Previously, ChunkID's from_big_endian_number() and
as_big_endian_number() weren't inverses of each other.
ChunkID::from_big_endian_number() used to take an u32 that contained
`('f' << 24) | ('t' << 16) | ('y' << 8) | 'p'`, that is
'f', 't', 'y', 'p' in memory on big-endian and 'p', 'y', 't', 'f'
on little-endian, and return a ChunkID for 'f', 't', 'y', 'p'.
ChunkID::as_big_endian_number() used to return an u32 that for a
ChunkID storing 'f', 't', 'y', 'p' was always 'f', 't', 'y', 'p'
in memory on both little-endian and big-endian, that is it stored
`('f' << 24) | ('t' << 16) | ('y' << 8) | 'p'` on big-endian and
`('p' << 24) | ('y' << 16) | ('t' << 8) | 'f'` on little-endian.
`ChunkID::from_big_endian_number(0x11223344).as_big_endian_number()`
returned 0x44332211.
This change makes the two methods self-consistent: they now take
and return a u32 that always has the first ChunkID part in the
highest bits of the u32 (`'f' << 24`), and so on. That also means
they return a u32 that in-memory looks differently on big-endian
and little-endian. Since that's normal for numbers, this also
renames the two methods to just `from_number()` and `to_number()`.
With the semantics cleared up, change the one use in ISOBMFF to read a
BigEndian for chunk headers and brand codes. This has the effect of
tags now being printed in the right order.
Before:
```sh
% Build/lagom/bin/isobmff ~/Downloads/sample1.jp2
Unknown Box (' Pj')
[ 4 bytes ]
('pytf') (version = 0, flags = 0x0)
- major_brand = ' 2pj'
- minor_version = 0
- compatible_brands = { ' 2pj' }
Unknown Box ('h2pj')
[ 37 bytes ]
Unknown Box ('fniu')
[ 92 bytes ]
Unknown Box (' lmx')
[ 2736 bytes ]
Unknown Box ('c2pj')
[ 667336 bytes ]
```
After:
```sh
% Build/lagom/bin/isobmff ~/Downloads/sample1.jp2
hmm 0x11223344 0x11223344
Unknown Box ('jP ')
[ 4 bytes ]
('ftyp' ) (version = 0, flags = 0x0)
- major_brand = 'jp2 '
- minor_version = 0
- compatible_brands = { 'jp2 ' }
Unknown Box ('jp2h')
[ 37 bytes ]
Unknown Box ('uinf')
[ 92 bytes ]
Unknown Box ('xml ')
[ 2736 bytes ]
Unknown Box ('jp2c')
[ 667336 bytes ]
```
There's now two namespaces, RIFF (little-endian) and IFF (big-endian)
which (for the most part) contain the same kinds of structures for
handling similar data in both formats. (They also share almost all of
their implementation) The main types are ChunkHeader and (Owned)Chunk.
While Chunk has no ownership over the data it accesses (and can only be
constructed from a byte view), OwnedChunk has ownership over this data
and is aimed at reading from streams.
OwnedList, implementing the standard RIFF LIST type, is currently only
implemented for RIFF due to its only user being WAV, but it may be
generalized in the future for use by IFF.
Co-authored-by: Timothy Flynn <trflynn89@pm.me>
This splits the RIFFTypes header/TU into the WAV specific parts, which
move to WavTypes.h, as well as the general RIFF parts which move to the
new LibRIFF.
Sidenote for the spec comments: even though they are linked from a site
that explains the WAV format, the document is the (an) overall RIFF spec
from Microsoft. A better source may be used later; the changes to the
header are as minimal as possible.
