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utils: add nl_has_capability() function

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Acked-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: Thomas Haller <thaller@redhat.com>
This commit is contained in:
Thomas Haller 2014-03-13 13:16:05 +01:00
parent a126d66b58
commit 68d6bd7f37
2 changed files with 51 additions and 0 deletions
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8
include/netlink/utils.h
View file

@ -79,6 +79,14 @@ extern void nl_new_line(struct nl_dump_params *);
extern void nl_dump(struct nl_dump_params *, const char *, ...);
extern void nl_dump_line(struct nl_dump_params *, const char *, ...);
enum {
NL_CAPABILITY_NONE,
__NL_CAPABILITY_MAX
#define NL_CAPABILITY_MAX (__NL_CAPABILITY_MAX - 1)
};
int nl_has_capability (int capability);
#ifdef __cplusplus
}
#endif

43
lib/utils.c
View file

@ -1111,6 +1111,49 @@ void dump_from_ops(struct nl_object *obj, struct nl_dump_params *params)
obj->ce_ops->oo_dump[type](obj, params);
}
/**
* Check for library capabilities
*
* @arg capability capability identifier
*
* Check whether the loaded libnl library supports a certain capability.
* This is useful so that applications can workaround known issues of
* libnl that are fixed in newer library versions, without
* having a hard dependency on the new version. It is also useful, for
* capabilities that cannot easily be detected using autoconf tests.
* The capabilities are integer constants with name NL_CAPABILITY_*.
*
* As this function is intended to detect capabilities at runtime,
* you might not want to depend during compile time on the NL_CAPABILITY_*
* names. Instead you can use their numeric values which are guaranteed not to
* change meaning.
*
* @return non zero if libnl supports a certain capability, 0 otherwise.
**/
int nl_has_capability (int capability)
{
static const uint8_t caps[ ( NL_CAPABILITY_MAX + 7 ) / 8 ] = {
#define _NL_ASSERT(expr) ( 0 * sizeof(struct { unsigned int x: ( (!!(expr)) ? 1 : -1 ); }) )
#define _NL_SETV(i, r, v) \
( _NL_ASSERT( (v) == 0 || (i) * 8 + (r) == (v) - 1 ) + \
( (v) == 0 ? 0 : (1 << (r)) ) )
#define _NL_SET(i, v0, v1, v2, v3, v4, v5, v6, v7) \
[(i)] = ( \
_NL_SETV((i), 0, (v0)) | _NL_SETV((i), 4, (v4)) | \
_NL_SETV((i), 1, (v1)) | _NL_SETV((i), 5, (v5)) | \
_NL_SETV((i), 2, (v2)) | _NL_SETV((i), 6, (v6)) | \
_NL_SETV((i), 3, (v3)) | _NL_SETV((i), 7, (v7)) )
#undef _NL_SET
#undef _NL_SETV
#undef _NL_ASSERT
};
if (capability <= 0 || capability > NL_CAPABILITY_MAX)
return 0;
capability--;
return (caps[capability / 8] & (1 << (capability % 8))) != 0;
}
/** @endcond */
/** @} */