stdlib: Update the stdlib resource's md5 utils

The commit does the following:

- Moves the md5 functions to their own Python module (this will allow us
to use this elsewhere).
- Add functionality to enable md5 values for directories.
- Adds Pyunit tests for the md5 functionality.

Change-Id: I224d4584ed6c35fac3a75e221b3cb48d863ffa6f
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/58849
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Bobby Bruce <bbruce@ucdavis.edu>
Maintainer: Bobby Bruce <bbruce@ucdavis.edu>

tests/pyunit/stdlib/resources/pyunit_md5_utils_check.py

@@ -0,0 +1,116 @@
+# Copyright (c) 2022 The Regents of the University of California
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met: redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer;
+# redistributions in binary form must reproduce the above copyright
+# notice, this list of conditions and the following disclaimer in the
+# documentation and/or other materials provided with the distribution;
+# neither the name of the copyright holders nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+import unittest
+import tempfile
+import os
+import shutil
+from pathlib import Path
+
+from gem5.resources.md5_utils import md5_file, md5_dir
+
+
+class MD5FileTestSuite(unittest.TestCase):
+    """Test cases for gem5.resources.md5_utils.md5_file()"""
+
+    def test_md5FileConsistency(self) -> None:
+        # This test ensures the md5 algorithm we use does not change the md5
+        # value over time.
+
+        file = tempfile.NamedTemporaryFile(mode="w", delete=False)
+        file.write("This is a test string, to be put in a temp file")
+        file.close()
+        md5 = md5_file(Path(file.name))
+        os.remove(file.name)
+
+        self.assertEquals("b113b29fce251f2023066c3fda2ec9dd", md5)
+
+    def test_identicalFilesIdenticalMd5(self) -> None:
+        # This test ensures that two files with exactly the same contents have
+        # the same md5 value.
+
+        test_str = "This is a test"
+
+        file = tempfile.NamedTemporaryFile(mode="w", delete=False)
+        file.write(test_str)
+        file.close()
+        first_file_md5 = md5_file(Path(file.name))
+
+        os.remove(file.name)
+
+        file = tempfile.NamedTemporaryFile(mode="w", delete=False)
+        file.write(test_str)
+        file.close()
+        second_file_md5 = md5_file(Path(file.name))
+
+        os.remove(file.name)
+
+        self.assertEquals(first_file_md5, second_file_md5)
+
+
+class MD5DirTestSuite(unittest.TestCase):
+    """Test cases for gem5.resources.md5_utils.md5_dir()"""
+
+    def _create_temp_directory(self) -> Path:
+
+        dir = tempfile.mkdtemp()
+
+        with open(os.path.join(dir, "file1"), "w") as f:
+            f.write("Some test data here")
+
+        with open(os.path.join(dir, "file2"), "w") as f:
+            f.write("Some more test data")
+
+        os.mkdir(os.path.join(dir, "dir2"))
+
+        with open(os.path.join(dir, "dir2", "file1"), "w") as f:
+            f.write("Yet more data")
+
+        return Path(dir)
+
+    def test_md5DirConsistency(self) -> None:
+        # This test ensures the md5 algorithm we use does not change the value
+        # given for directories over time.
+
+        dir = self._create_temp_directory()
+        md5 = md5_dir(dir)
+        shutil.rmtree(dir)
+
+        self.assertEquals("ad5ac785de44c9fc2fe2798cab2d7b1a", md5)
+
+    def test_identicalDirsIdenticalMd5(self) -> None:
+        # This test ensures that two directories with exactly the same contents
+        # have the same md5 value.
+
+        dir1 = self._create_temp_directory()
+        first_md5 = md5_dir(dir1)
+        shutil.rmtree(dir1)
+
+        dir2 = self._create_temp_directory()
+        second_md5 = md5_dir(dir2)
+        shutil.rmtree(dir2)
+
+        self.assertEquals(first_md5, second_md5)