Create ZIP archives in streaming fashion, writing to a file descriptor. The output stream (file descriptor) does not need to be seekable and can be a pipe or a network socket. The entire archive contents does not need to be in memory at once.

zlib is required for deflate compression: https://www.zlib.net/

• Create a ZIP archive in a streaming fashion, writing to an output stream (file descriptor, pipe, network socket) without seeking.
• Compress the archive entries (using zlib). Support for the STORE and DEFLATE methods is included, others may be implemented through callback functions.
• Add ZIP64 structures as needed to support large (>4GB) archives.
• Simple creation of ZIP archives even if not streaming.

• Open/close files or sockets.
• Support advanced ZIP archive features (e.g. file attributes, encryption).
• Allow archiving of individual files/entries larger than 4GB, the total of all files can be larger than 4GB but not individual entries.

ZIP archive file/entry modifiation times are stored in UTC.

zs_init ()
  for each entry:
    zs_writeentry ()
zs_finish ()
zs_free ()

zs_init ()
  for each entry:
    zs_entrybegin ()
      for each chunk of entry:
        zs_entrydata()
    zs_entryend()
zs_finish ()
zs_free ()

Libraries such as libarchive (https://www.libarchive.org/) can create ZIP archives in a streaming fashion. But that is a lot of code, and a large dependency, to add to a project to get streaming ZIP archive creation. Other small ZIP creation projects exist but I could not find one that did not rely on seekable I/O streams and thus could not be used to write to a socket or pipe. I also needed a portable solution. This code depends only on zlib, which is itself very portable and commonly found in the base installation on many systems.

Simple ZIP archive creation in about 1000 lines of code, ready to be embedded.