common: unify hex prefix check code

common/bytes.go

@@ -17,7 +17,11 @@
 // Package common contains various helper functions.
 package common
 
-import "encoding/hex"
+import (
+	"encoding/hex"
+
+	"github.com/ethereum/go-ethereum/common/hexutil"
+)
 
 // ToHex returns the hex representation of b, prefixed with '0x'.
 // For empty slices, the return value is "0x0".
@@ -43,10 +47,8 @@ func ToHexArray(b [][]byte) []string {
 // FromHex returns the bytes represented by the hexadecimal string s.
 // s may be prefixed with "0x".
 func FromHex(s string) []byte {
-	if len(s) > 1 {
-		if s[0:2] == "0x" || s[0:2] == "0X" {
-			s = s[2:]
-		}
+	if hexutil.Has0xPrefix(s) {
+		s = s[2:]
 	}
 	if len(s)%2 == 1 {
 		s = "0" + s
@@ -65,11 +67,6 @@ func CopyBytes(b []byte) (copiedBytes []byte) {
 	return
 }
 
-// hasHexPrefix validates str begins with '0x' or '0X'.
-func hasHexPrefix(str string) bool {
-	return len(str) >= 2 && str[0] == '0' && (str[1] == 'x' || str[1] == 'X')
-}
-
 // isHexCharacter returns bool of c being a valid hexadecimal.
 func isHexCharacter(c byte) bool {
 	return ('0' <= c && c <= '9') || ('a' <= c && c <= 'f') || ('A' <= c && c <= 'F')

common/hexutil/hexutil.go

@@ -61,7 +61,7 @@ func Decode(input string) ([]byte, error) {
 	if len(input) == 0 {
 		return nil, ErrEmptyString
 	}
-	if !has0xPrefix(input) {
+	if !Has0xPrefix(input) {
 		return nil, ErrMissingPrefix
 	}
 	b, err := hex.DecodeString(input[2:])
@@ -185,15 +185,16 @@ func EncodeBig(bigint *big.Int) string {
 	return fmt.Sprintf("%#x", bigint)
 }
 
-func has0xPrefix(input string) bool {
+// Has0xPrefix validates input begins with '0x' or '0X'.
+func Has0xPrefix(input string) bool {
 	return len(input) >= 2 && input[0] == '0' && (input[1] == 'x' || input[1] == 'X')
 }
 
 func checkNumber(input string) (raw string, err error) {
 	if len(input) == 0 {
 		return "", ErrEmptyString
 	}
-	if !has0xPrefix(input) {
+	if !Has0xPrefix(input) {
 		return "", ErrMissingPrefix
 	}
 	input = input[2:]

common/math/big.go

@@ -20,6 +20,8 @@ package math
 import (
 	"fmt"
 	"math/big"
+
+	"github.com/ethereum/go-ethereum/common/hexutil"
 )
 
 // Various big integer limit values.
@@ -75,7 +77,7 @@ func ParseBig256(s string) (*big.Int, bool) {
 	}
 	var bigint *big.Int
 	var ok bool
-	if len(s) >= 2 && (s[:2] == "0x" || s[:2] == "0X") {
+	if hexutil.Has0xPrefix(s) {
 		bigint, ok = new(big.Int).SetString(s[2:], 16)
 	} else {
 		bigint, ok = new(big.Int).SetString(s, 10)

common/math/integer.go

@@ -19,6 +19,8 @@ package math
 import (
 	"fmt"
 	"strconv"
+
+	"github.com/ethereum/go-ethereum/common/hexutil"
 )
 
 // Integer limit values.
@@ -61,7 +63,7 @@ func ParseUint64(s string) (uint64, bool) {
 	if s == "" {
 		return 0, true
 	}
-	if len(s) >= 2 && (s[:2] == "0x" || s[:2] == "0X") {
+	if hexutil.Has0xPrefix(s) {
 		v, err := strconv.ParseUint(s[2:], 16, 64)
 		return v, err == nil
 	}

common/types.go

@@ -193,7 +193,7 @@ func HexToAddress(s string) Address { return BytesToAddress(FromHex(s)) }
 // IsHexAddress verifies whether a string can represent a valid hex-encoded
 // Ethereum address or not.
 func IsHexAddress(s string) bool {
-	if hasHexPrefix(s) {
+	if hexutil.Has0xPrefix(s) {
 		s = s[2:]
 	}
 	return len(s) == 2*AddressLength && isHex(s)