About Cabinet Format


About Cabinet Format

If you want more information about the Cabinet format, here are some extracts taken from Microsoft (R) documentation about Cabinet files:

What Is a Cabinet File?

A cabinet (.cab) file is a library of compressed files stored as a single file. Cabinet files are used to organize installation files that are copied to the user's system. A large compressed file can be spread over several .cab files.

For a number of years, Microsoft has used .cab files to compress software that was distributed on disks. Originally, these files were used to minimize the number of floppy disks shipped with a product. Today, .cab files are used to reduce the file size and the associated download time for Web content that is found on the Internet or on corporate intranet servers.

The Cabinet format

A folder is a continuous block of compressed data within a cabinet or cabinet set. Files in a cabinet archive can be compressed across their file boundaries as a single compression block. Compression ratios improve significantly when files are compressed together as opposed to individually. However, there's a trade-off between random access time to an individual file and compression ratio since an entire folder must be decompressHuffed to extract an item from it. Folders can span cabinets.

A file is an individual item in a cabinet. Files can span folders.

Microsoft Cabinet supports three lossless compression techniques: storing, MSZip, and LZX. Within a cabinet archive file, any combination of these techniques may be used. MSZip is essentially the same as the deflation compression method used by PKZip. LZX is an LZ77-based compression technique that uses static Huffman encoding. LZX uses more memory, but can produce better compression ratios than MSZip. Stored, of course, means the file is stored into the cabinet uncompressed.

More information on creating and using cabinet files can be found at http://msdn2.microsoft.com/en-us/library/ms974336.aspx (you can download the Microsoft (R) Cabinet SDK).