dosfns: Check share table before delete/rename

Delete and Rename should not be able to remove an open file,
so check share's open file table first. Behaviour is now identical
to MS-DOS 6.22.

Note: Uses a new subfunction of the FreeDOS share multiplex
      interrupt int2f/0x10a6 called is_file_open()

A similar patch was applied to FDPP at
https://github.com/dosemu2/fdpp/commit/691721f1

Fixes dosemu2 tests:
  test_fat_ds3_share_open_rename_fcb
  test_fat_ds3_share_open_rename_ds2
  test_fat_ds3_share_open_delete_ds2
  test_fat_ds3_share_open_delete_fcb

kernel/dosfns.c

@@ -86,6 +86,13 @@ extern int ASMPASCAL
                              unsigned long len, /* length (in bytes) of region to lock or unlock */
                              int unlock);       /* one to unlock; zero to lock */
 
+        /* DOS calls this to see if share already has the file marked as open.
+           Returns:
+             1 if open
+             0 if not */
+extern int ASMPASCAL
+            share_is_file_open(const char far * filename);
+
 /* /// End of additions for SHARE.  - Ron Cemer */
 
 STATIC int remote_lock_unlock(sft FAR *sftp,    /* SFT for file */
@@ -1214,6 +1221,9 @@ COUNT DosDelete(BYTE FAR * path, int attrib)
   if (result & IS_DEVICE)
     return DE_FILENOTFND;
 
+  if (IsShareInstalled(TRUE) && share_is_file_open(PriPathName))
+    return DE_ACCESS;
+
   return dos_delete(PriPathName, attrib);
 }
 
@@ -1226,6 +1236,9 @@ COUNT DosRenameTrue(BYTE * path1, BYTE * path2, int attrib)
   if (FP_OFF(current_ldt) == 0xFFFF || (current_ldt->cdsFlags & CDSNETWDRV))
     return network_redirector(REM_RENAME);
 
+  if (IsShareInstalled(TRUE) && share_is_file_open(path1))
+    return DE_ACCESS;
+
   return dos_rename(path1, path2, attrib);
 }
 

kernel/int2f.asm

@@ -342,6 +342,25 @@ SHARE_LOCK_UNLOCK:
 		mov	ax,0x10a4
 		jmp	short share_common
 
+;           DOS calls this to see if share already has the file marked as open.
+;           Returns:
+;             1 if open
+;             0 if not
+; STATIC WORD share_is_file_open(const char far *filename) /* pointer to fully qualified filename */
+		global SHARE_IS_FILE_OPEN
+SHARE_IS_FILE_OPEN:
+		mov	si, ds
+		mov	es, si		; save ds
+		pop	ax		; save return address
+		pop	si		; filename
+		pop	ds		; SEG filename
+		push	ax		; restore return address
+		mov	ax, 0x10a6
+		int	0x2f	     	; returns ax
+		mov	si, es		; restore ds
+		mov	ds, si
+		ret
+
 ; Int 2F Multipurpose Remote System Calls
 ;
 ; added by James Tabor jimtabor@infohwy.com

kernel/kernel.ld

@@ -114,6 +114,7 @@ SECTIONS
 		_share_close_file = SHARE_CLOSE_FILE;
 		_share_access_check = SHARE_ACCESS_CHECK;
 		_share_lock_unlock = SHARE_LOCK_UNLOCK;
+		_share_is_file_open = SHARE_IS_FILE_OPEN;
 		_call_nls = CALL_NLS;
 		_fl_reset = FL_RESET;
 		_fl_diskchanged = FL_DISKCHANGED;