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