This patch allows zlib to compile cleanly with the -Wcast-qual gcc
warning enabled, but only if ZLIB_CONST is defined, which adds
const to next_in and msg in z_stream and in the in_func prototype.
A --const option is added to ./configure which adds -DZLIB_CONST
to the compile flags, and adds -Wcast-qual to the compile flags
when ZLIBGCCWARN is set in the environment.
This avoids warnings in OpenBSD that apparently can't be turned
off whenever you link strcpy, strcat, or sprintf. When snprintf
isn't available, the use of the "unsafe" string functions has
always in fact been safe, since the lengths are all checked before
those functions are called.
We do not use strlcpy or strlcat, since they are not (yet) found on
all systems. snprintf on the other hand is part of the C standard
library and is very common.
The conversion to multi-byte will be locale-specific, but it's
better than nothing and is only to provide more information in the
error message returned by gz_error(). The conversion has no
effect on what's opened.
Also need to #include <stddef.h> for zlib.h, and need to workaround
the inability to use wide characters in constructed error messages
with zlib's interface.
Before, gzeof() would return true (accurately) when the last read request
went just up to the end of the uncompressed data. In the analogous case,
feof() would return false, only returning true when a read request goes
past the end of the file. This patch corrects gzeof() to behave in the
same way as feof(), as noted in the zlib.h documentation.
Before this fix, gzread() would lose data if a premature end of file
was encountered. This prevented gzread() from being used on a file
that was being written concurrently. Now gzread() returns all of the
data it has available before indicating a premature end of file.
This also changes the error returned on a premature end of file from
Z_DATA_ERROR to Z_BUF_ERROR. This allows the user to determine if
the error is recoverable, which it is if Z_BUF_ERROR is returned. If
a Z_DATA_ERROR is returned, then the error is not recoverable.
This patch replaces the functionality of a previous patch that fixed
reading through an empty gzip stream in a concatenation of gzip
streams.
To implement this fix, a noticeable rewrite of gzread.c was needed.
The patch has the added advantage of using inflate's gzip processing
instead of replicating the functionality in gzread.c. This makes the
gz code a little simpler.
