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- /* SPDX-License-Identifier: GPL-2.0 */
- #ifndef _LINUX_MINMAX_H
- #define _LINUX_MINMAX_H
- #include <linux/const.h>
- /*
- * min()/max()/clamp() macros must accomplish three things:
- *
- * - avoid multiple evaluations of the arguments (so side-effects like
- * "x++" happen only once) when non-constant.
- * - perform strict type-checking (to generate warnings instead of
- * nasty runtime surprises). See the "unnecessary" pointer comparison
- * in __typecheck().
- * - retain result as a constant expressions when called with only
- * constant expressions (to avoid tripping VLA warnings in stack
- * allocation usage).
- */
- #define __typecheck(x, y) \
- (!!(sizeof((typeof(x) *)1 == (typeof(y) *)1)))
- #define __no_side_effects(x, y) \
- (__is_constexpr(x) && __is_constexpr(y))
- #define __safe_cmp(x, y) \
- (__typecheck(x, y) && __no_side_effects(x, y))
- #define __cmp(x, y, op) ((x) op (y) ? (x) : (y))
- #define __cmp_once(x, y, unique_x, unique_y, op) ({ \
- typeof(x) unique_x = (x); \
- typeof(y) unique_y = (y); \
- __cmp(unique_x, unique_y, op); })
- #define __careful_cmp(x, y, op) \
- __builtin_choose_expr(__safe_cmp(x, y), \
- __cmp(x, y, op), \
- __cmp_once(x, y, __UNIQUE_ID(__x), __UNIQUE_ID(__y), op))
- /**
- * min - return minimum of two values of the same or compatible types
- * @x: first value
- * @y: second value
- */
- #define min(x, y) __careful_cmp(x, y, <)
- /**
- * max - return maximum of two values of the same or compatible types
- * @x: first value
- * @y: second value
- */
- #define max(x, y) __careful_cmp(x, y, >)
- /**
- * min3 - return minimum of three values
- * @x: first value
- * @y: second value
- * @z: third value
- */
- #define min3(x, y, z) min((typeof(x))min(x, y), z)
- /**
- * max3 - return maximum of three values
- * @x: first value
- * @y: second value
- * @z: third value
- */
- #define max3(x, y, z) max((typeof(x))max(x, y), z)
- /**
- * min_not_zero - return the minimum that is _not_ zero, unless both are zero
- * @x: value1
- * @y: value2
- */
- #define min_not_zero(x, y) ({ \
- typeof(x) __x = (x); \
- typeof(y) __y = (y); \
- __x == 0 ? __y : ((__y == 0) ? __x : min(__x, __y)); })
- /**
- * clamp - return a value clamped to a given range with strict typechecking
- * @val: current value
- * @lo: lowest allowable value
- * @hi: highest allowable value
- *
- * This macro does strict typechecking of @lo/@hi to make sure they are of the
- * same type as @val. See the unnecessary pointer comparisons.
- */
- #define clamp(val, lo, hi) min((typeof(val))max(val, lo), hi)
- /*
- * ..and if you can't take the strict
- * types, you can specify one yourself.
- *
- * Or not use min/max/clamp at all, of course.
- */
- /**
- * min_t - return minimum of two values, using the specified type
- * @type: data type to use
- * @x: first value
- * @y: second value
- */
- #define min_t(type, x, y) __careful_cmp((type)(x), (type)(y), <)
- /**
- * max_t - return maximum of two values, using the specified type
- * @type: data type to use
- * @x: first value
- * @y: second value
- */
- #define max_t(type, x, y) __careful_cmp((type)(x), (type)(y), >)
- /**
- * clamp_t - return a value clamped to a given range using a given type
- * @type: the type of variable to use
- * @val: current value
- * @lo: minimum allowable value
- * @hi: maximum allowable value
- *
- * This macro does no typechecking and uses temporary variables of type
- * @type to make all the comparisons.
- */
- #define clamp_t(type, val, lo, hi) min_t(type, max_t(type, val, lo), hi)
- /**
- * clamp_val - return a value clamped to a given range using val's type
- * @val: current value
- * @lo: minimum allowable value
- * @hi: maximum allowable value
- *
- * This macro does no typechecking and uses temporary variables of whatever
- * type the input argument @val is. This is useful when @val is an unsigned
- * type and @lo and @hi are literals that will otherwise be assigned a signed
- * integer type.
- */
- #define clamp_val(val, lo, hi) clamp_t(typeof(val), val, lo, hi)
- /**
- * swap - swap values of @a and @b
- * @a: first value
- * @b: second value
- */
- #define swap(a, b) \
- do { typeof(a) __tmp = (a); (a) = (b); (b) = __tmp; } while (0)
- #endif /* _LINUX_MINMAX_H */
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