I'm currently working on #1149. In Matroska, some elements have a UID which is implemented as a 64 bit unsigned integer. ByteVector currently does not have conversions for ULongLong, only LongLong. Casting an unsigned integer type to a signed integer type is implementation-defined if the value is higher than the max value of the signed type, so I would like to have a ULongLong function available to avoid the cast.

While looking at the code, I made some other improvements as well. Here is a summary of the changes:

• Added ByteVector::toULongLong, ByteVector::fromULongLong, and tests for both
• Added ByteVector::fromUShort, and tests
• Added tests for all existing integer-based ByteVector::from* functions. Currently, there are no tests for these functions
• Fixed a function reference in the documentation for ByteVector::toLongLong (I presume this was a copy/paste error)