Entries are compressed and written out as they are added, so the archive is
never held in memory: a backup of a 50 GB file store needs no more memory
than a few buffers, whatever its size. Deflation runs on libuv's thread
pool (zlib's streaming API), and the whole writer is driven from the zip
worker thread, so nothing here competes with the server's event loop.
Sizes and CRCs are not known until an entry has been written, so entries
carry a data descriptor (general purpose bit 3) instead. Entries larger
than ZIP64_THRESHOLD are written in zip64 format, which lifts the 4 GiB
limit on entry and archive size.
A streaming ZIP writer.
Entries are compressed and written out as they are added, so the archive is never held in memory: a backup of a 50 GB file store needs no more memory than a few buffers, whatever its size. Deflation runs on libuv's thread pool (zlib's streaming API), and the whole writer is driven from the zip worker thread, so nothing here competes with the server's event loop.
Sizes and CRCs are not known until an entry has been written, so entries carry a data descriptor (general purpose bit 3) instead. Entries larger than ZIP64_THRESHOLD are written in zip64 format, which lifts the 4 GiB limit on entry and archive size.