This now searches the memory in blocks, which should be slightly more
efficient. However, it doesn't make much difference (e.g. ~1% in LZMA
compression) in most real-world applications, as the non-hint function
is more expensive by orders of magnitude.
This factors out a lot of complicated math into somewhat understandable
functions.
While at it, rename `next_read_span_with_seekback` to
`next_seekback_span` to keep the naming consistent and to avoid making
function names any longer.
The "operation modes" of this function have very different focuses, and
trying to combine both in a way where we share the most amount of code
probably results in the worst performance.
Instead, split up the function into "existing distances" and "no
existing distances" so that we can optimize either case separately.
We will be adding extra logic to the CircularBuffer to optimize
searching, but this would negatively impact the performance of
CircularBuffer users that don't need that functionality.
In a similar fashion to what have been done with `fill_from_stream`,
this new method allows to write CircularBuffer's data to a Stream
without additional copies.
Instead of reading bytes from the output stream into a buffer, just to
immediately write them back out, we can skip the middle-man and copy the
bytes directly into the output buffer.
When reading, we currently only fill a BufferedStream's buffer when it
is empty, and only with 1 KB of data. This means that while the buffer
defaults to a size of 16 KB, at least 15 KB is always unused.
This parameter allows to start searching after an offset. For example,
to resume a search.
It is unfortunately a breaking change in API so this patch also modifies
one user and one test.
The previously defined operator was swap-based. With the defaulted
implementation, both integers are now copied, but it doesn't matter as
only the `ByteBuffer` allocates memory (i.e. non-null integers values
won't affect the destruction).
The class is very similar to `CircularDuplexStream` in its behavior.
Main differences are that `CircularBuffer`:
- does not inherit from `AK::Stream`
- uses `ErrorOr` for its API
- is heap allocated (and OOM-Safe)
This patch also add some tests.
