From a2bca0df04e000cd90227e651c9501043e36115f Mon Sep 17 00:00:00 2001
From: Stephen Heumann <stephenheumann@gmail.com>
Date: Wed, 13 Jul 2022 18:34:29 -0500
Subject: [PATCH] Implement O_APPEND mode.

This was documented as supported, but not actually implemented.
---
 fcntl.asm | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/fcntl.asm b/fcntl.asm
index 6d0750b..2a4186d 100644
--- a/fcntl.asm
+++ b/fcntl.asm
@@ -800,6 +800,7 @@ nbuff    equ   3                        new buffer pointer
          lda   files,X
          beq   lb0
          sta   wrRefnum
+         sta   smRefnum
          stx   filds
          lda   files+2,X                make sure the file is open for writing
          and   #O_WRONLY+O_RDWR
@@ -851,7 +852,12 @@ lb0e     sta   [nbuff]
          long  M
 lb0f     move4 nbuff,wrDataBuffer         set the data buffer start
 
-lb0g     OSWrite wrRec                  write the bytes
+lb0g     ldx   filds                    if the file is in O_APPEND mode then
+         lda   files+2,X
+         and   #O_APPEND
+         beq   lb0h
+         OSSet_Mark smRec                 set mark to EOF
+lb0h     OSWrite wrRec                  write the bytes
          bcc   lb1                      if an error occurred then
          lda   #EIO                       errno = EIO
          sta   >errno
@@ -875,4 +881,9 @@ wrRefnum ds    2
 wrDataBuffer ds 4
 wrRequestCount ds 4
 wrTransferCount ds 4
+
+smRec    dc    i'3'                     SetMark record
+smRefnum ds    2
+smBase   dc    i'1'                     EOF-displacement mode
+smDisplacement dc i4'0'                 displacement = 0
          end