mirror of
https://gitlab.uni-freiburg.de/opensourcevdi/spice-common
synced 2025-12-27 15:08:21 +00:00
74e50b57ae
Instead of assuming that the system can safely do unaligned access
to memory use packed structures to allow the compiler generate
best code possible.
A packed structure tells the compiler to not leave padding inside it
and that the structure can be unaligned so any field can be unaligned
having to generate proper access code based on architecture.
For instance ARM7 can use unaligned access but not for 64 bit
numbers (currently these accesses are emulated by Linux kernel
with obvious performance consequences).
This changes the current methods from:
#ifdef WORDS_BIGENDIAN
#define read_uint32(ptr) ((uint32_t)SPICE_BYTESWAP32(*((uint32_t *)(ptr))))
#define write_uint32(ptr, val) *(uint32_t *)(ptr) = SPICE_BYTESWAP32((uint32_t)val)
#else
#define read_uint32(ptr) (*((uint32_t *)(ptr)))
#define write_uint32(ptr, val) (*((uint32_t *)(ptr))) = val
#endif
to:
#include <spice/start-packed.h>
typedef struct SPICE_ATTR_PACKED {
uint32_t v;
} uint32_unaligned_t;
#include <spice/end-packed.h>
#ifdef WORDS_BIGENDIAN
#define read_uint32(ptr) ((uint32_t)SPICE_BYTESWAP32(((uint32_unaligned_t *)(ptr))->v))
#define write_uint32(ptr, val) ((uint32_unaligned_t *)(ptr))->v = SPICE_BYTESWAP32((uint32_t)val)
#else
#define read_uint32(ptr) (((uint32_unaligned_t *)(ptr))->v)
#define write_uint32(ptr, val) (((uint32_unaligned_t *)(ptr))->v) = val
#endif
Signed-off-by: Frediano Ziglio <fziglio@redhat.com>
Acked-by: Christophe Fergeau <cfergeau@redhat.com>
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| build-aux | ||
| common | ||
| docs | ||
| m4 | ||
| python_modules | ||
| tests | ||
| .gitmodules | ||
| autogen.sh | ||
| configure.ac | ||
| COPYING | ||
| git.mk | ||
| Makefile.am | ||
| spice1.proto | ||
| spice_codegen.py | ||
| spice.proto | ||