OS/390 is IBM's follow-on to MVS and includes a POSIX, XOPEN,
XPG4, build environment, a Unix-style filesystem (called HFS), and
a POSIX (Born) shell.  This port uses this environment and is a fairly
straight-forward port of ZIP's Unix port - but uses the existing EBCDIC
code.  This port does not work with non-HFS (traditional MVS)
filesystems.

I believe all my changes are isolated with #ifdef's.

Here's some text which might be useful for an OS390 README or
the manual.

ZIP for OS390 HFS datasets
--------------------------
Allows you to create ZIP archives from the OS/390 OpenEdition
command prompt.  This port uses standard Unix-style I/O routines
and only works with HFS files.

Usage
-----
By default, ZIP does not perform character-set translation, but has
options to make it easy to convert text files to be compatible with
other systems
  zip   zipfile list         # add the files in 'list' to archive 'zipfile'
  zip -a zipfile list        # same as above, but translate files to ASCII
  zip -al zipfile list       # same as above, translate linefeeds to DOS style
  zip -all zipfile list      # same as '-a', translate linefeeds to UNIX style

Build process
-------------
Assuming GNU make is available in your path and is called "gmake" (See
the  notes on Makefile changes below) and a C compiler is available as
"cc",  then type
  gmake -f unix/Makefile MAKE=gmake os390

If GNU make is not available, the existing makefile can create zip, but will
error on the other executable (zipsplit, zipcloak, zipnote) if you type
  make -f unix/Makefile os390

Overview of Changes
-------------------
The OS/390 port is treated as a variant of the Unix port.  EBCDIC support
was already implemented for CMS/MVS-batch ports.  The specific changes I
made are summarized below.

unix/Makefile - zip uses a unusual _.o target which IBM's make can't handle.
Since the Makefile has a macro called MAKE that is used for a recursive
call to make, I changed the MACRO to call "gmake" - GNU's make - which
can handle the _.o target.  If you don't have GNU make, you can
workaround by manually applying symlinks from whatever.c to whatever_.c.
Alternatively, the whatever_.o files could be explicitely added for os390.

I added an os390 target with appropriate defines.

zipup.c - added code (#ifdef OS390) to convert test to ASCII if -a flag
was set.

zip.c - changed logic which always used DOS-style newlines when -a was
set to be consistent with other port (DOS newlines if -l option)

zipfile.c - miscellaneous changes to force storing file names and
descriptions in ASCII in the zip directory. This makes zip files
portable  across all platforms. This in turn meant names did not
need to be translated when displaying messages.

zip.h - strtoasc was missing a closing parenthesis.

ebcdic.h - changed translation table to be consistent with current IBM
recommendations - exact same changes to ebcdic.h as in my unzip port.

tailor.h - define huge/far/near to be empty

unix/unix.c - substantial changes to deal with mode flags.  Under
the current XOPEN standards, some of the traditional unix file mode
bits need not be in fixed locations, but standard access macros must be
available to access the values.  The old unix.c code just picked up these
values and saved them as-is where unzip interpreted them.  Existing
Unix system provided the macros for XOPEN compliance, but left the flags
in their traditional locations.  OS/390 has a brand new filesystem which
is XOPEN compliant without revealing the positions of these flags.
To create the bitmask in the same format unzip expects, the macros are
tested one-by-one to set the appropriate bits.  This same logic should
work on any XOPEN system, but takes more instructions (I did test this
logic on Linux).