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FUNCTION D1h
-
Reduce
File
AX
BX
CX
DX
XXXXXXXX
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Entry:
AH
=
D1h
(function
code)
AL
= Method
BX =
File
handle
CX
=
Number
of
bytes
to
delete
SP;
BP:
SI:
Dl:
IP:
FLG
CS
DS
SS
ES
Exit;
AX
=
Error
code
CX
= Number
of
bytes deleted
Function
D1h
is
used
to
remove
a block
of
data from
a
file
and cause
the
file
to
shrink
by
the
amount
deleted.
On
entry
to
the
function,
the
handle
of
a
currently
opened
file
is
passed
in
BX,
the
number
of
bytes
to
delete
are
specified
in
CX, and
the deletion
method
is
specified
in
AL.
The
allowed
deletion
methods
are:
Method
Description
1
2
Delete
the specified
number
of
bytes
at
the
beginning
of
the
file.
Delete the
specified
number
of
bytes beginning
at
the current position
Delete the
specified
number
of
bytes
at
the
end
of
the
file.
On
return
from the
function,
the carry
flag
will
be
set
if
an
error
occurred,
and
the
error status
code
will
be
in
AX.
If
no
error
occurred, the carry
flag
will
be
reset
and
the actual
number
of
bytes deleted
from
the
file
will
be
in
CX.
If
an
attempt
was made
to
delete past the
end
of
the
file
then the
number
returned
in
AX
will
be
smaller than the
requested amount.
(This
is
not
considered
an
error
by
HH
O/S.)
Error
Returns:
52
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