include/linux/math.h

Source file repositories/reference/linux-study-clean/include/linux/math.h

File Facts

System
Linux kernel
Corpus path
include/linux/math.h
Extension
.h
Size
6091 bytes
Lines
212
Domain
Core OS
Bucket
Core Kernel Interface
Inferred role
Core OS: implementation source
Status
source implementation candidate

Why This File Exists

Core operating-system implementation surface: boot, tasks, memory, VFS, syscall-facing interfaces, synchronization, credentials, and isolation.

Dependency Surface

Detected Declarations

Annotated Snippet

#ifndef _LINUX_MATH_H
#define _LINUX_MATH_H

#include <linux/types.h>
#include <asm/div64.h>
#include <uapi/linux/kernel.h>

/*
 * This looks more complex than it should be. But we need to
 * get the type for the ~ right in round_down (it needs to be
 * as wide as the result!), and we want to evaluate the macro
 * arguments just once each.
 */
#define __round_mask(x, y) ((__typeof__(x))((y)-1))

/**
 * round_up - round up to next specified power of 2
 * @x: the value to round
 * @y: multiple to round up to (must be a power of 2)
 *
 * Rounds @x up to next multiple of @y (which must be a power of 2).
 * To perform arbitrary rounding up, use roundup() below.
 */
#define round_up(x, y) ((((x)-1) | __round_mask(x, y))+1)

/**
 * round_down - round down to next specified power of 2
 * @x: the value to round
 * @y: multiple to round down to (must be a power of 2)
 *
 * Rounds @x down to next multiple of @y (which must be a power of 2).
 * To perform arbitrary rounding down, use rounddown() below.
 */
#define round_down(x, y) ((x) & ~__round_mask(x, y))

/**
 * DIV_ROUND_UP_POW2 - divide and round up
 * @n: numerator
 * @d: denominator (must be a power of 2)
 *
 * Divides @n by @d and rounds up to next multiple of @d (which must be a power
 * of 2). Avoids integer overflows that may occur with __KERNEL_DIV_ROUND_UP().
 * Performance is roughly equivalent to __KERNEL_DIV_ROUND_UP().
 */
#define DIV_ROUND_UP_POW2(n, d) \
	((n) / (d) + !!((n) & ((d) - 1)))

#define DIV_ROUND_UP __KERNEL_DIV_ROUND_UP

#define DIV_ROUND_DOWN_ULL(ll, d) \
	({ unsigned long long _tmp = (ll); do_div(_tmp, d); _tmp; })

#define DIV_ROUND_UP_ULL(ll, d) \
	DIV_ROUND_DOWN_ULL((unsigned long long)(ll) + (d) - 1, (d))

#if BITS_PER_LONG == 32
# define DIV_ROUND_UP_SECTOR_T(ll,d) DIV_ROUND_UP_ULL(ll, d)
#else
# define DIV_ROUND_UP_SECTOR_T(ll,d) DIV_ROUND_UP(ll,d)
#endif

/**
 * roundup - round up to the next specified multiple
 * @x: the value to up
 * @y: multiple to round up to
 *
 * Rounds @x up to next multiple of @y. If @y will always be a power
 * of 2, consider using the faster round_up().
 */
#define roundup(x, y) (					\
{							\
	typeof(y) __y = y;				\
	(((x) + (__y - 1)) / __y) * __y;		\
}							\
)
/**
 * rounddown - round down to next specified multiple
 * @x: the value to round
 * @y: multiple to round down to
 *
 * Rounds @x down to next multiple of @y. If @y will always be a power
 * of 2, consider using the faster round_down().
 */
#define rounddown(x, y) (				\
{							\
	typeof(x) __x = (x);				\
	__x - (__x % (y));				\
}							\
)

Annotation

Implementation Notes