Merge remote-tracking branch 'remotes/stefanha/tags/tracing-pull-request' into staging

Tracing pull request

# gpg: Signature made Wed 07 May 2014 18:14:02 BST using RSA key ID 81AB73C8
# gpg: Good signature from "Stefan Hajnoczi <stefanha@redhat.com>"
# gpg:                 aka "Stefan Hajnoczi <stefanha@gmail.com>"

* remotes/stefanha/tags/tracing-pull-request:
  configure: Show trace output file conditionally
  trace: [tracetool] Minimize the amount of per-backend code
  trace: [simple] Bump up log version number
  trace: [tracetool] Change format docs to point to the generated file
  trace: [tracetool] Show list of frontends and backends sorted by name
  trace: [tracetool] Cosmetic changes
  trace: [tracetool] Spacing changes
  trace: [tracetool] Add methods 'Event.copy' and 'Arguments.copy'
  trace: [tracetool] Add method 'Event.api' to build event names

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 33 insertions, 41 deletions

diff --git a/scripts/tracetool/backend/__init__.py b/scripts/tracetool/backend/__init__.py
index f0314ee376..5e36f0415d 100644
--- a/scripts/tracetool/backend/__init__.py
+++ b/scripts/tracetool/backend/__init__.py
@@ -30,17 +30,24 @@ PUBLIC    If exists and is set to 'True', the backend is considered "public".
 Backend functions
 -----------------
 
-======== =======================================================================
-Function Description
-======== =======================================================================
-<format> Called to generate the format- and backend-specific code for each of
-         the specified events. If the function does not exist, the backend is
-         considered not compatible with the given format.
-======== =======================================================================
+All the following functions are optional, and no output will be generated if
+they do not exist.
+
+=============================== ==============================================
+Function                        Description
+=============================== ==============================================
+generate_<format>_begin(events) Generate backend- and format-specific file
+                                header contents.
+generate_<format>_end(events)   Generate backend- and format-specific file
+                                footer contents.
+generate_<format>(event)        Generate backend- and format-specific contents
+                                for the given event.
+=============================== ==============================================
+
 """
 
 __author__     = "Lluís Vilanova <vilanova@ac.upc.edu>"
-__copyright__  = "Copyright 2012, Lluís Vilanova <vilanova@ac.upc.edu>"
+__copyright__  = "Copyright 2012-2014, Lluís Vilanova <vilanova@ac.upc.edu>"
 __license__    = "GPL version 2 or (at your option) any later version"
 
 __maintainer__ = "Stefan Hajnoczi"
@@ -59,7 +66,7 @@ def get_list(only_public = False):
     for filename in os.listdir(tracetool.backend.__path__[0]):
         if filename.endswith('.py') and filename != '__init__.py':
             modnames.append(filename.rsplit('.', 1)[0])
-    for modname in modnames:
+    for modname in sorted(modnames):
         module = tracetool.try_import("tracetool.backend." + modname)
 
         # just in case; should never fail unless non-module files are put there
@@ -91,39 +98,24 @@ def exists(name):
     return tracetool.try_import("tracetool.backend." + name)[1]
 
 
-def compatible(backend, format):
-    """Whether a backend is compatible with the given format."""
-    if not exists(backend):
-        raise ValueError("unknown backend: %s" % backend)
-
-    backend = backend.replace("-", "_")
-    format = format.replace("-", "_")
-
-    if backend == "nop":
-        return True
-    else:
-        func = tracetool.try_import("tracetool.backend." + backend,
-                                    format, None)[1]
-        return func is not None
-
-
-def _empty(events):
-    pass
+class Wrapper:
+    def __init__(self, backend, format):
+        self._backend = backend.replace("-", "_")
+        self._format = format.replace("-", "_")
+        assert exists(self._backend)
+        assert tracetool.format.exists(self._format)
 
-def generate(backend, format, events):
-    """Generate the per-event output for the given (backend, format) pair."""
-    if not compatible(backend, format):
-        raise ValueError("backend '%s' not compatible with format '%s'" %
-                         (backend, format))
+    def _run_function(self, name, *args, **kwargs):
+        func = tracetool.try_import("tracetool.backend." + self._backend,
+                                    name % self._format, None)[1]
+        if func is not None:
+            func(*args, **kwargs)
 
-    backend = backend.replace("-", "_")
-    format = format.replace("-", "_")
+    def generate_begin(self, events):
+        self._run_function("generate_%s_begin", events)
 
-    if backend == "nop":
-        func = tracetool.try_import("tracetool.format." + format,
-                                    "nop", _empty)[1]
-    else:
-        func = tracetool.try_import("tracetool.backend." + backend,
-                                    format, None)[1]
+    def generate(self, event):
+        self._run_function("generate_%s", event)
 
-    func(events)
+    def generate_end(self, events):
+        self._run_function("generate_%s_end", events)