include/linux/tnum.h

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