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Public backends are those printed by "--list-backends" and thus considered valid by the configure script. Signed-off-by: Lluís Vilanova <vilanova@ac.upc.edu> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
130 lines
3.8 KiB
Python
130 lines
3.8 KiB
Python
#!/usr/bin/env python
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# -*- coding: utf-8 -*-
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"""
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Backend management.
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Creating new backends
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---------------------
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A new backend named 'foo-bar' corresponds to Python module
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'tracetool/backend/foo_bar.py'.
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A backend module should provide a docstring, whose first non-empty line will be
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considered its short description.
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All backends must generate their contents through the 'tracetool.out' routine.
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Backend attributes
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------------------
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========= ====================================================================
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Attribute Description
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========= ====================================================================
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PUBLIC If exists and is set to 'True', the backend is considered "public".
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========= ====================================================================
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Backend functions
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-----------------
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======== =======================================================================
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Function Description
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======== =======================================================================
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<format> Called to generate the format- and backend-specific code for each of
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the specified events. If the function does not exist, the backend is
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considered not compatible with the given format.
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======== =======================================================================
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"""
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__author__ = "Lluís Vilanova <vilanova@ac.upc.edu>"
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__copyright__ = "Copyright 2012, Lluís Vilanova <vilanova@ac.upc.edu>"
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__license__ = "GPL version 2 or (at your option) any later version"
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__maintainer__ = "Stefan Hajnoczi"
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__email__ = "stefanha@linux.vnet.ibm.com"
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import os
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import tracetool
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def get_list(only_public = False):
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"""Get a list of (name, description) pairs."""
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res = [("nop", "Tracing disabled.")]
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modnames = []
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for filename in os.listdir(tracetool.backend.__path__[0]):
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if filename.endswith('.py') and filename != '__init__.py':
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modnames.append(filename.rsplit('.', 1)[0])
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for modname in modnames:
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module = tracetool.try_import("tracetool.backend." + modname)
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# just in case; should never fail unless non-module files are put there
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if not module[0]:
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continue
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module = module[1]
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public = getattr(module, "PUBLIC", False)
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if only_public and not public:
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continue
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doc = module.__doc__
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if doc is None:
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doc = ""
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doc = doc.strip().split("\n")[0]
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name = modname.replace("_", "-")
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res.append((name, doc))
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return res
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def exists(name):
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"""Return whether the given backend exists."""
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if len(name) == 0:
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return False
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if name == "nop":
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return True
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name = name.replace("-", "_")
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return tracetool.try_import("tracetool.backend." + name)[1]
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def compatible(backend, format):
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"""Whether a backend is compatible with the given format."""
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if not exists(backend):
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raise ValueError("unknown backend: %s" % backend)
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backend = backend.replace("-", "_")
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format = format.replace("-", "_")
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if backend == "nop":
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return True
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else:
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func = tracetool.try_import("tracetool.backend." + backend,
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format, None)[1]
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return func is not None
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def _empty(events):
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pass
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def generate(backend, format, events):
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"""Generate the per-event output for the given (backend, format) pair."""
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if not compatible(backend, format):
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raise ValueError("backend '%s' not compatible with format '%s'" %
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(backend, format))
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backend = backend.replace("-", "_")
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format = format.replace("-", "_")
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if backend == "nop":
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func = tracetool.try_import("tracetool.format." + format,
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"nop", _empty)[1]
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else:
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func = tracetool.try_import("tracetool.backend." + backend,
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format, None)[1]
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func(events)
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