This is attempt to simplify porting programs to rockbox (as plugins).
Currently this compat layer implements:
fopen(), fclose(), fflush(), fread(), fwrite(), fseek(), fseeko(),
ftell(), ftello(), fgetc(), ungetc(), fputc(), fgets(), clearerr(),
ferror(), feof(), fprintf()

In order to use it you need to include in ported sources
"lib/stdio_compat.h"

Change-Id: I5add615dd19c5af9c767ccbfb1bd5a4e466741cb

New support as well as some buggy support fixed.

Still no floating point support if ever that would be desired.

Support (*):
* Flags: '-', '+', ' ', '#', '0'

* Width and precision: 'n', '.n', '*' and '.*'

* Length modifiers: 'hh', 'h', 'j', 'l', 'll', 't', 'z'

* Radix: 'c', 'd', 'i', 'n', 'o', 'p/P', 's', 'u', 'x/X'

(*) Provision exists to switch lesser-used stuff on or off or when
certain functionality isn't desired (bootloader?). The compulsory
radixes are everything but 'o', 'n', 'p/P' and 'x/X' with length
modifiers being optional. The default setup is 'l', 'z', 'c', 'd',
'p/P', 's', 'u', 'x/X'.

* Move fdprintf() to its own file. It was in a strange place.

* Make callers compatible and fix a couple snprintf() bugs while
at it.

Could smush it down in size but I'm gonna get over the binsize
neurosis and just the let optimizer do its thing.

Change-Id: Ibdc613a9b6775802c188b29b9dd46c568c94f7c3

Unlike the current code, it does no looping to count days or do
table lookups, which means running time doesn't increase with year
or month. A good thing if it's call a lot, especially if the
algorithm were asked to compute dates centuries or more from the
epoch start.

As a bonus, handles negative time values.

Change-Id: I198a23daf621e40623e6b44dacf2387078b4db9c

Some drivers set tm_wday just fine and do not need it coerced to
be correct. Others set tm_yday, so don't overwrite what the driver
sets; just zero it inside if it can't fill the field. Move calls
to set_day_of_week() to the sorts of drivers that presumably
required the hammer (FS#11814) in get_time() where the weekday
isn't locked to the date.

Change-Id: Idd0ded6bfc9d9f48fcc1a6074068164c42fcf24a

defined in mingw environments.

Renamed defines of UNALIGNED to ROCKBOX_UNALIGNED so that they don't
conflict with definitions in mingw32 cross-compiling environments
(defined in _mingw.h).

Change-Id: I369848c0f507e6bf5ff9ab4a60663bbbda6edc52

Checked with upstream lynx source code and the
second calculation line is the upstream one, too.
(In fact I diffed the whole function to check for changes)

cppcheck reported:
[rockbox/firmware/libc/mktime.c:43] -> [rockbox/firmware/libc/mktime.c:44]: (performance) Variable 'result' is reassigned a value before the old one has been used.

Change-Id: Ia04c5f55da7d86cd74cff4fce675a9c85ddce3e2

Change-Id: I21c9c21fd664fb11bc8496ace4a389f535a030d6

A GNU extension that returns dst + size instead of dst. It's a nice
shortcut when copying strings with a known size or back-to-back blocks
and you have to do it often.

May of course be called directly or alternately through
__builtin_mempcpy in some compiler versions.

For ASM on native targets, it is implemented as an alternate entrypoint
to memcpy which adds minimal code and overhead.

Change-Id: I4cbb3483f6df3c1007247fe0a95fd7078737462b

This patch redoes the filesystem code from the FAT driver up to the
clipboard code in onplay.c.

Not every aspect of this is finished therefore it is still "WIP". I
don't wish to do too much at once (haha!). What is left to do is get
dircache back in the sim and find an implementation for the dircache
indicies in the tagcache and playlist code or do something else that
has the same benefit. Leaving these out for now does not make anything
unusable. All the basics are done.

Phone app code should probably get vetted (and app path handling
just plain rewritten as environment expansions); the SDL app and
Android run well.

Main things addressed:
1) Thread safety: There is none right now in the trunk code. Most of
what currently works is luck when multiple threads are involved or
multiple descriptors to the same file are open.

2) POSIX compliance: Many of the functions behave nothing like their
counterparts on a host system. This leads to inconsistent code or very
different behavior from native to hosted. One huge offender was
rename(). Going point by point would fill a book.

3) Actual running RAM usage: Many targets will use less RAM and less
stack space (some more RAM because I upped the number of cache buffers
for large memory). There's very little memory lying fallow in rarely-used
areas (see 'Key core changes' below). Also, all targets may open the same
number of directory streams whereas before those with less than 8MB RAM
were limited to 8, not 12 implying those targets will save slightly
less.

4) Performance: The test_disk plugin shows markedly improved performance,
particularly in the area of (uncached) directory scanning, due partly to
more optimal directory reading and to a better sector cache algorithm.
Uncached times tend to be better while there is a bit of a slowdown in
dircache due to it being a bit heavier of an implementation. It's not
noticeable by a human as far as I can say.

Key core changes:
1) Files and directories share core code and data structures.

2) The filesystem code knows which descriptors refer to same file.
This ensures that changes from one stream are appropriately reflected
in every open descriptor for that file (fileobj_mgr.c).

3) File and directory cache buffers are borrowed from the main sector
cache. This means that when they are not in use by a file, they are not
wasted, but used for the cache. Most of the time, only a few of them
are needed. It also means that adding more file and directory handles
is less expensive. All one must do in ensure a large enough cache to
borrow from.

4) Relative path components are supported and the namespace is unified.
It does not support full relative paths to an implied current directory;
what is does support is use of "." and "..". Adding the former would
not be very difficult. The namespace is unified in the sense that
volumes may be specified several times along with relative parts, e.g.:
"/<0>/foo/../../<1>/bar" :<=> "/<1>/bar".

5) Stack usage is down due to sharing of data, static allocation and
less duplication of strings on the stack. This requires more
serialization than I would like but since the number of threads is
limited to a low number, the tradoff in favor of the stack seems
reasonable.

6) Separates and heirarchicalizes (sic) the SIM and APP filesystem
code. SIM path and volume handling is just like the target. Some
aspects of the APP file code get more straightforward (e.g. no path
hashing is needed).

Dircache:
Deserves its own section. Dircache is new but pays homage to the old.
The old one was not compatible and so it, since it got redone, does
all the stuff it always should have done such as:

1) It may be update and used at any time during the build process.
No longer has one to wait for it to finish building to do basic file
management (create, remove, rename, etc.).

2) It does not need to be either fully scanned or completely disabled;
it can be incomplete (i.e. overfilled, missing paths), still be
of benefit and be correct.

3) Handles mounting and dismounting of individual volumes which means
a full rebuild is not needed just because you pop a new SD card in the
slot. Now, because it reuses its freed entry data, may rebuild only
that volume.

4) Much more fundamental to the file code. When it is built, it is
the keeper of the master file list whether enabled or not ("disabled"
is just a state of the cache). Its must always to ready to be started
and bind all streams opened prior to being enabled.

5) Maintains any short filenames in OEM format which means that it does
not need to be rebuilt when changing the default codepage.

Miscellaneous Compatibility:
1) Update any other code that would otherwise not work such as the
hotswap mounting code in various card drivers.

2) File management: Clipboard needed updating because of the behavioral
changes. Still needs a little more work on some finer points.

3) Remove now-obsolete functionality such as the mutex's "no preempt"
flag (which was only for the prior FAT driver).

4) struct dirinfo uses time_t rather than raw FAT directory entry
time fields. I plan to follow up on genericizing everything there
(i.e. no FAT attributes).

5) unicode.c needed some redoing so that the file code does not try
try to load codepages during a scan, which is actually a problem with
the current code. The default codepage, if any is required, is now
kept in RAM separarately (bufalloced) from codepages specified to
iso_decode() (which must not be bufalloced because the conversion
may be done by playback threads).

Brings with it some additional reusable core code:
1) Revised file functions: Reusable code that does things such as
safe path concatenation and parsing without buffer limitations or
data duplication. Variants that copy or alter the input path may be
based off these.

To do:
1) Put dircache functionality back in the sim. Treating it internally
as a different kind of file system seems the best approach at this
time.

2) Restore use of dircache indexes in the playlist and database or
something effectively the same. Since the cache doesn't have to be
complete in order to be used, not getting a hit on the cache doesn't
unambiguously say if the path exists or not.

Change-Id: Ia30f3082a136253e3a0eae0784e3091d138915c8
Reviewed-on: http://gerrit.rockbox.org/566
Reviewed-by: Michael Sevakis <jethead71@rockbox.org>
Tested: Michael Sevakis <jethead71@rockbox.org>

We redefine the top-level macros to our own in order to maintain
compatibility with compound initializers by wrapping the mid or low
level definitions from the OS header.

This allows, hopefully optimized, macros from the host OS's headers to
be used when building any hosted target obviating the need for
NEED_GENERIC_BYTESWAPS unless the target simply doesn't define its
own optimized versions (MIPS!).

Throw in some 64-bit swaps for completeness' sake; they generate no code
if not yet used anyway.

Change-Id: I21b384b55fea46833d01ea3cad1ad8952ea01a11