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osdep: provide ROUND_DOWN macro

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osdep.h provides a ROUND_UP macro to hide bitwise operations for the
purpose of rounding a number up to a power of two; add a ROUND_DOWN
macro that does the same with truncation towards zero.

While at it, change the formatting of some comments.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2021-06-16 15:18:20 +02:00
parent 01ef8185b8
commit c9797456f6
1 changed files with 22 additions and 6 deletions
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28
include/qemu/osdep.h
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@ -319,11 +319,16 @@ extern "C" {
})
#endif
/* Round number down to multiple */
/*
* Round number down to multiple. Safe when m is not a power of 2 (see
* ROUND_DOWN for a faster version when a power of 2 is guaranteed).
*/
#define QEMU_ALIGN_DOWN(n, m) ((n) / (m) * (m))
/* 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) */
/*
* 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 */
@ -340,11 +345,22 @@ extern "C" {
/* 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
/*
* Round number down to multiple. Requires that d be a power of 2 (see
* QEMU_ALIGN_UP for a safer but slower version on arbitrary
* numbers); works even if d is a smaller type than n. */
* numbers); works even if d is a smaller type than n.
*/
#ifndef ROUND_DOWN
#define ROUND_DOWN(n, d) ((n) & -(0 ? (n) : (d)))
#endif
/*
* 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); works even if d is a smaller type than n.
*/
#ifndef ROUND_UP
#define ROUND_UP(n, d) (((n) + (d) - 1) & -(0 ? (n) : (d)))
#define ROUND_UP(n, d) ROUND_DOWN((n) + (d) - 1, (d))
#endif
#ifndef DIV_ROUND_UP