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