readme

压缩算法的源代码

Notes about MS-DOS executables and compilers:

 - Borland start-up code is reported to switch the screen mode auto-
   matically if it's not 80 columns (or possibly 40) and either 25, 43 
   or 50 lines.  In particular, extended modes such as 100x40 are not
   retained.

 - Borland start-up code also uses interrupt 1Ah, causing incorrect
   behavior (including lock-ups) on some Japanese MS-DOS machines such
   as the Fujitsu FMR series, which lack this interrupt.

 - Some(?) Borland compilers are apparently incapable of putting static
   data into far memory; this means all of UnZip's strings are in near
   memory, and there is not enough room to enable ZipInfo in the small
   memory model.  Even if strings are in far memory, the *code* segment
   produced by Borland compilers is now too big for one segment.  The
   large memory model is therefore the default for Borland compilers, but
   it may be possible to compile in the medium model as well (not tested).

 - Older Borland compilers do not understand source files with Unix
   line-endings (LF rather than CR/LF).  Use "flip" or a similar utility
   to convert the line endings before compiling, or take a look at the
   Borland.fix file in the UnZip source distribution.

 - Microsoft C 5.1 large-model code is more than an order of magnitude
   slower than the identical code compiled with MSC 6 or 7 (a factor of
   15 in our tests, actually).  This may be due to a lousy optimizer or
   lousy libraries; regardless, since UnZip is hovering at the doorstep
   of the large memory model, we recommend upgrading to a later version
   of the compiler.

For these reasons, Info-ZIP's distributed versions of the 16-bit MS-DOS 
executables are compiled with MSC 6 or 7.

 - The default wildcard ("globbing") behavior of djgpp/go32 is disabled
   by default in UnZip, but this can be overridden if the GO32 environment
   variable is set to "glob".  This will cause UnZip to fail with various
   odd errors about "filename not matched" and the like; to avoid this, set
   the GO32 variable to "noglob" or unset it altogether.  (The documented
   method of avoiding this by quoting wildcards with single quotes was 
   buggy in djgpp 1.11 but is reported fixed in 1.12; not tested.)

 - djgpp's handling of timezones, necessary for the correct conversion of
   MS-DOS filetimes to those used in the Unix-like C library, is completely
   broken in djgpp 1.12 and probably earlier versions as well.  It is fixed
   (or very close to it) in the most recent 1.12m1 beta, so be sure to up-
   grade to 1.12m1 before compiling.  Otherwise UnZip's -f and -u (freshen/
   update) functions will not work correctly.

 - emx+gcc's DOS extender does not understand DPMI, and while there is an
   alternative extender called RSX available (found in dpmigcc4.zip as of
   August 1994), its setup is somewhat kludgy when the local memory manager
   supports both DPMI and VCPI (or something else).  It's also not yet as
   widely known or available as djgpp.

For these reasons Info-ZIP's distributed 32-bit MS-DOS executables are com-
piled with djgpp 1.12m1.  These are stand-alone programs; the "go32" DOS 
extender is included inside the executables.  They generally run up to twice
as fast as the 16-bit versions, but they only work on 386's and above.  In 
some cases they're actually slower.  If this is the case for you, first try 
running under plain DOS, after removing any memory manager in your config.sys
and rebooting, to check if the slowdown is due to your memory manager.  (Ac-
cording to notes found in another package, there was a known conflict between 
the go32 extender and QEMM's DPMI; this was apparently just fixed in QEMM 
7.04/QDPMI 1.05, but if you still have an older version (1.03 or 1.01), add 
"set GO32=nodpmi" to your autoexec.bat to avoid the conflict.)  There may 
also be a problem with the time spent by the djgpp runtime creating and de-
leting a swap file.  If you use SMARTDRV or another disk cache, make sure 
that writes are also cached.

If you already have djgpp 1.12m1 or later (or, more specifically, go32.exe
1.12m1 or later somewhere in your PATH), you can remove go32.exe from
unzip386.exe to get a smaller executable:

	exe2coff unzip386.exe
	coff2exe unzip386
	del unzip386

As noted above, go32/djgpp has its own wildcard-expansion routines which
are disabled in UnZip by default because of incompatibilities with UnZip's
own wildcards.  Stripping the go32 extender may cause go32's wildcards to
be re-enabled; in this case you must set GO32 as follows for UnZip to work
correctly:

	set GO32=noglob

With this setting unzip386.exe behaves just like unzip.exe.

For other problems related to DJGPP, read the documentation provided in
oak.oakland.edu:/pub/msdos/djgpp/djdev112.zip.  If a problem occurs with 
unzip386.exe, check first if it also occurs with unzip.exe before reporting 
it.


GRR 940828