CRC-32 field in zip

Question

I am designing a zip-unzip utility using C. There is a crc-32 code field. Is it of compressed data or uncompressed data?

Answer 1

It is the CRC-32 of the uncompressed data. In other words, it would be the CRC-32 of the file's original contents before being compressed. Zlib has a minizip contribution which is a small zip/unzip implementation written in C. In zip.c you can see in the function zipWriteInFileInZip that it is generating the crc of the buffer passed in that should contain the file's original contents.