…without having to load NLSFUNC

…coded comma (,)

Earlier fix was #242 (this got the
cluster value to use wrong).

Original problem recorded in #241

Reset disk scriptlet:

nasm -I ~/proj/lmacros/ ~/proj/bootimg/bootimg.asm \
  -D_PAYLOADFILE=::empty -o diskempt.img
cp -a ~/proj/kernel/bin/kernel.sys fdkernel.sys

Run dosemu2 with -I "floppy { device diskempt.img }"

After a test, run /sbin/dosfsck -n diskempt.img

The following Script for lDebug files are test cases:

=== testshrt.sld
e 200 "A:\test.dat" 0
f 300 l 100 26
a
 mov ah, 3C
 mov cx, 0
 mov dx, 200
 int 21
 xchg bx, ax
 mov ax, 4200
 mov cx, 1000
 mov dx, cx
 int 21
 mov dx, 300
 mov cx, 10
 mov ah, 3F
 int 21
 .
r v0 := aao
a
 mov ah, 40
 int 21
 int3
 int3
 jmp (v0)
 .

=== testfull.sld
e 200 "A:\test.dat" 0
f 400 l 400 38
a
 mov ah, 3C
 mov cx, 0
 mov dx, 200
 int 21
 xchg bx, ax
 mov ax, 4200
 mov cx, ((#1424 * #1024 - 1) >> 10)
 mov dx, ((#1424 * #1024 - 1) & FFFF)
 int 21
 mov ah, 40
 mov dx, 400
 mov cx, 1
 int 21
 mov ah, 68
 int 21
 mov ax, 4202
 mov cx, -1
 mov dx, -10
 int 21
 mov ah, 40
 mov dx, 400
 mov cx, 10
 int 21
 int3
 mov ah, 68
 int 21
 nop
 int3
 nop
 jmp 100
 .

=== testful2.sld
e 200 "A:\test.dat" 0
f 400 l 400 38
a
 mov ah, 3C
 mov cx, 0
 mov dx, 200
 int 21
 xchg bx, ax
 mov ax, 4200
 mov cx, ((#1424 * #1024 - #512 - 1) >> 10)
 mov dx, ((#1424 * #1024 - #512 - 1) & FFFF)
 int 21
 mov ah, 40
 mov dx, 400
 mov cx, 1
 int 21
 mov ah, 68
 int 21
 mov ax, 4202
 mov cx, -1
 mov dx, -10
 int 21
 mov ah, 40
 mov dx, 400
 mov cx, 10
 int 21
 int3
 mov ah, 68
 int 21
 nop
 int3
 nop
 jmp 100
 .

=== testful3.sld
e 200 "A:\test.dat" 0
f 400 l 400 38
a
 mov ah, 3C
 mov cx, 0
 mov dx, 200
 int 21
 xchg bx, ax
 mov ax, 4200
 mov cx, ((#1424 * #1024 - #512) >> 10)
 mov dx, ((#1424 * #1024 - #512) & FFFF)
 int 21
 mov ah, 40
 mov dx, 400
 mov cx, 0
 int 21
 mov ah, 68
 int 21
 mov ax, 4202
 mov cx, -1
 mov dx, -10
 int 21
 mov ah, 40
 mov dx, 400
 mov cx, 10
 int 21
 int3
 mov ah, 68
 int 21
 nop
 int3
 nop
 jmp 100
 .

===

Reset disk scriptlet:

nasm -I ~/proj/lmacros/ ~/proj/bootimg/bootimg.asm \
  -D_PAYLOADFILE=::empty -o diskempt.img
cp -a ~/proj/kernel/bin/kernel.sys fdkernel.sys

Run dosemu2 with -I "floppy { device diskempt.img }"

After a test, run /sbin/dosfsck -n diskempt.img

The following Script for lDebug is a test case:

=== testsect.sld
e 200 "A:\test.dat" 0
f 400 l 400 38
a
 mov ah, 3C
 mov cx, 0
 mov dx, 200
 int 21
 xchg bx, ax
 mov ax, 4200
 mov cx, (#1024 >> 10)
 mov dx, (#1024 & FFFF)
 int 21
 mov ah, 40
 mov dx, 400
 mov cx, 0
 int 21
 int3
 mov ah, 68
 int 21
 nop
 int3
 nop
 jmp 100
 .

===

The prior revision incorrectly corrupted the file size even if just
scanning the file, including for read. Move the code so it only runs
after the very spot that found it is writing, needed to append a new
cluster to the chain, and successfully did do that.

Script for lDebug file to test this error:

=== testtrun.sld
e 200 "A:\test.dat" 0
f 400 l 400 38
a
 mov ah, 3C
 mov cx, 0
 mov dx, 200
 int 21
 xchg bx, ax
 mov ax, 4200
 mov cx, (#10240 >> 10)
 mov dx, (#10240 & FFFF)
 int 21
 mov ah, 40
 mov dx, 400
 mov cx, 0
 int 21
 mov ah, 68
 int 21
 nop
 mov ax, 4200
 xor cx, cx
 xor dx, dx
 int 21
 mov dx, 800
 mov ah, 3F
 mov cx, 380
 int 21
 int3
 mov ah, 68
 int 21
 nop
 int3
 nop
 jmp 100
 .
===

Original issue: #241

Test cases as Script for lDebug files:

test$ cat testw1b.sld
e 200 "A:\test.dat" 0
f 300 l 400 26
a
 mov ah, 3C
 mov cx, 0
 mov dx, 200
 int 21
 xchg bx, ax
 mov dx, 300
 mov cx, 1
 mov ah, 40
 int 21
 mov ah, 68
 int 21
 int3
 int3
 jmp 100
 .

test$ cat testwp1b.sld
e 200 "A:\test.dat" 0
f 300 l 400 26
a
 mov ah, 3C
 mov cx, 0
 mov dx, 200
 int 21
 xchg bx, ax
 mov ax, 4200
 xor cx, cx
 mov dx, 200
 int 21
 mov dx, 300
 mov cx, 1
 mov ah, 40
 int 21
 mov ah, 68
 int 21
 int3
 int3
 jmp 100
 .

test$ cat testwpp1.sld
e 200 "A:\test.dat" 0
f 300 l 400 26
a
 mov ah, 3C
 mov cx, 0
 mov dx, 200
 int 21
 xchg bx, ax
 mov ax, 4200
 xor cx, cx
 mov dx, 201
 int 21
 mov dx, 300
 mov cx, 1
 mov ah, 40
 int 21
 mov ah, 68
 int 21
 int3
 int3
 jmp 100
 .

test$ cat testw1c.sld
e 200 "A:\test.dat" 0
f 300 l 400 26
a
 mov ah, 3C
 mov cx, 0
 mov dx, 200
 int 21
 xchg bx, ax
 mov dx, 300
 mov cx, 201
 mov ah, 40
 int 21
 mov ah, 68
 int 21
 int3
 int3
 jmp 100
 .

test$ cat testwp1c.sld
e 200 "A:\test.dat" 0
f 300 l 400 26
a
 mov ah, 3C
 mov cx, 0
 mov dx, 200
 int 21
 xchg bx, ax
 mov ax, 4200
 xor cx, cx
 mov dx, 200
 int 21
 mov dx, 300
 mov cx, 201
 mov ah, 40
 int 21
 mov ah, 68
 int 21
 int3
 int3
 jmp 100
 .

test$

The possibility of fragmentation due to this misbehaviour was mentioned
in #245 And it's also just slower to
allocate the unneeded cluster just to free it again truncating the file.