well, oops. on slow io (as can happen with ssh remote builders) we could
have extended a nar read buffer past what was actually read, injecting a
span of zeroes into the read buffer where we requested some data but got
a partial result instead. also add some tests that would've caught this.
Change-Id: I67aa06b4715aeec6a5bdacaafa9b79849e664e2f
sadly this is a visitor-only interface; async generators are not yet a
thing and preliminary benchmarks say that overhead would be too large.
Change-Id: I0460d18eba94441cf3101d46bfffdb69cdda81d1
we'll use this in NarAccessor to provide actually safe indexing of
archives. NarAccessor currently is not fully correct: it relies on
the parser not buffering anything to produce correct file offsets,
but only the nar implementation itself can reasonably expect that.
Change-Id: I64f300b86d8844b876a3ace723546ea7d7b4628b
this is where they should've been from the start, but during the first
rewrite it made little sense to move them. we have bigger plans today,
so we'll finally clean that up too. note the `Map` transform type that
is needed to make the current macros work. it shall be only temporary.
Change-Id: I928d197dbfe27b68cf8634d149c3259e86fbf123
eldritch horrors