lib: Add a way to find the postiion of a trailing number

At present it is not possible to find out which part of the string is the
number part and which is before it. Add a new variant which provides this
feature, so we can separate the two in the caller.

Signed-off-by: Simon Glass <sjg@chromium.org>

include/vsprintf.h

@@ -121,6 +121,24 @@ long trailing_strtol(const char *str);
  */
 long trailing_strtoln(const char *str, const char *end);
 
+/**
+ * trailing_strtoln_end() - extract trailing integer from a fixed-length string
+ *
+ * Given a fixed-length string this finds a trailing number on the string
+ * and returns it. For example, "abc123" would return 123. Only the
+ * characters between @str and @end - 1 are examined. If @end is NULL, it is
+ * set to str + strlen(str).
+ *
+ * @str:	String to examine
+ * @end:	Pointer to end of string to examine, or NULL to use the
+ *		whole string
+ * @endp:	If non-NULL, this is set to point to the character where the
+ *	number starts, e.g. for "mmc0" this would be point to the '0'; if no
+ *	trailing number is found, it is set to the end of the string
+ * Return: training number if found, else -1
+ */
+long trailing_strtoln_end(const char *str, const char *end, char const **endp);
+
 /**
  * panic() - Print a message and reset/hang
  *

lib/strto.c

@@ -183,7 +183,7 @@ long long simple_strtoll(const char *cp, char **endp, unsigned int base)
 	return simple_strtoull(cp, endp, base);
 }
 
-long trailing_strtoln(const char *str, const char *end)
+long trailing_strtoln_end(const char *str, const char *end, char const **endp)
 {
 	const char *p;
 
@@ -192,14 +192,24 @@ long trailing_strtoln(const char *str, const char *end)
 	p = end - 1;
 	if (p > str && isdigit(*p)) {
 		do {
-			if (!isdigit(p[-1]))
+			if (!isdigit(p[-1])) {
+				if (endp)
+					*endp = p;
 				return dectoul(p, NULL);
+			}
 		} while (--p > str);
 	}
+	if (endp)
+		*endp = end;
 
 	return -1;
 }
 
+long trailing_strtoln(const char *str, const char *end)
+{
+	return trailing_strtoln_end(str, end, NULL);
+}
+
 long trailing_strtol(const char *str)
 {
 	return trailing_strtoln(str, NULL);

test/str_ut.c

@@ -244,7 +244,9 @@ STR_TEST(str_xtoa, 0);
 
 static int str_trailing(struct unit_test_state *uts)
 {
-	char str1[] = "abc123def";
+	const char str1[] = "abc123def";
+	const char str2[] = "abc123def456";
+	const char *end;
 
 	ut_asserteq(-1, trailing_strtol(""));
 	ut_asserteq(-1, trailing_strtol("123"));
@@ -259,6 +261,15 @@ static int str_trailing(struct unit_test_state *uts)
 
 	ut_asserteq(3, trailing_strtol("a3"));
 
+	ut_asserteq(123, trailing_strtoln_end(str1, str1 + 6, &end));
+	ut_asserteq(3, end - str1);
+
+	ut_asserteq(-1, trailing_strtoln_end(str1, str1 + 7, &end));
+	ut_asserteq(7, end - str1);
+
+	ut_asserteq(456, trailing_strtoln_end(str2, NULL, &end));
+	ut_asserteq(9, end - str2);
+
 	return 0;
 }
 STR_TEST(str_trailing, 0);