diff options
Diffstat (limited to 'src/pkg/rand/rand.go')
| -rw-r--r-- | src/pkg/rand/rand.go | 19 |
1 files changed, 17 insertions, 2 deletions
diff --git a/src/pkg/rand/rand.go b/src/pkg/rand/rand.go index 0d7eaa79a..8c1219a7a 100644 --- a/src/pkg/rand/rand.go +++ b/src/pkg/rand/rand.go @@ -62,10 +62,25 @@ func (r *Rand) Int63n(n int64) int64 { } // Int31n returns, as an int32, a non-negative pseudo-random number in [0,n). -func (r *Rand) Int31n(n int32) int32 { return int32(r.Int63n(int64(n))) } +func (r *Rand) Int31n(n int32) int32 { + if n <= 0 { + return 0 + } + max := int32((1 << 31) - 1 - (1<<31)%uint32(n)) + v := r.Int31() + for v > max { + v = r.Int31() + } + return v % n +} // Intn returns, as an int, a non-negative pseudo-random number in [0,n). -func (r *Rand) Intn(n int) int { return int(r.Int63n(int64(n))) } +func (r *Rand) Intn(n int) int { + if n <= 1<<31-1 { + return int(r.Int31n(int32(n))) + } + return int(r.Int63n(int64(n))) +} // Float64 returns, as a float64, a pseudo-random number in [0.0,1.0). func (r *Rand) Float64() float64 { return float64(r.Int63()) / (1 << 63) } |