* change miscellaneous things to more idiomatic zig style
* change the digest length to 24 bytes instead of 48. This is
still 70 more bits than UUIDs. For an analysis of probability of
collisions, see:
https://en.wikipedia.org/wiki/Universally_unique_identifier#Collisions
* fix the API having the possibility of mismatched allocators
* fix some error paths to behave properly
* modify the guarantees about when file contents are loaded for input files
* pwrite instead of seek + write
* implement isProblematicTimestamp
* fix tests with regards to a working isProblematicTimestamp function.
this requires sleeping until the current timestamp becomes
unproblematic.
* introduce std.fs.File.INode, a cross platform type abstraction
so that cache hash implementation does not need to reach into std.os.
People using the API as intended would never trigger this assertion
anyway, but if someone has a non standard use case, I see no reason
to make the program panic.
If a user doesn't care that the manifest failed to be written, they can
simply ignore it. The program will still work; that particular cache
item will simply not be cached.
It checks whether the cache will respond correctly to inputs that don't
initially depend on filesystem state. In that case, we have to check
for the existence of a manifest file, instead of relying on reading the
list of entries to tell us if the cache is invalid.
Instead of releasing the manifest file when an error occurs, it is
only released when when `CacheHash.release` is called. This maps better
to what a zig user expects when they do `defer cache_hash.release()`.
A file handle is not the same thing as an inode index number.
Eventually the inode will be checked as well, but there needs to be
a way to get the inode in `std` first.
