move countDigits to separate file

flow/datatypes/bigint.go

@@ -1,12 +1,33 @@
 package datatypes
 
 import (
+	"math"
 	"math/big"
 )
 
+var tenInt = big.NewInt(10)
+
 func CountDigits(bi *big.Int) int {
-	if bi.Sign() < 0 {
-		return len(bi.String()) - 1
+	if bi.IsInt64() {
+		i64 := bi.Int64()
+		// restrict fast path to integers with exact conversion to float64
+		if i64 <= (1<<53) && i64 >= -(1<<53) {
+			if i64 == 0 {
+				return 1
+			}
+			return int(math.Log10(math.Abs(float64(i64)))) + 1
+		}
+	}
+
+	estimatedNumDigits := int(float64(bi.BitLen()) / math.Log2(10))
+
+	// estimatedNumDigits (lg10) may be off by 1, need to verify
+	digitsBigInt := big.NewInt(int64(estimatedNumDigits))
+	errorCorrectionUnit := digitsBigInt.Exp(tenInt, digitsBigInt, nil)
+
+	if bi.CmpAbs(errorCorrectionUnit) >= 0 {
+		return estimatedNumDigits + 1
 	}
-	return len(bi.String())
+
+	return estimatedNumDigits
 }

flow/model/qvalue/avro_converter.go

@@ -4,8 +4,6 @@ import (
 	"errors"
 	"fmt"
 	"log/slog"
-	"math"
-	"math/big"
 	"time"
 
 	"github.com/google/uuid"
@@ -445,33 +443,6 @@ func (c *QValueAvroConverter) processNullableUnion(
 	return value, nil
 }
 
-var tenInt = big.NewInt(10)
-
-func countDigits(bi *big.Int) int {
-	if bi.IsInt64() {
-		i64 := bi.Int64()
-		// restrict fast path to integers with exact conversion to float64
-		if i64 <= (1<<53) && i64 >= -(1<<53) {
-			if i64 == 0 {
-				return 1
-			}
-			return int(math.Log10(math.Abs(float64(i64)))) + 1
-		}
-	}
-
-	estimatedNumDigits := int(float64(bi.BitLen()) / math.Log2(10))
-
-	// estimatedNumDigits (lg10) may be off by 1, need to verify
-	digitsBigInt := big.NewInt(int64(estimatedNumDigits))
-	errorCorrectionUnit := digitsBigInt.Exp(tenInt, digitsBigInt, nil)
-
-	if bi.CmpAbs(errorCorrectionUnit) >= 0 {
-		return estimatedNumDigits + 1
-	}
-
-	return estimatedNumDigits
-}
-
 func (c *QValueAvroConverter) processNumeric(num decimal.Decimal) interface{} {
 	num, err := TruncateOrLogNumeric(num, c.Precision, c.Scale, c.TargetDWH)
 	if err != nil {