diff options
Diffstat (limited to 'util.h')
| -rw-r--r-- | util.h | 28 |
1 files changed, 28 insertions, 0 deletions
@@ -227,6 +227,34 @@ int __daemon(int pidfile_fd, int devnull_fd); int fls(unsigned long x); int write_file(const char *path, const char *buf); +/** + * mod_sub() - Modular arithmetic subtraction + * @a: Minued, unsigned value < @m + * @b: Subtrahend, unsigned value < @m + * @m: Modulus, must be less than (UINT_MAX / 2) + * + * Returns (@a - @b) mod @m, correctly handling unsigned underflows. + */ +static inline unsigned mod_sub(unsigned a, unsigned b, unsigned m) +{ + if (a < b) + a += m; + return a - b; +} + +/** + * mod_between() - Determine if a value is in a cyclic range + * @x, @i, @j: Unsigned values < @m + * @m: Modulus + * + * Returns true iff @x is in the cyclic range of values from @i..@j (mod @m), + * inclusive of @i, exclusive of @j. + */ +static inline bool mod_between(unsigned x, unsigned i, unsigned j, unsigned m) +{ + return mod_sub(x, i, m) < mod_sub(j, i, m); +} + /* * Workarounds for https://github.com/llvm/llvm-project/issues/58992 * |