lib: pull base-guessing logic to helper function

The default base is 10 unless there is a leading zero, in which
case the base will be guessed as 8.

The base will only be guesed as 16 when the string starts with '0x'
the third character is a valid hex digit.
Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/vsprintf.c

@@ -32,6 +32,18 @@
 /* Works only for digits and letters, but small and fast */
 #define TOLOWER(x) ((x) | 0x20)
 
+static unsigned int simple_guess_base(const char *cp)
+{
+	if (cp[0] == '0') {
+		if (TOLOWER(cp[1]) == 'x' && isxdigit(cp[2]))
+			return 16;
+		else
+			return 8;
+	} else {
+		return 10;
+	}
+}
+
 /**
  * simple_strtoul - convert a string to an unsigned long
  * @cp: The start of the string
@@ -40,32 +52,28 @@
  */
 unsigned long simple_strtoul(const char *cp,char **endp,unsigned int base)
 {
-	unsigned long result = 0,value;
+	unsigned long result = 0;
 
-	if (!base) {
-		base = 10;
-		if (*cp == '0') {
-			base = 8;
-			cp++;
-			if ((TOLOWER(*cp) == 'x') && isxdigit(cp[1])) {
-				cp++;
-				base = 16;
-			}
-		}
-	} else if (base == 16) {
-		if (cp[0] == '0' && TOLOWER(cp[1]) == 'x')
+	if (!base)
+		base = simple_guess_base(cp);
+
+	if (base == 16 && cp[0] == '0' && TOLOWER(cp[1]) == 'x')
 		cp += 2;
-	}
-	while (isxdigit(*cp) &&
-	       (value = isdigit(*cp) ? *cp-'0' : TOLOWER(*cp)-'a'+10) < base) {
-		result = result*base + value;
+
+	while (isxdigit(*cp)) {
+		unsigned int value;
+
+		value = isdigit(*cp) ? *cp - '0' : TOLOWER(*cp) - 'a' + 10;
+		if (value >= base)
+			break;
+		result = result * base + value;
 		cp++;
 	}
+
 	if (endp)
 		*endp = (char *)cp;
 	return result;
 }
-
 EXPORT_SYMBOL(simple_strtoul);
 
 /**
@@ -91,32 +99,28 @@ EXPORT_SYMBOL(simple_strtol);
  */
 unsigned long long simple_strtoull(const char *cp,char **endp,unsigned int base)
 {
-	unsigned long long result = 0,value;
+	unsigned long long result = 0;
 
-	if (!base) {
-		base = 10;
-		if (*cp == '0') {
-			base = 8;
-			cp++;
-			if ((TOLOWER(*cp) == 'x') && isxdigit(cp[1])) {
-				cp++;
-				base = 16;
-			}
-		}
-	} else if (base == 16) {
-		if (cp[0] == '0' && TOLOWER(cp[1]) == 'x')
+	if (!base)
+		base = simple_guess_base(cp);
+
+	if (base == 16 && cp[0] == '0' && TOLOWER(cp[1]) == 'x')
 		cp += 2;
-	}
-	while (isxdigit(*cp)
-	 && (value = isdigit(*cp) ? *cp-'0' : TOLOWER(*cp)-'a'+10) < base) {
-		result = result*base + value;
+
+	while (isxdigit(*cp)) {
+		unsigned int value;
+
+		value = isdigit(*cp) ? *cp - '0' : TOLOWER(*cp) - 'a' + 10;
+		if (value >= base)
+			break;
+		result = result * base + value;
 		cp++;
 	}
+
 	if (endp)
 		*endp = (char *)cp;
 	return result;
 }
-
 EXPORT_SYMBOL(simple_strtoull);
 
 /**