finding string data in byte buffer array

[rsballard]

I have a binary file that is a a bunch of consequtive
type x = record
header: array[1..256] of byte;
data: array[1..10000] of single;
end

The spec calls for a text string of data to appear at the same location of the header in each of these records. We'll it doesn't. It may move around a little or even sometimes the first of the string is missed and only partial data is written to the header.

I need to search for the head of the wanted string, allowing it to move 10-20 bytes or so and retrieve the index into the array for the head of the string. If it's not found within some reasonable range, return -1.

I can't make anything work. I need something like the PosEx function that will find a substring in a byte array.

Any help?

Thanks
Bob

 

[LorenPechtel]

SetLength(TestString, DesiredScanLength);
Move(InstanceOfX, TestString[1], DesiredScanLength);
Hit := Pos(SearchKey, TestString);

 

[towerbase]

The function that you require is StrPos which will locate a substring in a byte array. The function will return a pointer to the substring if it finds it otherwise it returns nil.

You will need to do convert the returned pointer to a numeric value.

For example, using your definition of the X record.

function FindSubStringInX ( RecX: X; target: string ): integer;
var
  ptr: pchar;
begin
  ptr := StrPos ( @RecX.header, target );
  if ptr = nil then
    result := -1
  else
    result :=  ptr - @RecX.header + 1;  // +1 because array is [1..256]
end;

 

[rsballard]

Thanks, gents. Sometimes I just need to discuss things to make the mental connection with my problem.

Bob