3ds: 3ds port sources. Second set of two.

This commit adds new files written exclusively for the 3ds port.

Additional comments:

1. Plugins works, but will be enabled in future commits.
2. The port has only been tested on the New 3DS.
3. Not all features of rockbox have been tested so there may be bugs or non-functional features.
4. There is a known issue where a random crash can occur when exiting the app.

Change-Id: I122d0bea9aa604e04fca45ba8287cf79e6110769

firmware/target/hosted/ctru/lib/sys_file.h

@@ -0,0 +1,129 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ * $Id$
+ *
+ * Copyright (C) 2025 by Mauricio G.
+ *
+ * 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.
+ *
+ ****************************************************************************/
+#ifndef _SYS_FILE_H
+#define _SYS_FILE_H
+
+#include "bfile.h"
+
+/* Include for file.h and dir.h because mkdir and friends may be here */
+#include <sys/stat.h>
+
+#define strlcpy_from_os strlcpy
+
+#define AtomicLoad(ptr) __atomic_load_n((u32*)(ptr), __ATOMIC_SEQ_CST)
+#define AtomicAdd(ptr, value) __atomic_add_fetch((u32*)(ptr), value, __ATOMIC_SEQ_CST)
+
+struct filestr_base {
+    Pager*      cache;            /* buffer IO implementation (cache) */
+    Handle      handle;           /* file handle */
+    u64         size;             /* file size */
+    int         flags;            /* stream flags */
+    char        path[MAX_PATH+1];
+
+    LightLock   mtx;              /* serialization for this stream */
+};
+
+static inline void filestr_lock(struct filestr_base *stream)
+{
+    LightLock_Lock(&stream->mtx);
+}
+
+static inline void filestr_unlock(struct filestr_base *stream)
+{
+    LightLock_Unlock(&stream->mtx);
+}
+
+/* stream lock doesn't have to be used if getting RW lock writer access */
+#define FILESTR_WRITER 0
+#define FILESTR_READER 1
+
+#define FILESTR_LOCK(type, stream) \
+    ({ if (FILESTR_##type) filestr_lock(stream); })
+
+#define FILESTR_UNLOCK(type, stream) \
+    ({ if (FILESTR_##type) filestr_unlock(stream); })
+
+/** Synchronization used throughout **/
+
+/* acquire the filesystem lock as READER */
+static inline void file_internal_lock_READER(void)
+{
+    extern sync_RWMutex file_internal_mrsw;
+    sync_RWMutexRLock(&file_internal_mrsw);
+}
+
+/* release the filesystem lock as READER */
+static inline void file_internal_unlock_READER(void)
+{
+    extern sync_RWMutex file_internal_mrsw;
+    sync_RWMutexRUnlock(&file_internal_mrsw);
+}
+
+/* acquire the filesystem lock as WRITER */
+static inline void file_internal_lock_WRITER(void)
+{
+    extern sync_RWMutex file_internal_mrsw;
+    sync_RWMutexLock(&file_internal_mrsw);
+}
+
+/* release the filesystem lock as WRITER */
+static inline void file_internal_unlock_WRITER(void)
+{
+    extern sync_RWMutex file_internal_mrsw;
+    sync_RWMutexUnlock(&file_internal_mrsw);
+}
+
+#define ERRNO 0 /* maintain errno value */
+#define _RC   0 /* maintain rc value */
+
+/* NOTES: if _errno is a non-constant expression, it must set an error
+ *        number and not return the ERRNO constant which will merely set
+ *        errno to zero, not preserve the current value; if you must set
+ *        errno to zero, set it explicitly, not in the macro
+ *
+ *        if _rc is constant-expression evaluation to 'RC', then rc will
+ *        NOT be altered; i.e. if you must set rc to zero, set it explicitly,
+ *        not in the macro
+ */
+
+#define FILE_SET_CODE(_name, _keepcode, _value) \
+    ({  __builtin_constant_p(_value) ?                             \
+            ({ if ((_value) != (_keepcode)) _name = (_value); }) : \
+            ({ _name = (_value); }); })
+
+/* set errno and rc and proceed to the "file_error:" label */
+#define FILE_ERROR(_errno, _rc) \
+    ({  FILE_SET_CODE(errno, ERRNO, (_errno)); \
+        FILE_SET_CODE(rc, _RC, (_rc));          \
+        goto file_error; })
+
+/* set errno and return a value at the point of invocation */
+#define FILE_ERROR_RETURN(_errno, _rc...) \
+    ({ FILE_SET_CODE(errno, ERRNO, _errno); \
+       return _rc; })
+
+/* set errno and return code, no branching */
+#define FILE_ERROR_SET(_errno, _rc) \
+    ({ FILE_SET_CODE(errno, ERRNO, (_errno)); \
+       FILE_SET_CODE(rc, _RC, (_rc)); })
+
+#endif /* _SYS_FILE_H */
+