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1 | /* SPDX-License-Identifier: GPL-2.0 */ |
2 | #ifndef _LINUX_MINMAX_H | |
3 | #define _LINUX_MINMAX_H | |
4 | ||
f747e666 RF |
5 | #include <linux/const.h> |
6 | ||
b296a6d5 AS |
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 | ||
b296a6d5 AS |
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 */ |