Pullreq FAT improvements
* NuttX: Add CONFIG_FAT_LFN_ALIAS_HASH to speed up creating long filenames.
Long filenames on FAT filesystems have associated 8.3 character alias
short filenames. The traditional form of these is FILENA~1.EXT with
a running count of the number of similar names. However creating this
unique count can take several seconds if there are many similarly named
files in the directory. Enabling FAT_LFN_ALIAS_HASH uses an alternative
format of FI0123~1.TXT where the four digits are a hash of the original
filename. This method is similar to what is used by Windows 2000 and
later.
* NuttX: Add CONFIG_FAT_LFN_ALIAS_TRAILCHARS alternative format for 8.3 filenames.
Traditional format for long filename 8.3 aliases takes first 6
characters of long filename. If this option is set to N > 0,
NuttX will instead take first 6-N and last N characters to form
the short name. This is useful for filenames like "datafile12.txt"
where the first characters would always remain the same.
* NuttX: FAT32: Fix file date corruption in fat_truncate().
* NuttX: if SD card wait seems to be a long one, give time for other threads to run.
Approved-by: GregoryN <gnutt@nuttx.org>
Squashed commit of the following:
fs/fat/fs_fat32util.c: Most costmetic naming MBR to FBR in numerous locations. Change some ferr macros to fwarn. Use FBR macros insteac of MBR macros.
Add definitions for the FAT boot record (FBR).
fs/fat: Clean up some name BS_ and MBR_ refer to the same record and should use the same naming (MBR_).
Squashed commit of the following:
fs/fat: Resolves issues with truncating the cluster chain when shrinking files via ftruncate().
fs/fat: First cut at implementation file shrinkage logic needed to support ftruncate(). Certainly shrinks the file size but it does not appear to correctly disconnect the cluster chains.
fs/fat: Restructure some functions in files to better support forthcoming file shrinkage logic. Put framework for file shrinkage in place. That logic is incomplete on initial commit.
This commit backs out most of commit b4747286b1. That change was added because sem_wait() would sometimes cause cancellation points inappropriated. But with these recent changes, nxsem_wait() is used instead and it is not a cancellation point.
In the OS, all calls to sem_wait() changed to nxsem_wait(). nxsem_wait() does not return errors via errno so each place where nxsem_wait() is now called must not examine the errno variable.
In all OS functions (not libraries), change sem_wait() to nxsem_wait(). This will prevent the OS from creating bogus cancellation points and from modifying the per-task errno variable.
sched/semaphore: Add the function nxsem_wait(). This is a new internal OS interface. It is functionally equivalent to sem_wait() except that (1) it is not a cancellation point, and (2) it does not set the per-thread errno value on return.
sched/semaphore: Add nxsem_post() which is identical to sem_post() except that it never modifies the errno variable. Changed all references to sem_post in the OS to nxsem_post().
sched/semaphore: Add nxsem_destroy() which is identical to sem_destroy() except that it never modifies the errno variable. Changed all references to sem_destroy() in the OS to nxsem_destroy().
libc/semaphore and sched/semaphore: Add nxsem_getprotocol() and nxsem_setprotocola which are identical to sem_getprotocol() and set_setprotocol() except that they never modifies the errno variable. Changed all references to sem_setprotocol in the OS to nxsem_setprotocol(). sem_getprotocol() was not used in the OS
