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"""Raw data collector for coverage.py."""
import sys, threading
try:
# Use the C extension code when we can, for speed.
from coverage.tracer import Tracer
except ImportError:
# If we don't have the C tracer, use this Python one.
class Tracer:
"""Python implementation of the raw data tracer."""
def __init__(self):
self.cur_filename = None
self.filename_stack = []
def _global_trace(self, frame, event, arg_unused):
"""The trace function passed to sys.settrace."""
if event == 'call':
filename = frame.f_code.co_filename
tracename = self.should_trace_cache.get(filename)
if tracename is None:
tracename = self.should_trace(filename)
self.should_trace_cache[filename] = tracename
if tracename:
self.filename_stack.append(self.cur_filename)
self.cur_filename = tracename
return self._local_trace
else:
return None
return self.trace
def _local_trace(self, frame, event, arg_unused):
if event == 'line':
self.data[(self.cur_filename, frame.f_lineno)] = True
elif event == 'return':
self.cur_filename = self.filename_stack.pop()
return self._local_trace
def start(self):
sys.settrace(self._global_trace)
def stop(self):
sys.settrace(None)
class Collector:
"""Collects trace data.
Creates a Tracer object for each thread, since they track stack information.
Each Tracer points to the same shared data, contributing traced data points.
"""
def __init__(self, should_trace):
"""Create a collector.
`should_trace` is a function, taking a filename, and returns a
canonicalized filename, or False depending on whether the file should be
traced or not.
"""
self.should_trace = should_trace
self.reset()
def reset(self):
# A dictionary with an entry for (Python source file name, line number
# in that file) if that line has been executed.
self.data = {}
# A cache of the decision about whether to trace execution in a file.
# A dict of filename to boolean.
self.should_trace_cache = {}
def _start_tracer(self):
tracer = Tracer()
tracer.data = self.data
tracer.should_trace = self.should_trace
tracer.should_trace_cache = self.should_trace_cache
tracer.start()
return tracer
# The trace function has to be set individually on each thread before
# execution begins. Ironically, the only support the threading module has
# for running code before the thread main is the tracing function. So we
# install this as a trace function, and the first time it's called, it does
# the real trace installation.
def _installation_trace(self, frame_unused, event_unused, arg_unused):
"""Called on new threads, installs the real tracer."""
# Remove ourselves as the trace function
sys.settrace(None)
# Install the real tracer
self._start_tracer()
# Return None to reiterate that we shouldn't be used for tracing.
return None
def start(self):
# Install the tracer on this thread.
self.tracer = self._start_tracer()
# Install our installation tracer in threading, to jump start other
# threads.
threading.settrace(self._installation_trace)
def stop(self):
self.tracer.stop()
threading.settrace(None)
def data_points(self):
"""Return the (filename, lineno) pairs collected."""
return self.data.keys()
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