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1/* tnum: tracked (or tristate) numbers
2 *
3 * A tnum tracks knowledge about the bits of a value. Each bit can be either
4 * known (0 or 1), or unknown (x). Arithmetic operations on tnums will
5 * propagate the unknown bits such that the tnum result represents all the
6 * possible results for possible values of the operands.
7 */
8#include <linux/types.h>
9
10struct tnum {
11 u64 value;
12 u64 mask;
13};
14
15/* Constructors */
16/* Represent a known constant as a tnum. */
17struct tnum tnum_const(u64 value);
18/* A completely unknown value */
19extern const struct tnum tnum_unknown;
20/* A value that's unknown except that @min <= value <= @max */
21struct tnum tnum_range(u64 min, u64 max);
22
23/* Arithmetic and logical ops */
24/* Shift a tnum left (by a fixed shift) */
25struct tnum tnum_lshift(struct tnum a, u8 shift);
26/* Shift (rsh) a tnum right (by a fixed shift) */
27struct tnum tnum_rshift(struct tnum a, u8 shift);
28/* Shift (arsh) a tnum right (by a fixed min_shift) */
29struct tnum tnum_arshift(struct tnum a, u8 min_shift);
30/* Add two tnums, return @a + @b */
31struct tnum tnum_add(struct tnum a, struct tnum b);
32/* Subtract two tnums, return @a - @b */
33struct tnum tnum_sub(struct tnum a, struct tnum b);
34/* Bitwise-AND, return @a & @b */
35struct tnum tnum_and(struct tnum a, struct tnum b);
36/* Bitwise-OR, return @a | @b */
37struct tnum tnum_or(struct tnum a, struct tnum b);
38/* Bitwise-XOR, return @a ^ @b */
39struct tnum tnum_xor(struct tnum a, struct tnum b);
40/* Multiply two tnums, return @a * @b */
41struct tnum tnum_mul(struct tnum a, struct tnum b);
42
43/* Return a tnum representing numbers satisfying both @a and @b */
44struct tnum tnum_intersect(struct tnum a, struct tnum b);
45
46/* Return @a with all but the lowest @size bytes cleared */
47struct tnum tnum_cast(struct tnum a, u8 size);
48
49/* Returns true if @a is a known constant */
50static inline bool tnum_is_const(struct tnum a)
51{
52 return !a.mask;
53}
54
55/* Returns true if @a == tnum_const(@b) */
56static inline bool tnum_equals_const(struct tnum a, u64 b)
57{
58 return tnum_is_const(a) && a.value == b;
59}
60
61/* Returns true if @a is completely unknown */
62static inline bool tnum_is_unknown(struct tnum a)
63{
64 return !~a.mask;
65}
66
67/* Returns true if @a is known to be a multiple of @size.
68 * @size must be a power of two.
69 */
70bool tnum_is_aligned(struct tnum a, u64 size);
71
72/* Returns true if @b represents a subset of @a. */
73bool tnum_in(struct tnum a, struct tnum b);
74
75/* Formatting functions. These have snprintf-like semantics: they will write
76 * up to @size bytes (including the terminating NUL byte), and return the number
77 * of bytes (excluding the terminating NUL) which would have been written had
78 * sufficient space been available. (Thus tnum_sbin always returns 64.)
79 */
80/* Format a tnum as a pair of hex numbers (value; mask) */
81int tnum_strn(char *str, size_t size, struct tnum a);
82/* Format a tnum as tristate binary expansion */
83int tnum_sbin(char *str, size_t size, struct tnum a);