How does one find the start of the “Central Directory” in zip files?

Question

Wikipedia has an excellent description of the ZIP file format, but the \"central directory\" structure is confusing to me. Specifically this:

This orderin

Answer 1

I was implementing zip archive support some time ago, and I search last few kilobytes for a end of central directory signature (4 bytes). That works pretty good, until somebody will put 50kb text into comment (which is unlikely to happen. To be absolutely sure, you can search last 64kb + few bytes, since comment size is 16 bit). After that, I look up for zip64 end of central dir locator, that's easier since it has fixed structure.