diff options
| author | Eric Blake <eblake@redhat.com> | 2016-07-21 13:34:47 -0600 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2016-08-03 18:44:56 +0200 |
| commit | e9fd416e66539ad43bbab018f346cb164136c099 (patch) | |
| tree | 1e5c85ddf147c6faecc151843a356b255f3ba2fb | |
| parent | 7423f417827146f956df820f172d0bf80a489495 (diff) | |
osdep: Document differences in rounding macros
Make it obvious which macros are safe in which situations.
Useful since QEMU_ALIGN_UP and ROUND_UP both purport to do
the same thing, but differ on whether the alignment must be
a power of 2.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1469129688-22848-4-git-send-email-eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
| -rw-r--r-- | include/qemu/osdep.h | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h index d7c111d169..9e9fa61546 100644 --- a/include/qemu/osdep.h +++ b/include/qemu/osdep.h @@ -158,7 +158,8 @@ extern int daemon(int, int); /* Round number down to multiple */ #define QEMU_ALIGN_DOWN(n, m) ((n) / (m) * (m)) -/* Round number up to multiple */ +/* Round number up to multiple. Safe when m is not a power of 2 (see + * ROUND_UP for a faster version when a power of 2 is guaranteed) */ #define QEMU_ALIGN_UP(n, m) QEMU_ALIGN_DOWN((n) + (m) - 1, (m)) /* Check if n is a multiple of m */ @@ -175,6 +176,9 @@ extern int daemon(int, int); /* Check if pointer p is n-bytes aligned */ #define QEMU_PTR_IS_ALIGNED(p, n) QEMU_IS_ALIGNED((uintptr_t)(p), (n)) +/* Round number up to multiple. Requires that d be a power of 2 (see + * QEMU_ALIGN_UP for a safer but slower version on arbitrary + * numbers) */ #ifndef ROUND_UP #define ROUND_UP(n,d) (((n) + (d) - 1) & -(d)) #endif |