If I Blockread(F,buffer,4) with buffer being an array of byte, Is there a routine in fpc/lazarus which will revers the bytes for me?

This is what I want:
longv:=buffer[0];
longv+=buffer[1] shl 8;
longv+=buffer[2] shl 16;
longv+=buffer[3] shl 24;

Is there a function which does this for me?

Yes. See LEtoN, BEtoN, NtoLE and NtoBE.

BlockRead(F, FooLongInt, 4);
FooLongInt := LEtoN(FooLongInt);

Regards,

Andrew

Great, thanks Andrew.

2008/12/21 Andrew Haines :

Is there any documentation on this?
would the following:

longv:=LEtoN(@buffer[5]);

be the same as:

longv:=buffer[5];
longv+=buffer[6] shl 8;
longv+=buffer[7] shl 16;
longv+=buffer[8] shl 24;

2008/12/21 Andrew Haines :

Is there any documentation on this? would the following: longv:=LEtoN(@buffer[5]);

longv:=LEtoN(PLongint(@buffer[5])^);

Mattias

Hi Mattias,

Is there an equivalent for

shortv:=buffer[5];
shortv+=buffer[6] shl 8;

Many thanks

Dave

2008/12/21 Mattias Gaertner :

shortv:=LEtoN(PSmallInt(@buffer[5])^);

Mattias

Dave Coventry wrote

Is there any documentation on this?

http://www.freepascal.org/docs-html/rtl/system/index-5.html

No, it's better. It only performs a conversion from Little Endian to current encoding. So it will just copy the contents if your software is running in a little endian processor or do the adequate conversion if your software is running in a big endian processor.

Wow.

If I can push a little more: Can I read in an eight-byte IEEE double using the same trick?

2008/12/21 Felipe Monteiro de Carvalho :

Dave Coventry wrote

Wow. If I can push a little more: Can I read in an eight-byte IEEE double using the same trick?

The example below is not complete, you need to cast.

MyDouble:=LEtoN(PDouble(@buffer[5])^);

Use codejumping (find declaration) on LEtoN to see what variants exist.

Marc

AFAIK LEToN does not exist for double.
You have to write one.

Mattias

2008/12/22 Marc Weustink :

Thanks Marc, I hadn't thought of doing that...

Thanks to all the guys who have given me help on this; I wasn't sure that this list would be the best place to ask, but I was all googled out.

Ok, then I've only looked at it and didn't implement.

Marc