--- a/cutils/util/__init__.py	Sun Dec 29 17:39:00 2024 +0100
+++ b/cutils/util/__init__.py	Sun Dec 29 18:22:22 2024 +0100
@@ -7,4 +7,144 @@
 
 """
 
-__all__ = []
+__all__ = ["normalize_filename",
+           "argv2algo",
+           "algotag2algotype",
+           "get_blake2b",
+           "get_blake2b_256",
+           "get_blake2s",
+           ]
+
+
+import argparse
+import hashlib
+
+
+def get_blake2b():
+    """Get the factory for blake2b"""
+    try:
+        return hashlib.blake2b
+    except AttributeError:
+        import pyblake2
+        return pyblake2.blake2b
+
+
+def get_blake2b_256():
+    """Get the factory for blake2b-256"""
+
+    try:
+        hashlib.blake2b
+    except AttributeError:
+        import pyblake2
+
+        def _get_blake():
+            return pyblake2.blake2b(digest_size=32)
+
+    else:
+
+        def _get_blake():
+            return hashlib.blake2b(digest_size=32)
+
+    return _get_blake
+
+
+def get_blake2s():
+    """Get the factory for blake2s"""
+    try:
+        return hashlib.blake2s
+    except AttributeError:
+        import pyblake2
+        return pyblake2.blake2s
+
+
+def argv2algo(s):
+    """Convert a command line algorithm specifier into a tuple with the
+    type/factory of the digest and the algorithms tag for output purposes.
+
+    :param str s: the specifier from the commane line
+    :return: the internal digest specification
+    :rtype: a tuple (digest_type_or_factory, name_in_output)
+    :raises argparse.ArgumentTypeError: for unrecognized algorithms or names
+
+    String comparisons are done case-insensitively.
+
+    """
+    s = s.lower()
+    if s in ("1", "sha1"):
+        return (hashlib.sha1, "SHA1")
+    elif s in ("224", "sha224"):
+        return (hashlib.sha224, "SHA224")
+    elif s in ("256", "sha256"):
+        return (hashlib.sha256, "SHA256")
+    elif s in ("384", "sha384"):
+        return (hashlib.sha384, "SHA384")
+    elif s in ("512", "sha512"):
+        return (hashlib.sha512, "SHA512")
+    elif s in ("3-224", "sha3-224"):
+        return (hashlib.sha3_224, "SHA3-224")
+    elif s in ("3-256", "sha3-256"):
+        return (hashlib.sha3_256, "SHA3-256")
+    elif s in ("3-384", "sha3-384"):
+        return (hashlib.sha3_384, "SHA3-384")
+    elif s in ("3-512", "sha3-512"):
+        return (hashlib.sha3_512, "SHA3-512")
+    elif s in ("blake2b", "blake2b-512", "blake2", "blake2-512"):
+        return (get_blake2b(), "BLAKE2b")
+    elif s in ("blake2s", "blake2s-256"):
+        return (get_blake2s(), "BLAKE2s")
+    elif s in ("blake2-256", "blake2b-256"):
+        return (get_blake2b_256(), "BLAKE2b-256")
+    elif s == "md5":
+        return (hashlib.md5, "MD5")
+    else:
+        raise argparse.ArgumentTypeError(
+            "`{}' is not a recognized algorithm".format(s))
+
+
+def algotag2algotype(s):
+    """Convert the algorithm specifier in a BSD-style digest file to the
+    type/factory of the corresponding algorithm.
+
+    :param str s: the tag (i.e. normalized name) or the algorithm
+    :return: the digest type or factory for `s`
+    :raises ValueError: on unknown and/or unhandled algorithms
+
+    All string comparisons are case-sensitive.
+
+    """
+    if s == "SHA1":
+        return hashlib.sha1
+    elif s == "SHA224":
+        return hashlib.sha224
+    elif s == "SHA256":
+        return hashlib.sha256
+    elif s == "SHA384":
+        return hashlib.sha384
+    elif s == "SHA512":
+        return hashlib.sha512
+    elif s == "SHA3-224":
+        return hashlib.sha3_224
+    elif s == "SHA3-256":
+        return hashlib.sha3_256
+    elif s == "SHA3-384":
+        return hashlib.sha3_384
+    elif s == "SHA3-512":
+        return hashlib.sha3_512
+    elif s in ("BLAKE2b", "BLAKE2b-512", "BLAKE2b512"):  # compat for openssl
+        return get_blake2b()
+    elif s in ("BLAKE2s", "BLAKE2s-256", "BLAKE2s256"):  # compat for openssl
+        return get_blake2s()
+    elif s in ("BLAKE2b-256", "BLAKE2b256"):   # also compat for openssl dgst
+        return get_blake2b_256()
+    elif s == "MD5":
+        return hashlib.md5
+    else:
+        raise ValueError("unknown algorithm: {}".format(s))
+
+
+def normalize_filename(filename, strip_leading_dot_slash=False):
+    filename = filename.replace("\\", "/")
+    if strip_leading_dot_slash:
+        while filename.startswith("./"):
+            filename = filename[2:]
+    return filename