Add Shorten (SHN) support (#1257)

* Add Shorten (SHN) support

* Add `<cmath>` include and use `std::log2`

* Use `uintptr_t` for buffer size calculations

* Work around `byteSwap` not using fixed width types

* Remove four-character codes

* Attempt to fix `static_assert`

* Revert previous commit

* Update `read_uint`* functions

* Use ByteVector for byte swaps

* Use different ByteVector ctor

* Rework variable-length input to use ByteVector

* Rename some variables

* Naming and formatting cleanup

* Add basic Shorten tests

* Rename a constant

* Rename `internalFileType` to `fileType`

* Add documentation on `fileType` meaning

* Add DO_NOT_DOCUMENT guard

* Fix shadowVariable issues reported by cppcheck

cppcheck --enable=all --inline-suppr \
  --suppress=noExplicitConstructor --suppress=unusedFunction \
  --suppress=missingIncludeSystem --project=compile_commands.json

* Formatting cleanup

* More explicit types

Reason for these changes: getRiceGolombCode(k, uInt32CodeSize) was
called with int k for uint32_t& argument.
There was also a warning from MSVC for line 299:
warning C4267: 'argument': conversion from 'size_t' to 'int'

* Additional explicit types

* Rename `SHN` namespace to `Shorten`

Also rename files to match

---------

Co-authored-by: Urs Fleisch <ufleisch@users.sourceforge.net>

taglib/fileref.cpp

@@ -57,6 +57,7 @@
 #include "xmfile.h"
 #include "dsffile.h"
 #include "dsdifffile.h"
+#include "shortenfile.h"
 
 using namespace TagLib;
 
@@ -180,6 +181,8 @@ namespace
       file = new DSF::File(stream, readAudioProperties, audioPropertiesStyle);
     else if(ext == "DFF" || ext == "DSDIFF")
       file = new DSDIFF::File(stream, readAudioProperties, audioPropertiesStyle);
+    else if(ext == "SHN")
+      file = new Shorten::File(stream, readAudioProperties, audioPropertiesStyle);
 
     // if file is not valid, leave it to content-based detection.
 
@@ -231,6 +234,8 @@ namespace
       file = new DSF::File(stream, readAudioProperties, audioPropertiesStyle);
     else if(DSDIFF::File::isSupported(stream))
       file = new DSDIFF::File(stream, readAudioProperties, audioPropertiesStyle);
+    else if(Shorten::File::isSupported(stream))
+      file = new Shorten::File(stream, readAudioProperties, audioPropertiesStyle);
 
     // isSupported() only does a quick check, so double check the file here.
 
@@ -436,6 +441,7 @@ StringList FileRef::defaultFileExtensions()
   l.append("dsf");
   l.append("dff");
   l.append("dsdiff"); // alias for "dff"
+  l.append("shn");
 
   return l;
 }