This may seem like a crazy idea, but maybe there should be a new thread since 5.0 has been released, and many things are different from prior examples. A good Q&A in the fresh thread would make it much simpler for new people.QUOTE said:
Yes, I can partially unzip the file, but the only thing is some people like to keep the original zip in tact, so partially unzipping would be useless, as there's no way to tell if the first item is the rom or not... I could have it check, but it would still have to unzip to the point to where it finds the rom. No worries, doing the full unzip to identify the games should be fineIt's pretty quick to unzip anyways.
You may not need to decompress anything.
Take a look at the zip archive specification.
http://www.pkware.com/documents/casestudies/APPNOTE.TXT
The overall zip archive format is as such:
Code:Â Â[local file header 1] Â Â[file data 1] Â Â[data descriptor 1] Â Â. Â Â. Â Â. Â Â[local file header n] Â Â[file data n] Â Â[data descriptor n] Â Â[archive decryption header] Â Â[archive extra data record] Â Â[central directory] Â Â[zip64 end of central directory record] Â Â[zip64 end of central directory locator] Â Â[end of central directory record]
Each file compressed within a zip archive has a header and a descriptor that encapsulate the compressed data.
Here's the header info.
CODE    Âlocal file header signature   4 bytes Â(0x04034b50)
   Âversion needed to extract    2 bytes
   Âgeneral purpose bit flag    Â2 bytes
   Âcompression method       Â2 bytes
   Âlast mod file time       Â2 bytes
   Âlast mod file date       Â2 bytes
   Âcrc-32             Â4 bytes
   Âcompressed size         4 bytes
   Âuncompressed size        4 bytes
   Âfile name length        Â2 bytes
   Âextra field length       Â2 bytes
   Âfile name (variable size)
   Âextra field (variable size)
Yes, I can partially unzip the file, but the only thing is some people like to keep the original zip in tact, so partially unzipping would be useless, as there's no way to tell if the first item is the rom or not... I could have it check, but it would still have to unzip to the point to where it finds the rom. No worries, doing the full unzip to identify the games should be fineIt's pretty quick to unzip anyways.
You may not need to decompress anything.
Take a look at the zip archive specification.
http://www.pkware.com/documents/casestudies/APPNOTE.TXT
The overall zip archive format is as such:
Code:[local file header 1] [file data 1] [data descriptor 1] . . . [local file header n] [file data n] [data descriptor n] [archive decryption header] [archive extra data record] [central directory] [zip64 end of central directory record] [zip64 end of central directory locator] [end of central directory record]
Each file compressed within a zip archive has a header and a descriptor that encapsulate the compressed data.
Here's the header info.
Code:local file header signature 4 bytes (0x04034b50) version needed to extract 2 bytes general purpose bit flag 2 bytes compression method 2 bytes last mod file time 2 bytes last mod file date 2 bytes crc-32 4 bytes compressed size 4 bytes uncompressed size 4 bytes file name length 2 bytes extra field length 2 bytes file name (variable size) extra field (variable size)
All headers start with 0x04034b50 (or 0x0504b0304 in little-endian)
The CRC32 value in the header is the CRC of the uncompressed file.
If you wrote a function that searched all the headers in a zip archive for filenames ending in .NDS, you could find the .NDS file no matter if it was the first or last file in the archive. This requires no unzipping, either. As shown above, the filenames are embedded in the zip file. This would be a rather quick search because any other file in the archive is probably less than 100k. You'd only have to stop at the first NDS file, too.
Once you know where the NDS file is located in the archive, you can do one of two things:
1. Pull out the CRC32 value from the header and use it to identify the ROM. It should match up with what's in your database.
2. Set up a stream with the starting point set at the beginning of the compressed data. Then, use e-CryptIt's zStreamReader class to read this stream. The read method of the zStreamReader class lets you specify the number of bytes you want to pull from the stream. In other words, you can specify a specific number of bytes decompress. You just need to decompress the NDS file's header into RAM.
- N
EDIT: I apologize if I'm going overboard in trying to help you with this issue. It just got me thinking because I'm starting to use zips in my own personal applications.
@Logan: My family and I have been sick the past few days so it's been difficult to get programming done. My wife's been sick for a week now and she hasn't been getting any better yet... No worries, we'll see how things go over the next couple days. Today I'll try and get some more coding done, and tomorrow, well, tomorrow I'll be playing Guitar Hero 3 regardless of being sick or not
