r6.1.0:lfds610_abstraction_increment
Source Files
/liblfds610/src/lfds610_abstraction/lfds610_abstraction_increment.c /liblfds610/src/liblfds610_internal.h
Prototype
static LFDS610_INLINE lfds610_atom_t lfds610_abstraction_increment( volatile lfds610_atom_t *value );
Parameters
volatile lfds610_atom_t *value
- Pointer to value to atomically increment.
Return Value
The post-increment value.
Notes
Some platforms (Windows) offer atomic increment functions. Some platforms (gcc) only offer atomic add functions. On these platforms, this function will be internally implemented as an atomic add of 1.
Examples
Under GCC, there is a function __sync_add_and_fetch, which has the following prototype;
type __sync_fetch_and_add( type *ptr, type value, ... );
Where type is any type natively supported by the compiler. This is a generalised add function, rather than an increment only function, but gcc provides no increment only function, so we use this function with an add of 1. By using the GCC platform independent atomic instruction, we can write a single function which will work for everyone using GCC.
As such, the implementation of lfds610_abstraction_increment() on GCC looks like this;
#if (__GNUC__ >= 4 && __GNUC_MINOR__ >= 1 && __GNUC_PATCHLEVEL__ >= 0)
/* TRD : any OS on any CPU with GCC 4.1.0 or better
GCC 4.1.0 introduced the __sync_*() atomic intrinsics
__GNUC__ / __GNUC_MINOR__ / __GNUC_PATCHLEVEL__ indicates GCC and which version
*/
static LFDS610_INLINE lfds610_atom_t lfds610_abstraction_increment( volatile lfds610_atom_t *value )
{
assert( value != NULL );
// TRD : no need for casting here, GCC has a __sync_add_and_fetch() for all native types
return( (lfds610_atom_t) __sync_add_and_fetch(value, 1) );
}
#endif