UnZip Streams

[rstevens]

I'm receiving a stream over a WinSocket. If these come from a valid user they will be a zipped stream.

If the user is not valid, i.e someone tries to send miscellaneous characters to the port, how can I check that the stream is a valid stream that can be UnZipped?

Hope the question makes sense. If not, let me know and I'll try again...

[Kevin]

If you are a registered user, check KPZIPOBJ.PAS and you will see some definitions for headers. A zip file will start with a local header and that local header will start with a particular signature. You could check for that signature.

Kevin

[rstevens]

Is this the header record??

local_file_header = packed record
Signature: SignatureType;
version_needed_to_extract: WORD;
general_purpose_bit_flag: WORD;
compression_method: WORD;
last_mod_file_date_time: U_LONG;
crc32: U_LONG;
compressed_size: LongInt;
uncompressed_size: LongInt;
filename_length: WORD;
extra_field_length: WORD;
end;

and if so, how would I test it??

Thanks for your help Kevin

[Kevin]

Yes, you should test the first 4 bytes and they should be the signature. For standard zip files, this signature would be, as is defined in KPZCONST.PAS as

DEF_LOCSIG = $04034b50;

Kevin