First commit

internal/generate/id.go

@@ -0,0 +1,40 @@
+package generate
+
+import (
+	"crypto/rand"
+	"encoding/binary"
+	mrand "math/rand"
+	"strconv"
+	"strings"
+)
+
+// ID generates an ID using crypto-random, falling back to math random when that fails
+// to avoid disrupting operation because of a faulty RNG. Database implementations does
+// not need to use this if some other scheme improves storage.
+func ID(prefix string, length int) string {
+	var data [32]byte
+
+	result := strings.Builder{}
+	result.Grow(length + 32)
+	result.WriteString(prefix)
+
+	pos := 0
+	for result.Len() < length {
+		if pos == 0 {
+			randRead(data[:])
+		}
+
+		result.WriteString(strconv.FormatUint(binary.BigEndian.Uint64(data[pos:pos+8]), 36))
+
+		pos = (pos + 8) % 32
+	}
+
+	return result.String()[:length]
+}
+
+func randRead(data []byte) {
+	n, err := rand.Read(data)
+	if err != nil {
+		mrand.Read(data[n:])
+	}
+}