enum from libpromises/dbm_api.h
+dbs = (
+    "classes",   # Deprecated
+    "variables", # Deprecated
+    "performance",
+    "checksums", # Deprecated
+    "filestats", # Deprecated
+    "changes",
+    "observations",
+    "state",
+    "lastseen",
+    "audit",
+    "locks",
+    "history",
+    "measure",
+    "static",
+    "scalars",
+    "windows_registry",
+    "cache",
+    "license",
+    "value",
+    "agent_execution",
+    "bundles",   # Deprecated
+    "packages_installed", # new package promise installed packages list
+    "packages_updates",   # new package promise list of available updates
+    "cookies", # Enterprise reporting cookies for duplicate host detection
+)
+
+def get_db_id(db_name):
+    return dbs.index(db_name)
+
+
+class _SimulationStruct(ctypes.Structure):
+    pass
+
+class _FilamentStruct(ctypes.Structure):
+    pass
+
+_promises = ctypes.CDLL("libpromises.so.3.0.6")
+
+_promises.SimulateDBLoad.restype = ctypes.POINTER(_SimulationStruct)
+_promises.SimulateDBLoad.argtypes = [ctypes.c_int, ctypes.c_int, ctypes.c_long, ctypes.c_long,
+                                     ctypes.c_int, ctypes.c_int, ctypes.c_long, ctypes.c_long,
+                                     ctypes.c_long, ctypes.c_long]
+def SimulateDBLoad(db_id,
+                   read_keys_refresh_s=5,
+                   read_min_interval_ms=100,
+                   read_max_interval_ms=200,
+                   write_sample_size_pct=50,
+                   write_prune_interval_s=10,
+                   write_min_interval_ms=200,
+                   write_max_interval_ms=400,
+                   iter_min_interval_ms=1000,
+                   iter_max_interval_ms=2000):
+    return _promises.SimulateDBLoad(db_id,
+                                    read_keys_refresh_s, read_min_interval_ms, read_max_interval_ms,
+                                    write_sample_size_pct,
+                                    write_prune_interval_s, write_min_interval_ms, write_max_interval_ms,
+                                    iter_min_interval_ms, iter_max_interval_ms)
+
+_promises.StopSimulation.restype = None # void
+_promises.StopSimulation.argtypes = [ctypes.POINTER(_SimulationStruct)]
+def StopSimulation(simulation):
+    _promises.StopSimulation(simulation)
+
+_promises.FillUpDB.restype = ctypes.POINTER(_FilamentStruct)
+_promises.FillUpDB.argtypes = [ctypes.c_int, ctypes.c_int]
+def FillUpDB(db_id, usage):
+    return _promises.FillUpDB(db_id, usage)
+
+_promises.RemoveFilament.restype = None # void
+_promises.RemoveFilament.argtypes = [ctypes.POINTER(_FilamentStruct)]
+def RemoveFilament(filament):
+    _promises.RemoveFilament(filament)