From 87617b9ae63c4675460244d067e246b362dc3867 Mon Sep 17 00:00:00 2001 From: Mads Ynddal Date: Tue, 26 Sep 2023 12:34:30 +0200 Subject: [PATCH] simpletrace: made Analyzer into context-manager Instead of explicitly calling `begin` and `end`, we can change the class to use the context-manager paradigm. This is mostly a styling choice, used in modern Python code. But it also allows for more advanced analyzers to handle exceptions gracefully in the `__exit__` method (not demonstrated here). Reviewed-by: Stefan Hajnoczi Signed-off-by: Mads Ynddal Message-id: 20230926103436.25700-9-mads@ynddal.dk Signed-off-by: Stefan Hajnoczi --- scripts/simpletrace.py | 31 ++++++++++++++++++++----------- 1 file changed, 20 insertions(+), 11 deletions(-) diff --git a/scripts/simpletrace.py b/scripts/simpletrace.py index 229b10aa99..7f514d1577 100755 --- a/scripts/simpletrace.py +++ b/scripts/simpletrace.py @@ -122,12 +122,13 @@ def read_trace_records(event_mapping, event_id_to_name, fobj): yield rec -class Analyzer(object): +class Analyzer: """A trace file analyzer which processes trace records. An analyzer can be passed to run() or process(). The begin() method is invoked, then each trace record is processed, and finally the end() method - is invoked. + is invoked. When Analyzer is used as a context-manager (using the `with` + statement), begin() and end() are called automatically. If a method matching a trace event name exists, it is invoked to process that trace record. Otherwise the catchall() method is invoked. @@ -165,6 +166,15 @@ def end(self): """Called at the end of the trace.""" pass + def __enter__(self): + self.begin() + return self + + def __exit__(self, exc_type, exc_val, exc_tb): + if exc_type is None: + self.end() + return False + def process(events, log, analyzer, read_header=True): """Invoke an analyzer on each event in a log. Args: @@ -226,15 +236,14 @@ def build_fn(analyzer, event): # Just arguments, no timestamp or pid return lambda _, rec: fn(*rec[3:3 + event_argcount]) - analyzer.begin() - fn_cache = {} - for rec in read_trace_records(event_mapping, event_id_to_name, log): - event_num = rec[0] - event = event_mapping[event_num] - if event_num not in fn_cache: - fn_cache[event_num] = build_fn(analyzer, event) - fn_cache[event_num](event, rec) - analyzer.end() + with analyzer: + fn_cache = {} + for rec in read_trace_records(event_mapping, event_id_to_name, log): + event_num = rec[0] + event = event_mapping[event_num] + if event_num not in fn_cache: + fn_cache[event_num] = build_fn(analyzer, event) + fn_cache[event_num](event, rec) if close_log: log.close()