Re: [libvirt] [PATCH 1/3] util: add virendian.h macros

On 02/11/2013 07:07 PM, Eric Blake wrote: > We have several cases where we need to read endian-dependent > data regardless of host endianness; rather than open-coding > these call sites, it will be nicer to funnel things through > a macro. > > The virendian.h file can be expanded to add writer functions, > and/or 16-bit access patterns, if needed. Also, if we need > to turn things into a function to avoid multiple evaluations > of buf, that can be done later. But for now, a macro worked. >

> +# define virReadBufInt32LE(buf) \ > + ((uint32_t)(uint8_t)((buf)[0]) | \ > + ((uint32_t)(uint8_t)((buf)[1]) << 8) | \ > + ((uint32_t)(uint8_t)((buf)[2]) << 16) | \ > + ((uint32_t)(uint8_t)((buf)[3]) << 24)) > + > +#endif /* __VIR_ENDIAN_H__ */ Looking at byteswap.h.in I'm reminded of what I've seen in a previous job where we had lots of byteswapping to do. The macros will "isolate" each byte to move, eg: #define bswap_32(x) ((((x) & 0x000000FF) << 24) | \ (((x) & 0x0000FF00) << 8) | \ (((x) & 0x00FF0000) >> 8) | \ (((x) & 0xFF000000) >> 24)) Not sure if it's necessary in this case, but figured I'd ask.

ACK