From aad17a6f057dc57424c010c0d832e1f49592f044 Mon Sep 17 00:00:00 2001
From: Greg King <gregdk@users.sf.net>
Date: Thu, 29 Oct 2020 17:54:56 -0400
Subject: [PATCH] Made two GEOS directory functions return NULL if they can't
 give a valid entry.

---
 doc/geos.sgml                            | 19 ++++++++++---------
 libsrc/geos-common/file/get1stdirentry.s | 12 ++++++------
 libsrc/geos-common/file/getnxtdirentry.s | 14 +++++++-------
 3 files changed, 23 insertions(+), 22 deletions(-)

diff --git a/doc/geos.sgml b/doc/geos.sgml
index a10ade5d5..11ff9c534 100644
--- a/doc/geos.sgml
+++ b/doc/geos.sgml
@@ -858,20 +858,21 @@ The functions described here are common for SEQ and VLIR structures.
 <p>
 <tt/struct filehandle *GetNxtDirEntry (void)/
 <p>
-These two functions are best suited for scanning the whole directory for particular files. Note that
-the returned filehandles describe all file slots in the directory - even those with deleted files.
-The return value can be obtained by casting both sides to <tt/unsigned/ - as in the <tt/SetNextFree/
-function or read directly after a call to those two functions from <tt/r5/. The current sector number
-is in <tt/r1/ and the sector data itself is in <tt/diskBlkBuf/.
+Those two functions are best suited for scanning the whole directory for particular files. Note that
+the returned filehandles describe all file slots in the directory -- even those with deleted files.
+The return value is <tt/NULL/ if there are no more slots, or if there was a disk error.  The
+<tt/_oserror/ variable is non-zero if it was a disk error (see <tt>geos/gdisk.h</tt>).  The current
+directory track and sector numbers are in <tt/r1L/ and <tt/r1H/.  The sector data itself is in
+<tt/diskBlkBuf/.
 
 <sect3>FindFile
 <p>
 <tt/char FindFile (char *fName)/
 <p>
-This function scans the whole directory for the given filename. It returns either 0 (success) or 5
-(FILE_NOT_FOUND, defined in <tt/gdisk.h/) or any other fatal disk read error. After a successful
-<tt/FindFile/ you will have <tt/struct filehandle/ at <tt/dirEntryBuf/ filled with the file's data and
-other registers set as described in <tt/GetNxtDirEntry/.
+This function scans the whole directory for the given filename. It returns either 0 (success), 5
+(FILE_NOT_FOUND, defined in <tt>geos/gdisk.h</tt>), or any other fatal disk read error. After a successful
+<tt/FindFile()/, you will have <tt/struct filehandle/ at <tt/dirEntryBuf/ filled with the file's data, and
+other registers set as described in <tt/GetNxtDirEntry()/.
 
 <sect3>FindFTypes
 <p>
diff --git a/libsrc/geos-common/file/get1stdirentry.s b/libsrc/geos-common/file/get1stdirentry.s
index 381a35c6d..f0ad59388 100644
--- a/libsrc/geos-common/file/get1stdirentry.s
+++ b/libsrc/geos-common/file/get1stdirentry.s
@@ -1,7 +1,7 @@
 ;
-; Maciej 'YTM/Alliance' Witkowiak
+; 1999-10-26, Maciej 'YTM/Alliance' Witkowiak
+; 2020-10-29, Greg King
 ;
-; 26.10.99
 
 ; struct filehandle* Get1stDirEntry (void);
 
@@ -15,9 +15,9 @@ _Get1stDirEntry:
         jsr Get1stDirEntry
         stx __oserror
         txa
-        beq L0                  ; error?
-        jmp return0             ; return NULL
-
-L0:     lda r5L
+        bne L1                  ; jump if disk error
+        lda r5L
         ldx r5H
         rts
+
+L1:     jmp return0             ; return NULL if not valid entry
diff --git a/libsrc/geos-common/file/getnxtdirentry.s b/libsrc/geos-common/file/getnxtdirentry.s
index 16a31edcf..e8ccbf3a2 100644
--- a/libsrc/geos-common/file/getnxtdirentry.s
+++ b/libsrc/geos-common/file/getnxtdirentry.s
@@ -1,7 +1,7 @@
 ;
-; Maciej 'YTM/Alliance' Witkowiak
+; 1999-10-26, Maciej 'YTM/Alliance' Witkowiak
+; 2020-10-29, Greg King
 ;
-; 26.10.99
 
 ; struct filehandle* GetNxtDirEntry (void);
 
@@ -15,11 +15,11 @@ _GetNxtDirEntry:
         jsr GetNxtDirEntry
         stx __oserror
         txa
-        beq L0                  ; error?
+        bne L1                  ; jump if disk error
         tya
-        beq L0                  ; end of dir?
-        jmp return0             ; return NULL
-
-L0:     lda r5L
+        bne L1                  ; jump when no more entries
+        lda r5L
         ldx r5H
         rts
+
+L1:     jmp return0             ; return NULL if not valid entry