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Edit File: minmax.h

/* SPDX-License-Identifier: GPL-2.0 */ #ifndef _LINUX_MINMAX_H #define _LINUX_MINMAX_H #include <linux/build_bug.h> #include <linux/compiler.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. * - Retain result as a constant expressions when called with only * constant expressions (to avoid tripping VLA warnings in stack * allocation usage). * - Perform signed v unsigned type-checking (to generate compile * errors instead of nasty runtime surprises). * - Unsigned char/short are always promoted to signed int and can be * compared against signed or unsigned arguments. * - Unsigned arguments can be compared against non-negative signed constants. * - Comparison of a signed argument against an unsigned constant fails * even if the constant is below __INT_MAX__ and could be cast to int. */ #define __typecheck(x, y) \ (!!(sizeof((typeof(x) *)1 == (typeof(y) *)1))) /* is_signed_type() isn't a constexpr for pointer types */ #define __is_signed(x) \ __builtin_choose_expr(__is_constexpr(is_signed_type(typeof(x))), \ is_signed_type(typeof(x)), 0) /* True for a non-negative signed int constant */ #define __is_noneg_int(x) \ (__builtin_choose_expr(__is_constexpr(x) && __is_signed(x), x, -1) >= 0) #define __types_ok(x, y) \ (__is_signed(x) == __is_signed(y) || \ __is_signed((x) + 0) == __is_signed((y) + 0) || \ __is_noneg_int(x) || __is_noneg_int(y)) #define __cmp_op_min < #define __cmp_op_max > #define __cmp(op, x, y) ((x) __cmp_op_##op (y) ? (x) : (y)) #define __cmp_once(op, x, y, unique_x, unique_y) ({ \ typeof(x) unique_x = (x); \ typeof(y) unique_y = (y); \ static_assert(__types_ok(x, y), \ #op "(" #x ", " #y ") signedness error, fix types or consider u" #op "() before " #op "_t()"); \ __cmp(op, unique_x, unique_y); }) #define __careful_cmp(op, x, y) \ __builtin_choose_expr(__is_constexpr((x) - (y)), \ __cmp(op, x, y), \ __cmp_once(op, x, y, __UNIQUE_ID(__x), __UNIQUE_ID(__y))) #define __clamp(val, lo, hi) \ ((val) >= (hi) ? (hi) : ((val) <= (lo) ? (lo) : (val))) #define __clamp_once(val, lo, hi, unique_val, unique_lo, unique_hi) ({ \ typeof(val) unique_val = (val); \ typeof(lo) unique_lo = (lo); \ typeof(hi) unique_hi = (hi); \ static_assert(__builtin_choose_expr(__is_constexpr((lo) > (hi)), \ (lo) <= (hi), true), \ "clamp() low limit " #lo " greater than high limit " #hi); \ static_assert(__types_ok(val, lo), "clamp() 'lo' signedness error"); \ static_assert(__types_ok(val, hi), "clamp() 'hi' signedness error"); \ __clamp(unique_val, unique_lo, unique_hi); }) #define __careful_clamp(val, lo, hi) ({ \ __builtin_choose_expr(__is_constexpr((val) - (lo) + (hi)), \ __clamp(val, lo, hi), \ __clamp_once(val, lo, hi, __UNIQUE_ID(__val), \ __UNIQUE_ID(__lo), __UNIQUE_ID(__hi))); }) /** * min - return minimum of two values of the same or compatible types * @x: first value * @y: second value */ #define min(x, y) __careful_cmp(min, 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(max, x, y) /** * umin - return minimum of two non-negative values * Signed types are zero extended to match a larger unsigned type. * @x: first value * @y: second value */ #define umin(x, y) \ __careful_cmp(min, (x) + 0u + 0ul + 0ull, (y) + 0u + 0ul + 0ull) /** * umax - return maximum of two non-negative values * @x: first value * @y: second value */ #define umax(x, y) \ __careful_cmp(max, (x) + 0u + 0ul + 0ull, (y) + 0u + 0ul + 0ull) /** * 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) __careful_clamp(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(min, (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(max, (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) __careful_clamp((type)(val), (type)(lo), (type)(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 */