GZP

Synopsis

HELP:   Read ZLIB/GZIP/RCF1950-2 compressed data
TYPE:   OBJECT
SYNTAX: GZP(MEMBER='str',BUFSIZ=num,SKPORG)

Description

The GZIP converter can be used to compress or decompress data streams.

The result of a compression is a binary block. The result of a decompression can be text, XML, a base encoding or binary data. Record boundaries are lost. Please use delimiters, length fields or fixed length data if records must be exchanged.

The GZIP decompression can read all supported formats of zlib and writes RFC1952/51/50-compliant data streams. If a IBM ZEDC acceleration card is available and can be used, the ZEDC is used to save CPU time. In this case, however, the compression does not conform to RFC1951. The compressed data is encoded based on RFC1950 and the file format conforms to RCF1952.

For a checksummed GZIP header, an additional switch must be activated, because this feature is not supported by all GZIP implementations. The GZIP header is used to store meta information about the data, which can be used if FLAM is also used for decompression. This can be very useful to clearly define the character set, CCSID and other information about the data.

If no compression level is set and the data is marked as being without redundancy, then level 0 (copy) is used. Otherwise, the default level 6 is used.

Decompression of concatenated GZIP files is also possible. All concatenated files are decompressed into one file. It is also possible to decompress one specific member of this concatenation by specifying the member index of the file to be decompressed:

   filename/:memberindex
   filename/#memberindex

   test.gz/#3
   test.gz/:2

GZIP data streams are written to ZIP archives as compression mode 8. The GZIP header and trailer are replaced by a ZIP local file header. If a deflated file (compression mode 8) is read from a ZIP archive, it is converted to a GZIP data stream which can be inflated with this component.

Arguments