4D Doc Center : BLOB to longint

4D v13.4

BLOB

BLOB to longint


BLOB to longint ( blob ; byteOrder {; offset} ) -> Function result

Parameter	Type	Description
blob	BLOB	BLOB from which to get the Long Integer value
byteOrder	Longint	0 = Native byte ordering, 1 = Macintosh byte ordering, 2 = PC byte ordering
offset	Variable	Offset within the BLOB (expressed in bytes)
		New offset after reading
Function result	Longint	4-byte Long Integer value

Description

The BLOB to longint command returns a 4-byte Long Integer value read from the BLOB blob.

The byteOrder parameter fixes the byte ordering of the 4-byte Long Integer value to be read. You pass one of the following predefined constants provided by 4D:

Constant	Type	Value
Macintosh byte ordering	Longint	1
Native byte ordering	Longint	0
PC byte ordering	Longint	2

Note regarding Platform Independence: If you exchange BLOBs between Macintosh and PC platforms, it is up to you to manage byte swapping issues while using this command.

If you specify the optional offset variable parameter, the 4-byte Long Integer is read at the offset (starting from zero) within the BLOB. If you do not specify the optional offset variable parameter, the first four bytes of the BLOB are read.

Note: You should pass an offset value between 0 (zero) and the size of the BLOB minus 4. If you do not do so, an error -111 is generated.

After the call, the variable is incremented by the number of bytes read. Therefore, you can reuse that same variable with another BLOB reading command to read another value.

Example

The following example reads 20 Long Integer values from a BLOB, starting at the offset 0x200:

 $vlOffset:=0x200

 For($viLoop;0;19)

    $vlValue:=BLOB to longint(vxSomeBlob;PC byte ordering;$vlOffset)

  ` Do something with $vlValue

 End for