Fix the NUL device so it returns 0 bytes for reads, independent of whether

cooked or raw mode is used. It was broken for raw mode. Fixes problem
with DJGPP sed (see
http://sourceforge.net/tracker/index.php?func=detail&aid=1429741&group_id=49784&atid=457447)


git-svn-id: https://svn.code.sf.net/p/freedos/svn/kernel/trunk@1306 6ac86273-5f31-0410-b378-82cca8765d1b

kernel/dosfns.c

@@ -263,7 +263,7 @@ long DosRWSft(int sft_idx, size_t n, void FAR * bp, int mode)
 
       /* Test for eof and exit                */
       /* immediately if it is                 */
-      if (!(s->sft_flags & SFT_FEOF) || (s->sft_flags & SFT_FNUL))
+      if (!(s->sft_flags & SFT_FEOF))
         return 0;
 
       if (s->sft_flags & SFT_FCONIN)

kernel/kernel.asm

@@ -223,6 +223,10 @@ _nul_intr:
                 push    es
                 push    bx
                 les     bx,[cs:_ReqPktPtr]            ;es:bx--> rqheadr
+                cmp     byte [es:bx+2],4    ;if read, set 0 read
+                jne     no_nul_read
+                mov     word [es:bx+12h],0
+no_nul_read:
                 or      word [es:bx+3],100h ;set "done" flag
                 pop     bx
                 pop     es