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diff --git a/scripts/maint/practracker/practracker.py b/scripts/maint/practracker/practracker.py
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+++ b/scripts/maint/practracker/practracker.py
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+#!/usr/bin/python
+
+"""
+Best-practices tracker for Tor source code.
+
+Go through the various .c files and collect metrics about them. If the metrics
+violate some of our best practices and they are not found in the optional
+exceptions file, then log a problem about them.
+
+We currently do metrics about file size, function size and number of includes.
+
+practracker.py should be run with its second argument pointing to the Tor
+top-level source directory like this:
+  $ python3 ./scripts/maint/practracker/practracker.py .
+
+To regenerate the exceptions file so that it allows all current
+problems in the Tor source, use the --regen flag:
+  $ python3 --regen ./scripts/maint/practracker/practracker.py .
+"""
+
+from __future__ import print_function
+
+import os, sys
+
+import metrics
+import util
+import problem
+
+# The filename of the exceptions file (it should be placed in the practracker directory)
+EXCEPTIONS_FNAME = "./exceptions.txt"
+
+# Recommended file size
+MAX_FILE_SIZE = 3000 # lines
+# Recommended function size
+MAX_FUNCTION_SIZE = 100 # lines
+# Recommended number of #includes
+MAX_INCLUDE_COUNT = 50
+
+#######################################################
+
+# ProblemVault singleton
+ProblemVault = None
+
+# The Tor source code topdir
+TOR_TOPDIR = None
+
+#######################################################
+
+if sys.version_info[0] <= 2:
+    def open_file(fname):
+        return open(fname, 'r')
+else:
+    def open_file(fname):
+        return open(fname, 'r', encoding='utf-8')
+
+def consider_file_size(fname, f):
+    """Consider file size issues for 'f' and return True if a new issue was found"""
+    file_size = metrics.get_file_len(f)
+    if file_size > MAX_FILE_SIZE:
+        p = problem.FileSizeProblem(fname, file_size)
+        return ProblemVault.register_problem(p)
+    return False
+
+def consider_includes(fname, f):
+    """Consider #include issues for 'f' and return True if a new issue was found"""
+    include_count = metrics.get_include_count(f)
+
+    if include_count > MAX_INCLUDE_COUNT:
+        p = problem.IncludeCountProblem(fname, include_count)
+        return ProblemVault.register_problem(p)
+    return False
+
+def consider_function_size(fname, f):
+    """Consider the function sizes for 'f' and return True if a new issue was found"""
+    found_new_issues = False
+
+    for name, lines in metrics.get_function_lines(f):
+        # Don't worry about functions within our limits
+        if lines <= MAX_FUNCTION_SIZE:
+            continue
+
+        # That's a big function! Issue a problem!
+        canonical_function_name = "%s:%s()" % (fname, name)
+        p = problem.FunctionSizeProblem(canonical_function_name, lines)
+        found_new_issues |= ProblemVault.register_problem(p)
+
+    return found_new_issues
+
+#######################################################
+
+def consider_all_metrics(files_list):
+    """Consider metrics for all files, and return True if new issues were found"""
+    found_new_issues = False
+    for fname in files_list:
+        with open_file(fname) as f:
+            found_new_issues |= consider_metrics_for_file(fname, f)
+    return found_new_issues
+
+def consider_metrics_for_file(fname, f):
+    """
+    Consider the various metrics for file with filename 'fname' and file descriptor 'f'.
+    Return True if we found new issues.
+    """
+    # Strip the useless part of the path
+    if fname.startswith(TOR_TOPDIR):
+        fname = fname[len(TOR_TOPDIR):]
+
+    found_new_issues = False
+
+    # Get file length
+    found_new_issues |= consider_file_size(fname, f)
+
+    # Consider number of #includes
+    f.seek(0)
+    found_new_issues |= consider_includes(fname, f)
+
+    # Get function length
+    f.seek(0)
+    found_new_issues |= consider_function_size(fname, f)
+
+    return found_new_issues
+
+HEADER="""\
+# Welcome to the exceptions file for Tor's best-practices tracker!
+#
+# Each line of this file represents a single violation of Tor's best
+# practices -- typically, a violation that we had before practracker.py
+# first existed.
+#
+# There are three kinds of problems that we recognize right now:
+#   function-size -- a function of more than {MAX_FUNCTION_SIZE} lines.
+#   file-size -- a file of more than {MAX_FILE_SIZE} lines.
+#   include-count -- a file with more than {MAX_INCLUDE_COUNT} #includes.
+#
+# Each line below represents a single exception that practracker should
+# _ignore_. Each line has four parts:
+#  1. The word "problem".
+#  2. The kind of problem.
+#  3. The location of the problem: either a filename, or a
+#     filename:functionname pair.
+#  4. The magnitude of the problem to ignore.
+#
+# So for example, consider this line:
+#    problem file-size /src/core/or/connection_or.c 3200
+#
+# It tells practracker to allow the mentioned file to be up to 3200 lines
+# long, even though ordinarily it would warn about any file with more than
+# {MAX_FILE_SIZE} lines.
+#
+# You can either edit this file by hand, or regenerate it completely by
+# running `make practracker-regen`.
+#
+# Remember: It is better to fix the problem than to add a new exception!
+
+""".format(**globals())
+
+def main(argv):
+    import argparse
+
+    progname = argv[0]
+    parser = argparse.ArgumentParser(prog=progname)
+    parser.add_argument("--regen", action="store_true",
+                        help="Regenerate the exceptions file")
+    parser.add_argument("--exceptions",
+                        help="Override the location for the exceptions file")
+    parser.add_argument("topdir", default=".", nargs="?",
+                        help="Top-level directory for the tor source")
+    args = parser.parse_args(argv[1:])
+
+    global TOR_TOPDIR
+    TOR_TOPDIR = args.topdir
+    if args.exceptions:
+        exceptions_file = args.exceptions
+    else:
+        exceptions_file = os.path.join(TOR_TOPDIR, "scripts/maint/practracker", EXCEPTIONS_FNAME)
+
+    # 1) Get all the .c files we care about
+    files_list = util.get_tor_c_files(TOR_TOPDIR)
+
+    # 2) Initialize problem vault and load an optional exceptions file so that
+    # we don't warn about the past
+    global ProblemVault
+
+    if args.regen:
+        tmpname = exceptions_file + ".tmp"
+        tmpfile = open(tmpname, "w")
+        sys.stdout = tmpfile
+        sys.stdout.write(HEADER)
+        ProblemVault = problem.ProblemVault()
+    else:
+        ProblemVault = problem.ProblemVault(exceptions_file)
+
+    # 3) Go through all the files and report problems if they are not exceptions
+    found_new_issues = consider_all_metrics(files_list)
+
+    if args.regen:
+        tmpfile.close()
+        os.rename(tmpname, exceptions_file)
+        sys.exit(0)
+
+    # If new issues were found, try to give out some advice to the developer on how to resolve it.
+    if found_new_issues and not args.regen:
+        new_issues_str = """\
+FAILURE: practracker found new problems in the code: see warnings above.
+
+Please fix the problems if you can, and update the exceptions file
+({}) if you can't.
+
+See doc/HACKING/HelpfulTools.md for more information on using practracker.\
+""".format(exceptions_file)
+        print(new_issues_str)
+
+    sys.exit(found_new_issues)
+
+if __name__ == '__main__':
+    main(sys.argv)