We now read the data into a (sometimes stack-allocated) byte array and slice it up with BinaryPrimitives.
This reduces the number of reads and writes required to read and write a ZipArchive. It also makes future work to enable async APIs easier, since BinaryReader and BinaryWriter lack this support.
Also changed approach to reading central file directory headers. Rather than performing X reads per header, we read 4KB of data at a time and look for all applicable headers in that data. This should improve performance when dealing with many small files.

This allowed the removal of the ArchiveReader property from ZipArchive.

Now pooling the file IO buffers and the temporary buffers for extra fields of the CD file header (which would otherwise be allocated and deallocated in a loop.)

This handles 64x entries with 19-character filenames (and thus, 65-byte file headers.) As a result, it straddles two 4KB read buffers.

Also corrected the seek logic while reading the central directory header

…ead-write

The buffer returned from the ArrayPool contained older data (including a ZIP header.) When reading the last chunk of the file (i.e a chunk which was less than BackwardsSeekingBufferSize) the buffer's Span wasn't resized to account for this.
SeekBackwardsToSignature would thus find the older data, try to seek beyond the end of the stream and fail to read the file.