| 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
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| 2 | #ifndef _LINUX_MINMAX_H |
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| 3 | #define _LINUX_MINMAX_H |
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| 4 | |
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| 5 | #include <linux/const.h> |
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| 6 | |
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| 7 | /* |
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| 8 | * min()/max()/clamp() macros must accomplish three things: |
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| 9 | * |
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| 10 | * - avoid multiple evaluations of the arguments (so side-effects like |
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| 11 | * "x++" happen only once) when non-constant. |
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| 12 | * - perform strict type-checking (to generate warnings instead of |
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| 13 | * nasty runtime surprises). See the "unnecessary" pointer comparison |
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| 14 | * in __typecheck(). |
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| 15 | * - retain result as a constant expressions when called with only |
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| 16 | * constant expressions (to avoid tripping VLA warnings in stack |
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| 17 | * allocation usage). |
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| 18 | */ |
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| 19 | #define __typecheck(x, y) \ |
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| 20 | (!!(sizeof((typeof(x) *)1 == (typeof(y) *)1))) |
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| 21 | |
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| 22 | #define __no_side_effects(x, y) \ |
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| 23 | (__is_constexpr(x) && __is_constexpr(y)) |
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| 24 | |
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| 25 | #define __safe_cmp(x, y) \ |
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| 26 | (__typecheck(x, y) && __no_side_effects(x, y)) |
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| 27 | |
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| 28 | #define __cmp(x, y, op) ((x) op (y) ? (x) : (y)) |
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| 29 | |
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| 30 | #define __cmp_once(x, y, unique_x, unique_y, op) ({ \ |
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| 31 | typeof(x) unique_x = (x); \ |
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| 32 | typeof(y) unique_y = (y); \ |
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| 33 | __cmp(unique_x, unique_y, op); }) |
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| 34 | |
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| 35 | #define __careful_cmp(x, y, op) \ |
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| 36 | __builtin_choose_expr(__safe_cmp(x, y), \ |
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| 37 | __cmp(x, y, op), \ |
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| 38 | __cmp_once(x, y, __UNIQUE_ID(__x), __UNIQUE_ID(__y), op)) |
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| 39 | |
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| 40 | /** |
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| 41 | * min - return minimum of two values of the same or compatible types |
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| 42 | * @x: first value |
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| 43 | * @y: second value |
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| 44 | */ |
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| 45 | #define min(x, y) __careful_cmp(x, y, <) |
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| 46 | |
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| 47 | /** |
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| 48 | * max - return maximum of two values of the same or compatible types |
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| 49 | * @x: first value |
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| 50 | * @y: second value |
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| 51 | */ |
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| 52 | #define max(x, y) __careful_cmp(x, y, >) |
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| 53 | |
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| 54 | /** |
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| 55 | * min3 - return minimum of three values |
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| 56 | * @x: first value |
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| 57 | * @y: second value |
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| 58 | * @z: third value |
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| 59 | */ |
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| 60 | #define min3(x, y, z) min((typeof(x))min(x, y), z) |
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| 61 | |
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| 62 | /** |
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| 63 | * max3 - return maximum of three values |
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| 64 | * @x: first value |
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| 65 | * @y: second value |
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| 66 | * @z: third value |
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| 67 | */ |
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| 68 | #define max3(x, y, z) max((typeof(x))max(x, y), z) |
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| 69 | |
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| 70 | /** |
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| 71 | * min_not_zero - return the minimum that is _not_ zero, unless both are zero |
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| 72 | * @x: value1 |
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| 73 | * @y: value2 |
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| 74 | */ |
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| 75 | #define min_not_zero(x, y) ({ \ |
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| 76 | typeof(x) __x = (x); \ |
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| 77 | typeof(y) __y = (y); \ |
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| 78 | __x == 0 ? __y : ((__y == 0) ? __x : min(__x, __y)); }) |
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| 79 | |
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| 80 | /** |
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| 81 | * clamp - return a value clamped to a given range with strict typechecking |
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| 82 | * @val: current value |
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| 83 | * @lo: lowest allowable value |
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| 84 | * @hi: highest allowable value |
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| 85 | * |
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| 86 | * This macro does strict typechecking of @lo/@hi to make sure they are of the |
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| 87 | * same type as @val. See the unnecessary pointer comparisons. |
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| 88 | */ |
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| 89 | #define clamp(val, lo, hi) min((typeof(val))max(val, lo), hi) |
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| 90 | |
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| 91 | /* |
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| 92 | * ..and if you can't take the strict |
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| 93 | * types, you can specify one yourself. |
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| 94 | * |
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| 95 | * Or not use min/max/clamp at all, of course. |
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| 96 | */ |
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| 97 | |
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| 98 | /** |
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| 99 | * min_t - return minimum of two values, using the specified type |
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| 100 | * @type: data type to use |
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| 101 | * @x: first value |
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| 102 | * @y: second value |
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| 103 | */ |
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| 104 | #define min_t(type, x, y) __careful_cmp((type)(x), (type)(y), <) |
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| 105 | |
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| 106 | /** |
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| 107 | * max_t - return maximum of two values, using the specified type |
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| 108 | * @type: data type to use |
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| 109 | * @x: first value |
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| 110 | * @y: second value |
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| 111 | */ |
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| 112 | #define max_t(type, x, y) __careful_cmp((type)(x), (type)(y), >) |
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| 113 | |
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| 114 | /** |
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| 115 | * clamp_t - return a value clamped to a given range using a given type |
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| 116 | * @type: the type of variable to use |
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| 117 | * @val: current value |
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| 118 | * @lo: minimum allowable value |
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| 119 | * @hi: maximum allowable value |
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| 120 | * |
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| 121 | * This macro does no typechecking and uses temporary variables of type |
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| 122 | * @type to make all the comparisons. |
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| 123 | */ |
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| 124 | #define clamp_t(type, val, lo, hi) min_t(type, max_t(type, val, lo), hi) |
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| 125 | |
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| 126 | /** |
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| 127 | * clamp_val - return a value clamped to a given range using val's type |
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| 128 | * @val: current value |
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| 129 | * @lo: minimum allowable value |
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| 130 | * @hi: maximum allowable value |
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| 131 | * |
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| 132 | * This macro does no typechecking and uses temporary variables of whatever |
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| 133 | * type the input argument @val is. This is useful when @val is an unsigned |
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| 134 | * type and @lo and @hi are literals that will otherwise be assigned a signed |
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| 135 | * integer type. |
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| 136 | */ |
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| 137 | #define clamp_val(val, lo, hi) clamp_t(typeof(val), val, lo, hi) |
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| 138 | |
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| 139 | /** |
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| 140 | * swap - swap values of @a and @b |
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| 141 | * @a: first value |
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| 142 | * @b: second value |
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| 143 | */ |
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| 144 | #define swap(a, b) \ |
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| 145 | do { typeof(a) __tmp = (a); (a) = (b); (b) = __tmp; } while (0) |
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| 146 | |
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| 147 | #endif /* _LINUX_MINMAX_H */ |
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| 148 | |
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