Commit e9fd416e authored by Eric Blake's avatar Eric Blake Committed by Paolo Bonzini
Browse files

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: default avatarEric Blake <eblake@redhat.com>
Message-Id: <1469129688-22848-4-git-send-email-eblake@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 7423f417

include/qemu/osdep.h

+5 −1
Original line number Diff line number Diff line
@@ -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