[Vxl-users] Android Port

[David M. <mck...@gm...>]

Hi,
I have started an Android port, I am using android-cmake which seems to
allow VXL to build for the most part with the proper arm architecture
switches straight out of the box.

I have run into four problems so far, solving two of them and the remaining
two are unsolved.

Firstly, as you are building for a remote platform is not clear to your
build architecture what the endian type is.  I have added the following
lines to the root level CMakeLists.txt around line 33

OPTION(VXL_CHECK_ENDIAN "Check for target platform endian type?" YES)
IF(NOT VXL_CHECK_ENDIAN)
OPTION(VXL_IS_BIG_ENDIAN "Whether the target platform endian type is big?"
YES)
IF(VXL_IS_BIG_ENDIAN)
SET(VXL_BIG_ENDIAN 1)
SET(VXL_LITTLE_ENDIAN 0)
ELSE(VXL_IS_BIG_ENDIAN)
SET(VXL_BIG_ENDIAN 0)
SET(VXL_LITTLE_ENDIAN 1)
ENDIF(VXL_IS_BIG_ENDIAN)
ENDIF(NOT VXL_CHECK_ENDIAN)

The idea here is that if you know the endian type of the remote platform you
can just set it as a cmake option, the naming of these variable may not be
ideal...

Secondly the file search.h does not exist in the Android NDK consequently
there are problems when building tiff support. Due to this the following
edits are made to v3p/tiff/tif_config.h

/* Define to 1 if you have the <search.h> header file. */
#ifndef ANDROID
#define HAVE_SEARCH_H 1
#endif // ANDROID

There are two further problems that I have hit that I have not been able to
get around yet mostly because they will require some changes to vcl and more
specifically the support of std C functions within.  There is an absence of
snprintf (from vul_url) and the function __errno_location
(vil_nitf2_typed_field_formatter.cxx) for the Android platform.

A fix to the snprintf would be to provide this definition somewhere :

*int*snprintf(*char* *str, size_t n, *const* *char* *fmt, ...)*{*
  va_list ap;
	*int* ret;
	*char* dummy;
	FILE f;
	*struct* __sfileext fext;

	/* While snprintf(3) specifies size_t stdio uses an int internally */
	*if* (n > INT_MAX)
		n = INT_MAX;
	/* Stdio internals do not deal correctly with zero length buffer */
	*if* (n == 0) *{*
		str = &dummy;
		n = 1;
	*}*
	_FILEEXT_SETUP(&f, &fext);
	f._file = -1;
	f._flags = __SWR | __SSTR;
	f._bf._base = f._p = (*unsigned* *char* *)str;
	f._bf._size = f._w = n - 1;
	va_start(ap, fmt);
	ret = vfprintf(&f, fmt, ap);
  va_end(ap);
	*f._p = '\0';
	*return* (ret);*}*


Another issue I have read about is the packing of bytes in structs

struct {
unsigned char something;
int else
};

Would result in a sizeof() = 8 not 5 on a typical system, I don't know if
this is problematic or not.

As far as I can tell these are the only issues in the core libraries and I
suspect that there are probably some straight forward solutions for those of
you that understand vcl adequately.

Does anyone have some ideas about solutions?  Or is there any general
interest in adding in these support fixes to the SVN?

Cheers,
David McKinnon...