lib.log: Add module

A dedicated logging module is currently provided by jw-python, but
since it's often needed also in jw-pkg, and it's relatively small and
maintainable, it seems justified to move it into jw-pkg.

Signed-off-by: Jan Lindemann <jan@janware.com>

src/python/jw/pkg/lib/log.py

@@ -0,0 +1,78 @@
+# -*- coding: utf-8 -*-
+
+import sys, syslog, datetime
+
+EMERG                = int(syslog.LOG_EMERG)
+ALERT                = int(syslog.LOG_ALERT)
+CRIT                 = int(syslog.LOG_CRIT)
+ERR                  = int(syslog.LOG_ERR)
+WARNING              = int(syslog.LOG_WARNING)
+NOTICE               = int(syslog.LOG_NOTICE)
+INFO                 = int(syslog.LOG_INFO)
+DEBUG                = int(syslog.LOG_DEBUG)
+DEVEL                = int(syslog.LOG_DEBUG + 1)
+OFF                  = DEVEL + 1
+
+_log_level           = NOTICE
+_last_tstamp         = datetime.datetime.now()
+_first_tstamp        = _last_tstamp
+
+def _log_level_name_by_value():
+    if _log_level_name_by_value.map is None:
+        _log_level_name_by_value.map = {
+            EMERG: "EMERG",
+            ALERT: "ALERT",
+            CRIT: "CRIT",
+            ERR: "ERR",
+            WARNING: "WARNING",
+            NOTICE: "NOTICE",
+            INFO: "INFO",
+            DEBUG: "DEBUG",
+            DEVEL: "DEVEL",
+            OFF: "OFF"
+        }
+    return _log_level_name_by_value.map
+_log_level_name_by_value.map: dict[int, str]|None = None
+
+def _log_level_value_by_name():
+    if _log_level_value_by_name.map is None:
+        _log_level_value_by_name.map = {}
+        for value, name in _log_level_name_by_value().items():
+            _log_level_value_by_name.map[name] = value
+            _log_level_value_by_name.map[name.lower()] = value
+    return _log_level_value_by_name.map
+_log_level_value_by_name.map: dict[str, int]|None = None
+
+def get_log_level_name(level: int) -> str:
+    return _log_level_name_by_value()[level]
+
+def parse_log_level(level: str|int) -> int:
+    try:
+        ret = int(level)
+        if ret >= 0 and ret <= DEVEL:
+            return ret
+    except ValueError:
+       return _log_level_value_by_name()[level]
+    raise Exception("Invalid log level ", level)
+
+def set_log_level(level: int|None=None) -> int:
+    global _log_level
+    ret = _log_level
+    if level is not None:
+        _log_level = parse_log_level(level)
+    return ret
+
+def set_log_flags(*args, **kwargs):
+    pass
+
+def log(prio: int, *args, **kwargs):
+    global _log_level
+    if prio > _log_level:
+        return
+    print(*args, file = sys.stderr)
+
+def log_time_diff(prio: int, *args, **kwargs):
+    global _last_tstamp
+    now = datetime.datetime.now()
+    log(prio, now - _last_tstamp, now - _first_tstamp, *args)
+    _last_tstamp = now