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Explain the work with pointers in the following case

Hallo All

I have the following problem:

A function (for example GetBits(var P: Pointer)) returns me a pointer to a
number of bits (how many I know from the function GetSize : LongInt).
All I need is to read the Bits from P twice: once as an array of Byte and
once as an array of LongInt. Who can explain me how can I get the 5th Byte
or the 3rd LongInt from the memory allocated for P.

Best wishes
Alexander

icampbe1

Declare an array of each type that you want as a pointer type.

TYPE
taByte = ARRAY [0..99] OF BYTE;
taLInt = ARRAY [0..99] OF LONGINT;

paByte = ^taByte;
paLInt = ^taLInt;

VAR
BArray: paByte;
IArray: paLInt;

You pass BArray or IArray in the call (or whatever you want) and then use the array index:

Something := BArray^[34]; {This assumes that BArray contains a valid pointer}

Hope this helps,

Ian C.

sassas081597

ASKER

I do not know at design time the length of the array of bits. It can be 2 bytes as well as 100000 bytes. It depends on the result of the function getSize: LongInt. May be that it returns a number that exceeds the maximum length of an array.

ASKER CERTIFIED SOLUTION

peter_vc

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sassas081597

ASKER

I think you are right - this code is accepted by compiler. May be you can explain me why the code

lp:=lp+SizeOf(LongInt)

does not work in this case - the compiler stops. I think we write the same code.