On Fri, Aug 07, 2015 at 01:29:57PM +0100, Frediano Ziglio wrote: > This macro allow to define magic constants without using weird > memory tweacks. > This remove some possible warning from some compiler and > make code more optimized as compiler is able to compute the > constant. > > Signed-off-by: Frediano Ziglio <fziglio@xxxxxxxxxx> > --- > spice/controller_prot.h | 2 +- > spice/foreign_menu_prot.h | 2 +- > spice/macros.h | 6 ++++++ > spice/protocol.h | 2 +- > spice/qxl_dev.h | 4 ++-- > spice/stats.h | 2 +- > spice/vdi_dev.h | 2 +- > 7 files changed, 13 insertions(+), 7 deletions(-) > > diff --git a/spice/macros.h b/spice/macros.h > index 018ff32..4647ee3 100644 > --- a/spice/macros.h > +++ b/spice/macros.h > @@ -359,5 +359,11 @@ > # define SPICE_BYTESWAP64(val) (SPICE_BYTESWAP64_CONSTANT (val)) > #endif /* generic */ > > +#if SPICE_ENDIAN == SPICE_ENDIAN_LITTLE > +#define SPICE_MAGIC_CONST(s) ((uint32_t)(s[0]+s[1]*0x100u+s[2]*0x10000u+s[3]*0x1000000u)) > +#else > +#define SPICE_MAGIC_CONST(s) ((uint32_t)(s[3]+s[2]*0x100u+s[1]*0x10000u+s[0]*0x1000000u)) > +#endif > + If I'm not mistaken, we can keep the (*(const uint32_t*)"QXRO") method for little-endian (or are you avoiding -Wcast-align warnings at the same time)? This could potentially use SPICE_BYTESWAP32_CONSTANT (but I assume there is still this -Wcast-align warning to take care of?) What about SPICE_ENDIAN_PDP, I believe this is not going to be correct? (I would just error out at compile time if we find out the endianness is PDP). I'd favour << and | over +/* for what it's worth, and make sure we are operating on unsigned chars. Christophe
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