[management] Improve Base62 encoding/decoding performance and robustness (#3391)

base62/base62.go

@@ -3,56 +3,75 @@ package base62
 import (
 	"fmt"
 	"math"
-	"strings"
 )
 
 const (
-	alphabet = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
-	base     = uint32(len(alphabet))
+	alphabet        = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
+	base            = uint32(len(alphabet))
+	maxBase62Digits = 6 // max number of digits required to encode MaxUint32
+
 )
 
+var (
+	ErrEmptyString = fmt.Errorf("empty string")
+	ErrInvalidChar = fmt.Errorf("invalid character")
+	ErrOverflow    = fmt.Errorf("integer overflow")
+)
+
+// Fixed-size arrays have better performance and lower memory overhead compared to maps for small static sets of data
+var charToIndex [123]int8 // Assuming ASCII from '\0' - 'z'
+
+func init() {
+	for i := range charToIndex {
+		charToIndex[i] = -1
+	}
+	for i, c := range alphabet {
+		charToIndex[c] = int8(i)
+	}
+}
+
 // Encode encodes a uint32 value to a base62 string.
-func Encode(num uint32) string {
-	if num == 0 {
-		return string(alphabet[0])
+// The returned string will be between 1-6 characters long.
+func Encode(n uint32) string {
+	if n < base {
+		return string(alphabet[n])
+	}
+	// avoid dynamic memory usage for small, fixed size data
+	buf := [maxBase62Digits]byte{}
+	idx := len(buf)
+
+	for n > 0 {
+		idx--
+		buf[idx] = alphabet[n%base]
+		n /= base
 	}
 
-	var encoded strings.Builder
-
-	for num > 0 {
-		remainder := num % base
-		encoded.WriteByte(alphabet[remainder])
-		num /= base
-	}
-
-	// Reverse the encoded string
-	encodedString := encoded.String()
-	reversed := reverse(encodedString)
-	return reversed
+	return string(buf[idx:])
 }
 
 // Decode decodes a base62 string to a uint32 value.
+// Returns an error if the input string is empty, contains invalid characters,
+// or would result in integer overflow.
 func Decode(encoded string) (uint32, error) {
+	if len(encoded) == 0 {
+		return 0, ErrEmptyString
+	}
 	var decoded uint32
-	strLen := len(encoded)
-
-	for i, char := range encoded {
-		index := strings.IndexRune(alphabet, char)
+	for _, char := range encoded {
+		index := int8(-1)
+		if int(char) < len(charToIndex) {
+			index = charToIndex[char]
+		}
 		if index < 0 {
-			return 0, fmt.Errorf("invalid character: %c", char)
+			return 0, fmt.Errorf("%w: %c", ErrInvalidChar, char)
+		}
+		// Add overflow check when calculating the decoded value to prevent silent overflow of uint32
+		if decoded > (math.MaxUint32-uint32(index))/base {
+			return 0, fmt.Errorf("%w: %s", ErrOverflow, encoded)
 		}
 
-		decoded += uint32(index) * uint32(math.Pow(float64(base), float64(strLen-i-1)))
+		decoded = decoded*base + uint32(index)
 	}
 
 	return decoded, nil
 }
-
-// Reverse a string.
-func reverse(s string) string {
-	runes := []rune(s)
-	for i, j := 0, len(runes)-1; i < j; i, j = i+1, j-1 {
-		runes[i], runes[j] = runes[j], runes[i]
-	}
-	return string(runes)
-}