class TZIPFile: public TArchiveFile

TZIPFile

This class describes a ZIP archive file containing multiple
sub-files. Typically the sub-files are ROOT files. Notice that
the ROOT files should not be compressed when being added to the
ZIP file, since ROOT files are normally already compressed.
Such a ZIP file should be created like:

zip -n root multi file1.root file2.root

which creates a ZIP file multi.zip.

A ZIP archive consists of files compressed with the popular ZLIB
compression algorithm. The archive format is used among others by
PKZip and Info-ZIP. The compression algorithm is also used by
GZIP and the PNG graphics standard. The format of the archives is
explained briefly below. This class provides an interface to read
such archives.

A ZIP archive contains a prefix, series of archive members
(sub-files), and a central directory. In theory the archive could
span multiple disks (or files) with the central directory of the
whole archive on the last disk, but this class does not support
such multi-part archives. The prefix is only used in self-extracting
executable archive files.

The members are stored in the archive sequentially, each with a
local header followed by the (optionally) compressed data; the local
header describes the member, including its file name and compressed
and real sizes. The central directory includes the member details
again, plus allows an extra member comment to be added. The last
member in the central directory is an end marker that can contain
a comment for the whole archive. Both the local header and the
central directory can also carry extra member-specific data; the
data in the local and global parts can be different.
The fact that the archive has a global directory makes it efficient
and allows for only the reading of the desired data, one does not
have to scan through the whole file to find the desired sub-file.

Once the archive has been opened, the client can query the members
and read their contents by asking the archive for an offset where
the sub-file starts. The members can be accessed in any order.