Rewrite audio.py to jive with image.py (#91886)

Similar to the rewrite of email/mime/image.py and associated test after the
deprecation of imghdr.py, thisrewrites email/mime/audio.py and associated
tests after the deprecation of sndhdr.py.

Closes #91885

1 files changed, 55 insertions, 53 deletions

diff --git a/Lib/email/mime/audio.py b/Lib/email/mime/audio.py
index e859c2e..8815f5c 100644
--- a/Lib/email/mime/audio.py
+++ b/Lib/email/mime/audio.py
@@ -11,58 +11,6 @@ from email import encoders
 from email.mime.nonmultipart import MIMENonMultipart
 
 
-_tests = []
-
-def _test_aifc_aiff(h, f):
-    if not h.startswith(b'FORM'):
-        return None
-    if h[8:12] in {b'AIFC', b'AIFF'}:
-        return 'x-aiff'
-    else:
-        return None
-
-_tests.append(_test_aifc_aiff)
-
-
-def _test_au(h, f):
-    if h.startswith(b'.snd'):
-        return 'basic'
-    else:
-        return None
-
-_tests.append(_test_au)
-
-
-def _test_wav(h, f):
-    import wave
-    # 'RIFF' <len> 'WAVE' 'fmt ' <len>
-    if not h.startswith(b'RIFF') or h[8:12] != b'WAVE' or h[12:16] != b'fmt ':
-        return None
-    else:
-        return "x-wav"
-
-_tests.append(_test_wav)
-
-
-# There are others in sndhdr that don't have MIME types. :(
-# Additional ones to be added to sndhdr? midi, mp3, realaudio, wma??
-def _whatsnd(data):
-    """Try to identify a sound file type.
-
-    sndhdr.what() has a pretty cruddy interface, unfortunately.  This is why
-    we re-do it here.  It would be easier to reverse engineer the Unix 'file'
-    command and use the standard 'magic' file, as shipped with a modern Unix.
-    """
-    hdr = data[:512]
-    fakefile = BytesIO(hdr)
-    for testfn in _tests:
-        res = testfn(hdr, fakefile)
-        if res is not None:
-            return res
-    else:
-        return None
-
-
 class MIMEAudio(MIMENonMultipart):
     """Class for generating audio/* MIME documents."""
 
@@ -89,10 +37,64 @@ class MIMEAudio(MIMENonMultipart):
         header.
         """
         if _subtype is None:
-            _subtype = _whatsnd(_audiodata)
+            _subtype = _what(_audiodata)
         if _subtype is None:
             raise TypeError('Could not find audio MIME subtype')
         MIMENonMultipart.__init__(self, 'audio', _subtype, policy=policy,
                                   **_params)
         self.set_payload(_audiodata)
         _encoder(self)
+
+
+_rules = []
+
+
+# Originally from the sndhdr module.
+#
+# There are others in sndhdr that don't have MIME types. :(
+# Additional ones to be added to sndhdr? midi, mp3, realaudio, wma??
+def _what(data):
+    # Try to identify a sound file type.
+    #
+    # sndhdr.what() had a pretty cruddy interface, unfortunately.  This is why
+    # we re-do it here.  It would be easier to reverse engineer the Unix 'file'
+    # command and use the standard 'magic' file, as shipped with a modern Unix.
+    hdr = data[:512]
+    fakefile = BytesIO(hdr)
+    for testfn in _rules:
+        if res := testfn(hdr, fakefile):
+            return res
+    else:
+        return None
+
+
+def rule(rulefunc):
+    _rules.append(rulefunc)
+    return rulefunc
+
+
+@rule
+def _aiff(h, f):
+    if not h.startswith(b'FORM'):
+        return None
+    if h[8:12] in {b'AIFC', b'AIFF'}:
+        return 'x-aiff'
+    else:
+        return None
+
+
+@rule
+def _au(h, f):
+    if h.startswith(b'.snd'):
+        return 'basic'
+    else:
+        return None
+
+
+@rule
+def _wav(h, f):
+    # 'RIFF' <len> 'WAVE' 'fmt ' <len>
+    if not h.startswith(b'RIFF') or h[8:12] != b'WAVE' or h[12:16] != b'fmt ':
+        return None
+    else:
+        return "x-wav"