Initial cloud-services repo - gateway service + pkg modules

pkg/utils/mt19937/uniform_int_distribution.go

@@ -0,0 +1,49 @@
+package mt19937
+
+import (
+	"log"
+)
+
+type UniformIntDistribution struct {
+	m_min int64
+	m_max int64
+	m_eng *MT19937
+}
+
+func DistInt64(eng *MT19937, begin int64, end int64) *UniformIntDistribution {
+	if begin > end {
+		log.Println("ERROR! begin is not allowed to be greater than end!")
+		return nil
+	}
+
+	dist := &UniformIntDistribution{
+		m_min: begin,
+		m_max: end,
+		m_eng: eng,
+	}
+	return dist
+}
+
+func (dist *UniformIntDistribution) Int64() int64 {
+	var rng uint64
+
+	if dist.m_min >= 0 {
+		rng = uint64(dist.m_max) - uint64(dist.m_min)
+	} else if dist.m_max >= 0 {
+		rng = uint64(dist.m_max) + uint64(-(dist.m_min + 1)) + 1
+	} else {
+		rng = uint64(dist.m_max - dist.m_min)
+	}
+
+	if rng == 0 {
+		return dist.m_min
+	} else if rng == ^uint64(0) {
+		return int64(dist.m_eng.Random())
+	}
+	bucket_size := ^uint64(0) / (rng + 1)
+	if ^uint64(0)%(rng+1) == rng {
+		bucket_size++
+	}
+	result := dist.m_eng.Random() / bucket_size
+	return int64(result) + dist.m_min
+}