On Wed, 4 May 2011, Kevin Bailey wrote:
On Wed, May 4, 2011 at 7:31 PM, Erik Petrich
<epetr...@ivorytower.norman.ok.us> wrote:
long_counter = (unsigned int)(char_counter[0] | (char_counter[1] << 8)) |
((unsigned long)(char_counter[2] | (char_counter[3] << 8)) << 16);
I hope the first (unsigned int) cast isn't necessary, because the
char_counter[1] << 8 would overflow if it wasn't implicitly an int.
Yes, char_counter[1] << 8 is implicitly an int. The cast is needed to
force it to be unsigned. Otherwise during conversion from (signed) int to
unsigned long the most significant bit of the int result will be copied to
all of the bits in the upper half of the long, which could then interfere
with the bytes from char_counter[2] and char_counter[3]. Converting from
unsigned int to unsigned long will force all the bits in the upper half of
the long to 0, so no interference. My original suggestion omitted this
cast and failed because I forgot to take this signed int to unsigned long
behaviour into account.
Erik
------------------------------------------------------------------------------
WhatsUp Gold - Download Free Network Management Software
The most intuitive, comprehensive, and cost-effective network
management toolset available today. Delivers lowest initial
acquisition cost and overall TCO of any competing solution.
http://p.sf.net/sfu/whatsupgold-sd
_______________________________________________
Sdcc-user mailing list
Sdcc-user@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/sdcc-user
