Preparation to make decoder use less memory and API more type safe.
Now each scalar type has it's own struct type so it can store different
things and enables to have a scalar interface.
Also own types will enable experimenting with decode DLS designs like
using chained methods that are type aware.
Rework time helpers to use new functions
Fix panic in tar decoder where sym value might be missing
Still not very happy about the API but it's getting better.
Later mappers should be able to rely on sym being a value of a certain type.
In this crash case tar.go had this:
d.FieldUTF8NullFixedLen("mtime", 12, scalar.SymUParseUint(8), scalar.DescriptionSymUUnixTime)
If mtime was empty string SymUParseUint was not even called so did not bail out running
all mappers.
PSSH decoding probably got broken in some refactoring. system id is 16 bytes,
also scalar mapper should use cloned reader to not affect reader which in the case
broke reading system id bytes.
Add test with playread and widevine pssh boxes
Related to #282
Rename s/interface{}/any/g
Preparation for using generics in decode API and native jq funcations etc
Remove some unused linter ignores as linter has been fixed
Remove bitio.Buffer layer. bitio.Buffer was a kitchen sink layer with helpers
now it's just a buffer and most functions have been moved to decode instead.
bitio package now only have primitive types and functions simialar to standard
library io and bytes packages.
Make nearly eveything internally use bitio.Bit* interfaces so that slicing work
correctly this will also make it possible to start experimenting with more
complicated silcing helpers, ex things like:
breplace(.header.bitrate; 123) to get a new buffer with bitrate changed.
Move scalar into own package.
Split scalar code into decode related scalar code (that reads etc) and
scalar code that just transform the scalar value.
Use a scalar.Mapper interface instead of just a function.
Make mappers, assert and validat impement the interface.
