[fpc-pascal] Converting big-endian signed 16bits values to fpc integer

[Jonas Maebe]

On 16 Apr 2012, at 00:38, Giuliano Colla wrote:

> I'm dealing with a large number of data coming from an external device.
> They are big-endian 16 bits signed numbers, which must be converted to integer and to real to perform calculations.
> 
> Besides the obvious solutions of treating them as isolated bytes, multipying by 256 the highest, adding the lower, and oring wit $FFFF0000, or whatever sizeof(Integer) suggests if the result is bigger than 32767, is there a more efficient and elegant way to achieve the result?

Call BEtoN() on them (Big Endian to Native byte order). Note that this routine is overloaded for all integer sizes > 1, and that FPC extends the size of any number < 32/64 bits (depending on the architecture) to 32/64 bits when performing almost any operation on it. It's therefore probably the safest to call it as BEtoN(smallint(value)) to ensure that the correct overload is selected.


Jonas