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b296a6d5 AS |
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 | ||
5efcecd9 | 40 | #define __clamp(val, lo, hi) \ |
2122e2a4 | 41 | ((val) >= (hi) ? (hi) : ((val) <= (lo) ? (lo) : (val))) |
5efcecd9 JD |
42 | |
43 | #define __clamp_once(val, lo, hi, unique_val, unique_lo, unique_hi) ({ \ | |
44 | typeof(val) unique_val = (val); \ | |
45 | typeof(lo) unique_lo = (lo); \ | |
46 | typeof(hi) unique_hi = (hi); \ | |
47 | __clamp(unique_val, unique_lo, unique_hi); }) | |
48 | ||
49 | #define __clamp_input_check(lo, hi) \ | |
50 | (BUILD_BUG_ON_ZERO(__builtin_choose_expr( \ | |
51 | __is_constexpr((lo) > (hi)), (lo) > (hi), false))) | |
52 | ||
53 | #define __careful_clamp(val, lo, hi) ({ \ | |
54 | __clamp_input_check(lo, hi) + \ | |
55 | __builtin_choose_expr(__typecheck(val, lo) && __typecheck(val, hi) && \ | |
56 | __typecheck(hi, lo) && __is_constexpr(val) && \ | |
57 | __is_constexpr(lo) && __is_constexpr(hi), \ | |
58 | __clamp(val, lo, hi), \ | |
59 | __clamp_once(val, lo, hi, __UNIQUE_ID(__val), \ | |
60 | __UNIQUE_ID(__lo), __UNIQUE_ID(__hi))); }) | |
61 | ||
b296a6d5 AS |
62 | /** |
63 | * min - return minimum of two values of the same or compatible types | |
64 | * @x: first value | |
65 | * @y: second value | |
66 | */ | |
67 | #define min(x, y) __careful_cmp(x, y, <) | |
68 | ||
69 | /** | |
70 | * max - return maximum of two values of the same or compatible types | |
71 | * @x: first value | |
72 | * @y: second value | |
73 | */ | |
74 | #define max(x, y) __careful_cmp(x, y, >) | |
75 | ||
76 | /** | |
77 | * min3 - return minimum of three values | |
78 | * @x: first value | |
79 | * @y: second value | |
80 | * @z: third value | |
81 | */ | |
82 | #define min3(x, y, z) min((typeof(x))min(x, y), z) | |
83 | ||
84 | /** | |
85 | * max3 - return maximum of three values | |
86 | * @x: first value | |
87 | * @y: second value | |
88 | * @z: third value | |
89 | */ | |
90 | #define max3(x, y, z) max((typeof(x))max(x, y), z) | |
91 | ||
92 | /** | |
93 | * min_not_zero - return the minimum that is _not_ zero, unless both are zero | |
94 | * @x: value1 | |
95 | * @y: value2 | |
96 | */ | |
97 | #define min_not_zero(x, y) ({ \ | |
98 | typeof(x) __x = (x); \ | |
99 | typeof(y) __y = (y); \ | |
100 | __x == 0 ? __y : ((__y == 0) ? __x : min(__x, __y)); }) | |
101 | ||
102 | /** | |
103 | * clamp - return a value clamped to a given range with strict typechecking | |
104 | * @val: current value | |
105 | * @lo: lowest allowable value | |
106 | * @hi: highest allowable value | |
107 | * | |
108 | * This macro does strict typechecking of @lo/@hi to make sure they are of the | |
109 | * same type as @val. See the unnecessary pointer comparisons. | |
110 | */ | |
5efcecd9 | 111 | #define clamp(val, lo, hi) __careful_clamp(val, lo, hi) |
b296a6d5 AS |
112 | |
113 | /* | |
114 | * ..and if you can't take the strict | |
115 | * types, you can specify one yourself. | |
116 | * | |
117 | * Or not use min/max/clamp at all, of course. | |
118 | */ | |
119 | ||
120 | /** | |
121 | * min_t - return minimum of two values, using the specified type | |
122 | * @type: data type to use | |
123 | * @x: first value | |
124 | * @y: second value | |
125 | */ | |
126 | #define min_t(type, x, y) __careful_cmp((type)(x), (type)(y), <) | |
127 | ||
128 | /** | |
129 | * max_t - return maximum of two values, using the specified type | |
130 | * @type: data type to use | |
131 | * @x: first value | |
132 | * @y: second value | |
133 | */ | |
134 | #define max_t(type, x, y) __careful_cmp((type)(x), (type)(y), >) | |
135 | ||
136 | /** | |
137 | * clamp_t - return a value clamped to a given range using a given type | |
138 | * @type: the type of variable to use | |
139 | * @val: current value | |
140 | * @lo: minimum allowable value | |
141 | * @hi: maximum allowable value | |
142 | * | |
143 | * This macro does no typechecking and uses temporary variables of type | |
144 | * @type to make all the comparisons. | |
145 | */ | |
5efcecd9 | 146 | #define clamp_t(type, val, lo, hi) __careful_clamp((type)(val), (type)(lo), (type)(hi)) |
b296a6d5 AS |
147 | |
148 | /** | |
149 | * clamp_val - return a value clamped to a given range using val's type | |
150 | * @val: current value | |
151 | * @lo: minimum allowable value | |
152 | * @hi: maximum allowable value | |
153 | * | |
154 | * This macro does no typechecking and uses temporary variables of whatever | |
155 | * type the input argument @val is. This is useful when @val is an unsigned | |
156 | * type and @lo and @hi are literals that will otherwise be assigned a signed | |
157 | * integer type. | |
158 | */ | |
159 | #define clamp_val(val, lo, hi) clamp_t(typeof(val), val, lo, hi) | |
160 | ||
161 | /** | |
162 | * swap - swap values of @a and @b | |
163 | * @a: first value | |
164 | * @b: second value | |
165 | */ | |
166 | #define swap(a, b) \ | |
167 | do { typeof(a) __tmp = (a); (a) = (b); (b) = __tmp; } while (0) | |
168 | ||
169 | #endif /* _LINUX_MINMAX_H */ |