4D Doc Center : BLOB to real

4D v13.4

BLOB

BLOB to real


BLOB to real ( blob ; realFormat {; offset} ) -> Function result

Parameter	Type	Description
blob	BLOB	BLOB from which to get the Real value
realFormat	Longint	0=Native real format, 1=Extended real format, 2=Macintosh Double real format, 3=Windows Double real format
offset	Variable	Offset within the BLOB (expressed in bytes)
		New offset after reading
Function result	Real	Real value

Description

The BLOB to real command returns a Real value read from the BLOB blob.

The realFormat parameter fixes the internal format and byte ordering of the Real value to be read. You pass one of the following predefined constants provided by 4D:

Constant	Type	Value
Extended real format	Longint	1
Macintosh double real format	Longint	2
Native real format	Longint	0
PC double real format	Longint	3

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

If you specify the optional offset variable parameter, the Read value is read at the offset (starting from zero) within the BLOB. If you do not specify the optional offset variable parameter, the first 8 or 10 bytes of the BLOB are read.

Note: You should pass an offset value between 0 (zero) and the size of the BLOB minus 8 or 10. 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 Real values from a BLOB, starting at the offset 0x200:

 $vlOffset:=0x200

 For($viLoop;0;19)

    $vrValue:=BLOB to real(vxSomeBlob;PC byte ordering;$vlOffset)

  ` Do something with $vrValue

 End for