I have a function that I'm trying to pass an array to.

function FieldValueAsString(fsbuffer: array of Byte; fitype,fisize:
integer): string;

Calling the function:

setlength(fsbuffer,recordsize);
FS:=TFileStream.Create(fname, fmshareDenyWrite);
FS.Seek(seekpos,soFromBeginning);
FS.ReadBuffer(fsbuffer,recordsize);
dfstring:= FieldValueAsString(fsbuffer,fitype,fisize);

Generates the error "Project raised exception class SIGSEGV"

Hi Dave,

My first comment would be you must declare the input as a variable. Next, I probably would type the Array out as well before using it.

Type TByteBuffer=Array of Byte;
function FieldValueAsString(var fsbuffer:TByteBuffer; fitype,fisize:
integer): string;

Byte arrays should not generate an error. There may be a memory leak for instances where you pass them in as constant values. Because the Memory manager would need to free that memory as it is a dynamic array.

-Andy

Not sure, but I would try something like

FS.ReadBuffer(fsbuffer[0],recordsize);

The function is declared as
ReadBuffer(var Buffer; ....

So in reality a pointer to the variable is passed to the function. Your dyn-array is already a pointer. You are passing in a pointer to the internal pointer, and not to the bytes you allocated.

Martin

Hi Andy, thanks for the response.

The array was declared as
var fsbuffer: array of Byte;
I tried your suggestion and typed the array as
Type TByteBuffer=Array of Byte;
then declared the buffer
var fsbuffer: TByteBuffer;

I also declared the function using 'var' as you suggested

function FieldValueAsString(var fsbuffer: TByteBuffer; fitype,fisize:
integer): string;

But my app is still falling over at the same point.

2009/1/19 Andrew Brunner :

Thanks Martin, that works.

2009/1/19 Dave Coventry :

Ok,

But when reading or writing to the buffer you do need to reference the element in which you want to start writing/reading... In the case that entire buffer is to be written use [0].

You can't write the buffer itself as it's just a pointer...

Can you give more information about your function.

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ALEXIO CHAOS

Yahoo Messager

=================================

--- On Mon, 1/19/09, Dave Coventry wrote:

2009/1/20 Darmawan Sugiarto :

Can you give more information about your function.

Sure:

function FieldValueAsString(var fsbuffer: TByteBuffer;
fitype,marker,fisize: integer): string;
begin
  case fitype of
43,52,108:Result:=inttostr(LEtoN(PLongint(@fsbuffer[marker])^));
 50:Result:=inttostr(LEtoN(PSmallInt(@fsbuffer[marker])^));
end;
end;

It was failing before it got there, so I don't think the problem was with the function.

In any case, Martin's suggestion regarding calling the ReadBuffer function with the first element of the array rather than the pointer has worked...

Congratulation, so this case was closed

=============INTOSOFT============

ALEXIO CHAOS

Yahoo Messager

=================================

--- On Mon, 1/19/09, Dave Coventry wrote: