Initial cloud-services repo - gateway service + pkg modules

pkg/utils/randomvalues/randomvalues.go

@@ -0,0 +1,129 @@
+package randomvalues
+
+import (
+	"crypto/rand"
+	"encoding/binary"
+	"fmt"
+	"math/big"
+	"strconv"
+	"sync"
+	"time"
+
+	"fiskerinc.com/modules/utils/mt19937"
+)
+
+type Generator struct {
+	characters  string
+	counter     int32
+	maxUniform  int32
+	onceUniform sync.Once
+	uniform     *mt19937.UniformIntDistribution
+	mt          *mt19937.MT19937
+}
+
+func NewGenerator(allowedchars string) Generator {
+	if len(allowedchars) == 0 {
+		allowedchars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
+	}
+	instance := Generator{
+		characters: allowedchars,
+		maxUniform: 255,
+	}
+	val, _ := instance.GetUInt32()
+	instance.counter = int32(val)
+
+	return instance
+}
+
+func (g *Generator) GetBytes(length int) ([]byte, error) {
+	result := make([]byte, length)
+	_, err := rand.Read(result)
+	if err != nil {
+		return nil, err
+	}
+
+	return result, nil
+}
+
+func (g *Generator) GetString(length int) (string, error) {
+	result := make([]byte, length)
+	for i := 0; i < length; i++ {
+		num, err := rand.Int(rand.Reader, big.NewInt(int64(len(g.characters))))
+		if err != nil {
+			return "", err
+		}
+		result[i] = g.characters[num.Int64()]
+	}
+
+	return string(result), nil
+}
+
+func (g *Generator) GetUInt64() (uint64, error) {
+	buf := make([]byte, 8)
+	_, err := rand.Read(buf)
+	if err != nil {
+		return 0, err
+	}
+	return binary.LittleEndian.Uint64(buf), nil
+}
+
+func (g *Generator) GetUInt32() (uint32, error) {
+	buf := make([]byte, 4)
+	_, err := rand.Read(buf)
+	if err != nil {
+		return 0, err
+	}
+	return binary.LittleEndian.Uint32(buf), nil
+}
+
+func (g *Generator) GetInt(max int) int {
+	result, _ := rand.Int(rand.Reader, big.NewInt(int64(max)))
+	return int(result.Int64())
+}
+
+func (g *Generator) GetHex() (string, error) {
+	value, err := g.GetUInt64()
+	if err != nil {
+		return "", err
+	}
+
+	return fmt.Sprintf("%016s", strconv.FormatUint(value, 16)), nil
+}
+
+func (g *Generator) getUniformIntDistribution() *mt19937.UniformIntDistribution {
+	g.onceUniform.Do(func() {
+		if g.uniform != nil {
+			return
+		}
+		g.mt = mt19937.New()
+		g.uniform = mt19937.DistInt64(g.mt, 0, 255)
+	})
+
+	return g.uniform
+}
+
+func (g *Generator) GetUnformDistInt() int {
+	dist := g.getUniformIntDistribution()
+	return int(dist.Int64())
+}
+
+func (g *Generator) GetUniformDistHex() (string, error) {
+	now := time.Now().UnixNano()
+	result := uint64(now) << 32
+	d := g.GetUnformDistInt() & 0xFF
+	result |= uint64(d << 24)
+	d = g.GetUnformDistInt() & 0xFF
+	result |= uint64(d << 16)
+	c := g.counter & 0xFFFF
+	result |= uint64(c)
+	g.counter++
+
+	return fmt.Sprintf("%016s", strconv.FormatUint(result, 16)), nil
+}
+
+func (g *Generator) Close() {
+	g.counter = 0
+	g.characters = ""
+	g.mt = nil
+	g.uniform = nil
+}