diff options
Diffstat (limited to 'runtime/arith.c')
| -rw-r--r-- | runtime/arith.c | 24 |
1 files changed, 23 insertions, 1 deletions
diff --git a/runtime/arith.c b/runtime/arith.c index 175cc4e8..0200afa6 100644 --- a/runtime/arith.c +++ b/runtime/arith.c @@ -2,9 +2,10 @@ #define _ARITH_C_ /** @file arith. - * @brief Implements 64-bit signed division/multiplication. + * @brief Implements various arithmetic-related helper functions */ + struct context; void _stp_divmod64 (unsigned *errorcount, int64_t x, int64_t y, int64_t *quo, int64_t *rem); @@ -75,5 +76,26 @@ void _stp_divmod64 (unsigned *errorcount, int64_t x, int64_t y, } +/** Return a random integer between -n and n. + * @param n how far from zero to go. Make it positive but less than a million or so. + */ +int _stp_random_pm (int n) +{ + static unsigned long seed; + static int initialized_p = 0; + + if (unlikely (! initialized_p)) + { + seed = (unsigned long) jiffies; + initialized_p = 1; + } + + /* from glibc rand man page */ + seed = seed * 1103515245 + 12345; + + return (seed % (2*n+1)-n); +} + + #endif /* _ARITH_C_ */ |