tracetool: Rewrite infrastructure as python modules

The tracetool script is written in shell and has hit several portability
problems due to shell quirks or external tools across host platforms.
Additionally the amount of string processing and lack of real data
structures makes it tough to implement code generator backends for
tracers that are more complex.

This patch replaces the shell version of tracetool with a Python
version.  The new tracetool design is:

  scripts/tracetool.py - top-level script
  scripts/tracetool/backend/ - tracer backends live here (simple, ust)
  scripts/tracetool/format/  - output formats live here (.c, .h)

There is common code for trace-events definition parsing so that
backends can focus on generating code rather than parsing input.

Support for all existing backends (nop, stderr, simple, ust,
and dtrace) is added back in follow-up patches.

[Commit description written by Stefan Hajnoczi]

Signed-off-by: Lluís Vilanova <vilanova@ac.upc.edu>
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>

1 files changed, 99 insertions, 0 deletions

diff --git a/scripts/tracetool/format/__init__.py b/scripts/tracetool/format/__init__.py
new file mode 100644
index 0000000000..0e4baf0e56
--- /dev/null
+++ b/scripts/tracetool/format/__init__.py
@@ -0,0 +1,99 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+"""
+Format management.
+
+
+Creating new formats
+--------------------
+
+A new format named 'foo-bar' corresponds to Python module
+'tracetool/format/foo_bar.py'.
+
+A format module should provide a docstring, whose first non-empty line will be
+considered its short description.
+
+All formats must generate their contents through the 'tracetool.out' routine.
+
+
+Format functions
+----------------
+
+All the following functions are optional, and no output will be generated if
+they do not exist.
+
+======== =======================================================================
+Function Description
+======== =======================================================================
+begin    Called to generate the format-specific file header.
+end      Called to generate the format-specific file footer.
+nop      Called to generate the per-event contents when the event is disabled or
+         the selected backend is 'nop'.
+======== =======================================================================
+"""
+
+__author__     = "Lluís Vilanova <vilanova@ac.upc.edu>"
+__copyright__  = "Copyright 2012, Lluís Vilanova <vilanova@ac.upc.edu>"
+__license__    = "GPL version 2 or (at your option) any later version"
+
+__maintainer__ = "Stefan Hajnoczi"
+__email__      = "stefanha@linux.vnet.ibm.com"
+
+
+import pkgutil
+
+import tracetool
+
+
+def get_list():
+    """Get a list of (name, description) pairs."""
+    res = []
+    for _, modname, _ in pkgutil.iter_modules(tracetool.format.__path__):
+        module = tracetool.try_import("tracetool.format." + modname)
+
+        # just in case; should never fail unless non-module files are put there
+        if not module[0]:
+            continue
+        module = module[1]
+
+        doc = module.__doc__
+        if doc is None:
+            doc = ""
+        doc = doc.strip().split("\n")[0]
+
+        name = modname.replace("_", "-")
+        res.append((name, doc))
+    return res
+
+
+def exists(name):
+    """Return whether the given format exists."""
+    if len(name) == 0:
+        return False
+    name = name.replace("-", "_")
+    return tracetool.try_import("tracetool.format." + name)[1]
+
+
+def _empty(events):
+    pass
+
+def generate_begin(name, events):
+    """Generate the header of the format-specific file."""
+    if not exists(name):
+        raise ValueError("unknown format: %s" % name)
+
+    name = name.replace("-", "_")
+    func = tracetool.try_import("tracetool.format." + name,
+                                "begin", _empty)[1]
+    func(events)
+
+def generate_end(name, events):
+    """Generate the footer of the format-specific file."""
+    if not exists(name):
+        raise ValueError("unknown format: %s" % name)
+
+    name = name.replace("-", "_")
+    func = tracetool.try_import("tracetool.format." + name,
+                                "end", _empty)[1]
+    func(events)