Rewrite filesystem code (WIP)

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>

1 files changed, 833 insertions, 0 deletions

diff --git a/uisimulator/common/filesystem-sim.c b/uisimulator/common/filesystem-sim.c
new file mode 100644
index 0000000000..766beb3fda
--- /dev/null
+++ b/uisimulator/common/filesystem-sim.c
@@ -0,0 +1,833 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ * $Id$
+ *
+ * Copyright (C) 2002 Daniel Stenberg
+ * Copyright (C) 2014 Michael Sevakis
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ****************************************************************************/
+#define RB_FILESYSTEM_OS
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdarg.h>
+#include <time.h>
+#include <errno.h>
+#include <limits.h>
+#include "config.h"
+#include "system.h"
+#include "file.h"
+#include "dir.h"
+#include "file_internal.h"
+#include "pathfuncs.h"
+#include "string-extra.h"
+#include "debug.h"
+
+#ifndef os_fstatat
+#define USE_OSDIRNAME /* we need to remember the open directory path */
+#endif
+
+extern const char *sim_root_dir;
+
+/* Windows (and potentially other OSes) distinguish binary and text files.
+ * Define a dummy for the others. */
+#ifndef O_BINARY
+#define O_BINARY 0
+#endif
+
+struct filestr_desc
+{
+    int  osfd;              /* The host OS file descriptor */
+    bool mounted;           /* Is host volume still mounted? */
+#ifdef HAVE_MULTIVOLUME
+    int  volume;            /* The virtual volume number */
+#endif
+} openfiles[MAX_OPEN_FILES] =
+{
+    [0 ... MAX_OPEN_FILES-1] = { .osfd = -1 }
+};
+
+static struct filestr_desc * alloc_filestr(int *fildesp)
+{
+    for (unsigned int i = 0; i < MAX_OPEN_FILES; i++)
+    {
+        struct filestr_desc *filestr = &openfiles[i];
+        if (filestr->osfd < 0)
+        {
+            *fildesp = i;
+            return filestr;
+        }
+    }
+
+    return NULL;
+}
+
+static struct filestr_desc * get_filestr(int fildes)
+{
+    struct filestr_desc *filestr = &openfiles[fildes];
+
+    if ((unsigned int)fildes >= MAX_OPEN_FILES || filestr->osfd < 0)
+        filestr = NULL;
+    else if (filestr->mounted)
+        return filestr;
+
+    errno = filestr ? ENXIO : EBADF;
+    DEBUGF("fildes %d: %s\n", fildes, strerror(errno));
+    return NULL;
+}
+
+struct dirstr_desc
+{
+    int               osfd;          /* Host OS directory file descriptor */
+    bool              osfd_opened;   /* Host fd is another open file */
+    OS_DIR_T          *osdirp;       /* Host OS directory stream */
+#ifdef USE_OSDIRNAME
+    char              *osdirname;    /* Host OS directory path */
+#endif
+    struct sim_dirent entry;         /* Rockbox directory entry */
+#ifdef HAVE_MULTIVOLUME
+    int               volume;        /* Virtual volume number */
+    int               volumecounter; /* Counter for root volume entries */
+#endif
+    bool              mounted;       /* Is the virtual volume still mounted? */
+} opendirs[MAX_OPEN_DIRS];
+
+static struct dirstr_desc * alloc_dirstr(void)
+{
+    for (unsigned int i = 0; i < MAX_OPEN_DIRS; i++)
+    {
+        struct dirstr_desc *dirstr = &opendirs[i];
+        if (dirstr->osdirp == NULL)
+            return dirstr;
+    }
+
+    return NULL;
+}
+
+static struct dirstr_desc * get_dirstr(DIR *dirp)
+{
+    struct dirstr_desc *dirstr = (struct dirstr_desc *)dirp;
+
+    if (!PTR_IN_ARRAY(opendirs, dirstr, MAX_OPEN_DIRS) || !dirstr->osdirp)
+        dirstr = NULL;
+    else if (dirstr->mounted)
+        return dirstr;
+
+    errno = dirstr ? ENXIO : EBADF;
+    DEBUGF("dir #%d: %s\n", (int)(dirstr - opendirs), strerror(errno));
+    return NULL;
+}
+
+static int close_dirstr(struct dirstr_desc *dirstr)
+{
+    OS_DIR_T *osdirp = dirstr->osdirp;
+
+    dirstr->mounted = false;
+
+#ifdef USE_OSDIRNAME
+    free(dirstr->osdirname);
+#endif
+    if (dirstr->osfd_opened)
+    {
+        os_close(dirstr->osfd);
+        dirstr->osfd_opened = false;
+    }
+
+    int rc = os_closedir(osdirp);
+    dirstr->osdirp = NULL;
+
+    return rc;
+}
+
+#ifdef HAVE_MULTIVOLUME
+static int readdir_volume_inner(struct dirstr_desc *dirstr,
+                                struct sim_dirent *entry)
+{
+    /* Volumes (secondary file systems) get inserted into the system root
+     * directory. If the path specified volume 0, enumeration will not
+     * include other volumes, but just its own files and directories.
+     *
+     * Fake special directories, which don't really exist, that will get
+     * redirected upon opendir()
+     */
+    while (++dirstr->volumecounter < NUM_VOLUMES)
+    {
+        /* on the system root */
+        if (!volume_present(dirstr->volumecounter))
+            continue;
+
+        get_volume_name(dirstr->volumecounter, entry->d_name);
+        return 1;
+    }
+
+    /* do normal directory entry fetching */
+    return 0;
+}
+#endif /* HAVE_MULTIVOLUME */
+
+static inline int readdir_volume(struct dirstr_desc *dirstr,
+                                 struct sim_dirent *entry)
+{
+#ifdef HAVE_MULTIVOLUME
+    if (dirstr->volumecounter < NUM_VOLUMES)
+        return readdir_volume_inner(dirstr, entry);
+#endif /* HAVE_MULTIVOLUME */
+
+    /* do normal directory entry fetching */
+    return 0;
+    (void)dirstr; (void)entry;
+}
+
+
+/** Internal functions **/
+
+#ifdef HAVE_MULTIDRIVE
+/**
+ * Handle drive extraction by pretending the files' volumes no longer exist
+ * and invalidating their I/O for the remainder of their lifetimes as would
+ * happen on a native target
+ */
+void sim_ext_extracted(int drive)
+{
+    for (unsigned int i = 0; i < MAX_OPEN_FILES; i++)
+    {
+        struct filestr_desc *filestr = &openfiles[i];
+        if (filestr->osfd >= 0 && volume_drive(filestr->volume) == drive)
+            filestr->mounted = false;
+    }
+
+    for (unsigned int i = 0; i < MAX_OPEN_DIRS; i++)
+    {
+        struct dirstr_desc *dirstr = &opendirs[i];
+        if (dirstr->osdirp && volume_drive(dirstr->volume) == drive)
+            dirstr->mounted = false;
+    }
+
+    (void)drive;
+}
+#endif /* HAVE_MULTIDRIVE */
+
+/**
+ * Provides target-like path parsing behavior with single and multiple volumes
+ * while performing minimal transforming of the input.
+ *
+ * Paths are sandboxed to the simulated namespace:
+ *   e.g. "{simdir}/foo/../../../../bar" becomes "{simdir}/foo/../bar"
+ */
+int sim_get_os_path(char *buffer, const char *path, size_t bufsize)
+{
+    #define ADVBUF(amt) \
+        ({ buffer += (amt); bufsize -= (amt); })
+
+    #define PPP_SHOWPATHS 0
+
+    if (!path_is_absolute(path))
+    {
+        DEBUGF("ERROR: path is not absolute: \"%s\"\n", path);
+        errno = ENOENT;
+        return -1;
+    }
+
+#if PPP_SHOWPATHS
+    const char *const buffer0 = buffer;
+    DEBUGF("PPP (pre): \"%s\"\n", path);
+#endif
+
+    /* Prepend sim root */
+    size_t size = strlcpy(buffer, sim_root_dir, bufsize);
+    if (size >= bufsize)
+    {
+        errno = ENAMETOOLONG;
+        return -1;
+    }
+    ADVBUF(size);
+
+#ifdef HAVE_MULTIVOLUME
+    /* Track the last valid volume spec encountered */
+    int volume = -1;
+    bool sysroot = true;
+
+    /* Basename of sim dir to switch back to simdisk from ext */
+    #define DIRBASE_FMT  ".." PATH_SEPSTR "%s"
+    ssize_t dirbase_len = 0;
+    char dirbase[size + 3 + 1];
+
+    /* Basename of ext directory to switch to alternate volume */
+    #define SIMEXT_FMT   ".." PATH_SEPSTR "simext%d"
+    char extbuf[sizeof (SIMEXT_FMT) + 20 + 1];
+#endif /* HAVE_MULTIVOLUME */
+
+    int level = 0;
+    bool done = false;
+    while (!done)
+    {
+        const char *p;
+        ssize_t len = parse_path_component(&path, &p);
+
+
+        switch (len)
+        {
+        case 0:
+            done = true;
+            if (path[-1] != PATH_SEPCH)
+                continue;
+
+            /* Path ends with a separator; preserve that */
+            p = &path[-1];
+            len = 1;
+            break;
+
+        case 1:
+        case 2:
+            if (p[0] == '.')
+            {
+                if (len == 1)
+                    break;
+
+                if (p[1] == '.')
+                    goto is_dot_dot;
+            }
+
+        default:
+            level++;
+
+        #ifdef HAVE_MULTIVOLUME
+            if (level != 1)
+                break; /* Volume spec only valid @ root level */
+
+            const char *next;
+            volume = path_strip_volume(p, &next, true);
+
+            if (next > p)
+            {
+            #ifdef HAVE_MULTIDRIVE
+                /* Feign failure if the volume isn't "mounted" */
+                if (!volume_present(volume))
+                {
+                    errno = ENXIO;
+                    return -1;
+                }
+            #endif /* HAVE_MULTIDRIVE */
+
+                sysroot = false;
+
+                if (volume == 0)
+                    continue;
+
+                p = extbuf;
+                len = snprintf(extbuf, sizeof (extbuf), SIMEXT_FMT, volume);
+            }
+        #endif /* HAVE_MULTIVOLUME */
+            break;
+
+        is_dot_dot:
+            if (level <= 0)
+                continue; /* Can't go above root; erase */
+
+            level--;
+
+        #ifdef HAVE_MULTIVOLUME
+            if (level == 0)
+            {
+                int v = volume;
+                bool sr = sysroot;
+                volume = -1;
+                sysroot = true;
+
+                if (v <= 0)
+                {
+                    if (sr)
+                        break;
+
+                    continue;
+                }
+
+                /* Going up from a volume root and back down to the sys root */
+                if (dirbase_len == 0)
+                {
+                    /* Get the main simdisk directory so it can be reentered */
+                    char tmpbuf[sizeof (dirbase)];
+                #ifdef WIN32
+                    path_correct_separators(tmpbuf, sim_root_dir);
+                    path_strip_drive(tmpbuf, &p, false);
+                #else
+                    p = tmpbuf;
+                    strcpy(tmpbuf, sim_root_dir);
+                #endif
+                    size = path_basename(p, &p);
+                    ((char *)p)[size] = '\0';
+
+                    if (size == 0 || is_dotdir_name(p))
+                    {
+                        /* This is nonsense and won't work */
+                        DEBUGF("ERROR: sim root dir basname is dotdir or"
+                               " empty: \"%s\"\n", sim_root_dir);
+                        errno = ENOENT;
+                        return -1;
+                    }
+
+                    dirbase_len = snprintf(dirbase, sizeof (dirbase),
+                                           DIRBASE_FMT, p);
+                }
+
+                p = dirbase;
+                len = dirbase_len;
+                break;
+            }
+        #endif /* HAVE_MULTIVOLUME */
+            break;
+        } /* end switch */
+
+        char compname[len + 1];
+        strmemcpy(compname, p, len);
+
+        size = path_append(buffer, PA_SEP_HARD, compname, bufsize);
+        if (size >= bufsize)
+        {
+            errno = ENAMETOOLONG;
+            return -1;
+        }
+        ADVBUF(size);
+    }
+
+#if PPP_SHOWPATHS
+    DEBUGF("PPP (post): \"%s\"" IF_MV(" vol:%d") "\n",
+           buffer0 IF_MV(, volume));
+#endif
+
+    return IF_MV(volume) +1;
+}
+
+
+/** File functions **/
+
+int sim_open(const char *path, int oflag, ...)
+{
+    int fildes;
+    struct filestr_desc *filestr = alloc_filestr(&fildes);
+    if (!filestr)
+    {
+        errno = EMFILE;
+        return -1;
+    }
+
+    char ospath[SIM_TMPBUF_MAX_PATH];
+    int pprc = sim_get_os_path(ospath, path, sizeof (ospath));
+    if (pprc < 0)
+        return -2;
+
+    filestr->osfd = os_open(ospath, oflag | O_BINARY __OPEN_MODE_ARG);
+    if (filestr->osfd < 0)
+        return -3;
+
+#ifdef HAVE_MULTIVOLUME
+    filestr->volume  = MAX(pprc - 1, 0);
+#endif
+    filestr->mounted = true;
+    return fildes;
+}
+
+int sim_creat(const char *path, mode_t mode)
+{
+    return sim_open(path, O_WRONLY|O_CREAT|O_TRUNC, mode);
+}
+
+int sim_close(int fildes)
+{
+    struct filestr_desc *filestr = &openfiles[fildes];
+    if ((unsigned int)fildes >= MAX_OPEN_FILES || filestr->osfd < 0)
+    {
+        errno = EBADF;
+        return -1;
+    }
+
+    int osfd = filestr->osfd;
+    filestr->osfd = -1;
+    return os_close(osfd);
+}
+
+int sim_ftruncate(int fildes, off_t length)
+{
+    struct filestr_desc *filestr = get_filestr(fildes);
+    if (!filestr)
+        return -1;
+
+    off_t size = os_filesize(filestr->osfd);
+    if (size < 0)
+        return -1;
+
+    if (length >= size)
+        return 0;
+
+    int rc = os_ftruncate(filestr->osfd, length);
+
+#ifdef HAVE_DIRCACHE
+    if (rc >= 0)
+        dircache_ftruncate(xxxxxx);
+#endif
+
+    return rc;
+}
+
+int sim_fsync(int fildes)
+{
+    struct filestr_desc *filestr = get_filestr(fildes);
+    if (!filestr)
+        return -1;
+
+    int rc = os_fsync(filestr->osfd);
+
+#ifdef HAVE_DIRCACHE
+    if (rc >= 0)
+        dircache_fsync(xxxxxx);
+#endif
+
+    return rc;
+}
+
+off_t sim_lseek(int fildes, off_t offset, int whence)
+{
+    struct filestr_desc *filestr = get_filestr(fildes);
+    if (!filestr)
+        return -1;
+
+    return os_lseek(filestr->osfd, offset, whence);
+}
+
+ssize_t sim_read(int fildes, void *buf, size_t nbyte)
+{
+    struct filestr_desc *filestr = get_filestr(fildes);
+    if (!filestr)
+        return -1;
+
+    return os_read(filestr->osfd, buf, nbyte);
+}
+
+ssize_t sim_write(int fildes, const void *buf, size_t nbyte)
+{
+    struct filestr_desc *filestr = get_filestr(fildes);
+    if (!filestr)
+        return -1;
+
+    return os_write(filestr->osfd, buf, nbyte);
+}
+
+int sim_remove(const char *path)
+{
+    char ospath[SIM_TMPBUF_MAX_PATH];
+    if (sim_get_os_path(ospath, path, sizeof (ospath)) < 0)
+        return -1;
+
+    int rc = os_remove(ospath);
+
+#ifdef HAVE_DIRCACHE
+    if (rc >= 0)
+        dircache_remove(xxxxxx);
+#endif
+
+    return rc;
+}
+
+int sim_rename(const char *old, const char *new)
+{
+    char osold[SIM_TMPBUF_MAX_PATH];
+    int pprc1 = sim_get_os_path(osold, old, sizeof (osold));
+    if (pprc1 < 0)
+        return -1;
+
+    char osnew[SIM_TMPBUF_MAX_PATH];
+    int pprc2 = sim_get_os_path(osnew, new, sizeof (osnew));
+    if (pprc2 < 0)
+        return -1;
+
+    if (MAX(pprc1 - 1, 0) != MAX(pprc2 - 1, 0))
+    {
+        /* Pretend they're different devices */
+        errno = EXDEV;
+        return -1;
+    }
+
+    int rc = os_rename(osold, osnew);
+
+#ifdef HAVE_DIRCACHE
+    if (rc >= 0)
+        dircache_rename(xxxxxx);
+#endif
+
+    return rc;
+}
+
+off_t sim_filesize(int fildes)
+{
+    struct filestr_desc *filestr = get_filestr(fildes);
+    if (!filestr)
+        return -1;
+
+    return os_filesize(filestr->osfd);
+}
+
+int sim_fsamefile(int fildes1, int fildes2)
+{
+    struct filestr_desc *filestr1 = get_filestr(fildes1);
+    if (!filestr1)
+        return -1;
+
+    struct filestr_desc *filestr2 = get_filestr(fildes2);
+    if (!filestr2)
+        return -1;
+
+    if (filestr1 == filestr2)
+        return 1;
+
+    return os_fsamefile(filestr1->osfd, filestr2->osfd);
+}
+
+int sim_relate(const char *path1, const char *path2)
+{
+    char ospath1[SIM_TMPBUF_MAX_PATH];
+    if (sim_get_os_path(ospath1, path1, sizeof (ospath1)) < 0)
+        return -1;
+
+    char ospath2[SIM_TMPBUF_MAX_PATH];
+    if (sim_get_os_path(ospath2, path2, sizeof (ospath2)) < 0)
+        return -1;
+
+    return os_relate(ospath1, ospath2);
+}
+
+bool sim_file_exists(const char *path)
+{
+    char ospath[SIM_TMPBUF_MAX_PATH];
+    if (sim_get_os_path(ospath, path, sizeof (ospath)) < 0)
+        return false;
+
+    return os_file_exists(ospath);
+}
+
+
+/** Directory functions **/
+DIR * sim_opendir(const char *dirname)
+{
+    struct dirstr_desc *dirstr = alloc_dirstr();
+    if (!dirstr)
+    {
+        errno = EMFILE;
+        return NULL;
+    }
+
+    char osdirname[SIM_TMPBUF_MAX_PATH];
+    int pprc = sim_get_os_path(osdirname, dirname, sizeof (osdirname));
+    if (pprc < 0)
+        return NULL;
+
+    int rc = os_opendir_and_fd(osdirname, &dirstr->osdirp, &dirstr->osfd);
+    if (rc < 0)
+        return NULL;
+
+    dirstr->osfd_opened = rc > 0;
+
+#ifdef USE_OSDIRNAME
+    dirstr->osdirname = strdup(osdirname);
+    if (!dirstr->osdirname)
+    {
+        close_dirstr(dirstr);
+        return NULL;
+    }
+#endif
+
+    dirstr->entry.d_name[0] = 0; /* Mark as invalid */
+#ifdef HAVE_MULTIVOLUME
+    dirstr->volume = MAX(pprc - 1, 0);
+    dirstr->volumecounter = pprc == 0 ? 0 : INT_MAX;
+#endif
+    dirstr->mounted = true;
+    return (DIR *)dirstr; /* A-Okay */
+}
+
+int sim_closedir(DIR *dirp)
+{
+    struct dirstr_desc *dirstr = (struct dirstr_desc *)dirp;
+    if (!PTR_IN_ARRAY(opendirs, dirstr, MAX_OPEN_DIRS) || !dirstr->osdirp)
+    {
+        errno = EBADF;
+        return -1;
+    }
+
+    return close_dirstr(dirstr);
+}
+
+struct sim_dirent * sim_readdir(DIR *dirp)
+{
+    struct dirstr_desc *dirstr = get_dirstr(dirp);
+    if (!dirstr)
+        return NULL;
+
+    struct sim_dirent *entry = &dirstr->entry;
+    entry->info.osdirent = NULL;
+
+    if (readdir_volume(dirstr, entry))
+        return entry;
+  
+    OS_DIRENT_T *osdirent = os_readdir(dirstr->osdirp);
+    if (!osdirent)
+        return NULL;
+
+    size_t size = sizeof (entry->d_name);
+    if (strlcpy_from_os(entry->d_name, osdirent->d_name, size) >= size)
+        FILE_ERROR_RETURN(ENAMETOOLONG, NULL);
+
+    entry->info.osdirent = osdirent;
+    return entry;
+}
+
+int sim_mkdir(const char *path)
+{
+    char ospath[SIM_TMPBUF_MAX_PATH];
+    if (sim_get_os_path(ospath, path, sizeof (ospath)) < 0)
+        return -1;
+
+    int rc = os_mkdir(ospath __MKDIR_MODE_ARG);
+
+#ifdef HAVE_DIRCACHE
+    if (rc >= 0)
+        dircache_mkdir(xxxxxx);
+#endif
+
+    return rc;
+}
+
+int sim_rmdir(const char *path)
+{
+    char ospath[SIM_TMPBUF_MAX_PATH];
+    if (sim_get_os_path(ospath, path, sizeof (ospath)) < 0)
+        return -1;
+
+    int rc = os_rmdir(ospath);
+
+#ifdef HAVE_DIRCACHE
+    if (rc >= 0)
+        dircache_rmdir(xxxxxx);
+#endif
+
+    return rc;
+}
+
+int sim_samedir(DIR *dirp1, DIR *dirp2)
+{
+    struct dirstr_desc *dirstr1 = get_dirstr(dirp1);
+    if (!dirstr1)
+        return -1;
+
+    struct dirstr_desc *dirstr2 = get_dirstr(dirp2);
+    if (!dirstr2)
+        return -1;
+
+    return os_fsamefile(dirstr1->osfd, dirstr2->osfd);
+}
+
+bool sim_dir_exists(const char *dirname)
+{
+    char osdirname[SIM_TMPBUF_MAX_PATH];
+    if (sim_get_os_path(osdirname, dirname, sizeof (osdirname)) < 0)
+        return false;
+
+    OS_DIR_T *dirp = os_opendir(osdirname);
+    if (!dirp)
+        return false;
+
+    os_closedir(dirp);
+    return true;
+}
+
+struct dirinfo dir_get_info(DIR *dirp, struct sim_dirent *entry)
+{
+    int rc;
+    struct dirstr_desc *dirstr = get_dirstr(dirp);
+    if (!dirstr)
+        FILE_ERROR(ERRNO, RC);
+
+    if (entry->d_name[0] == 0)
+        FILE_ERROR(ENOENT, RC);
+
+    OS_DIRENT_T *osdirent = entry->info.osdirent;
+    if (osdirent == NULL)
+        return (struct dirinfo){ .attribute = ATTR_MOUNT_POINT };
+
+    struct dirinfo info;
+    info.attribute = 0;
+
+    OS_STAT_T s;
+
+#ifdef os_fstatat
+    if (os_fstatat(dirstr->osfd, entry->d_name, &s, 0))
+#else /* no fstatat; build file name for stat() */
+    char statpath[SIM_TMPBUF_MAX_PATH];
+    if (path_append(statpath, dirstr->osdirname, entry->d_name,
+                    sizeof (statpath)) >= sizeof (statpath))
+    {
+        FILE_ERROR(ENAMETOOLONG, RC);
+    }
+
+    if (os_stat(statpath, &s)) /* get info */
+#endif /* os_fstatat */
+    {
+        /* File size larger than 2 GB? */
+    #ifdef EOVERFLOW
+        if (errno == EOVERFLOW)
+            DEBUGF("stat overflow for \"%s\"\n", entry->d_name);
+    #endif
+        FILE_ERROR(ERRNO, RC);
+    }
+
+    if (S_ISDIR(s.st_mode))
+        info.attribute |= ATTR_DIRECTORY;
+
+    info.size = s.st_size;
+
+    struct tm tm;
+    if (localtime_r(&s.st_mtime, &tm) == NULL)
+        FILE_ERROR(ERRNO, RC);
+
+    info.mtime = mktime(&tm);
+
+    return info;
+
+file_error:
+    return (struct dirinfo){ .size = 0 };
+}
+
+int os_volume_path(IF_MV(int volume, ) char *buffer, size_t bufsize)
+{
+    if (!buffer || !bufsize IF_MV( || !volume_present(volume) ))
+        return -1;
+
+    char tmpbuf[SIM_TMPBUF_MAX_PATH];
+    tmpbuf[0] = '\0';
+
+#ifdef HAVE_MULTIVOLUME
+    char volname[VOL_MAX_LEN + 1];
+    get_volume_name(volume, volname);
+
+    if (path_append(tmpbuf, PA_SEP_HARD, volname, sizeof (volname))
+            >= sizeof (volname))
+        return -1;
+#endif /* HAVE_MULTIVOLUME */
+
+    if (path_append(tmpbuf, PA_SEP_HARD, ".", sizeof (tmpbuf))
+        >= sizeof (tmpbuf))
+        return -1;
+
+    return sim_get_os_path(buffer, tmpbuf, bufsize);
+}