[PATCH 1/5] string: add strtok/strtokv

[Tobias Waldekranz <tobias@waldekranz.com>]

Add an implementation of libc's standard strtok(3), which is useful
for tokenizing strings.

Also, add a version that will collect all tokens from a string into an
array, which is useful in situations where you need to know how many
tokens there are, and when a token's relative position in the order is
significant.

Signed-off-by: Tobias Waldekranz <tobias@waldekranz.com>
---
 include/string.h |  2 ++
 lib/string.c     | 66 ++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 68 insertions(+)

diff --git a/include/string.h b/include/string.h
index 71affe48b6..c8df8540d8 100644
--- a/include/string.h
+++ b/include/string.h
@@ -8,6 +8,8 @@
 void *mempcpy(void *dest, const void *src, size_t count);
 int strtobool(const char *str, int *val);
 char *strsep_unescaped(char **, const char *, char *);
+char *strtok(char *str, const char *delim);
+int strtokv(char *str, const char *delim, char ***vecp);
 char *stpcpy(char *dest, const char *src);
 bool strends(const char *str, const char *postfix);
 
diff --git a/lib/string.c b/lib/string.c
index 73637cd971..be7e65eb45 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -593,6 +593,72 @@ char *strsep_unescaped(char **s, const char *ct, char *delim)
         return sbegin;
 }
 
+/**
+ * strtok - extract tokens from string
+ * @str:	string to split
+ * @delim:	set of delimiter characters
+ *
+ * The strtok() function breaks up a string into zero or more nonempty
+ * tokens.  On the first call, the string to be parsed should be
+ * specified in @str.  In each subsequent call that should parse the
+ * same string, @str must be NULL.
+ *
+ * @delim specifies a set of bytes that delimit the tokens in the
+ * string.
+ *
+ * Each call to strtok() returns a pointer to a string containing the
+ * next token.  This is done by replacing the first delimiter with a
+ * NUL character, the operation is thus destructive to the string. If
+ * no more tokens are found, strtok() returns NULL.
+ */
+char *strtok(char *str, const char *delim)
+{
+	static char *cursor;
+
+	if (str)
+		cursor = str;
+
+	if (!cursor)
+		return NULL;
+
+	cursor += strspn(cursor, delim);
+	if (*cursor == '\0') {
+		cursor = NULL;
+		return NULL;
+	}
+
+	return strsep(&cursor, delim);
+}
+EXPORT_SYMBOL(strtok);
+
+/**
+ * strtokv - split string into array of tokens based on a delimiter set
+ * @str:	string to split
+ * @delim:	set of delimiter characters
+ * @vecp:	array of tokens
+ *
+ * Split @str into tokens delimited by @delim, using strtok(), and
+ * store the allocated token array in @vecp, which the caller is
+ * responsible for freeing.
+ *
+ * Return: The number of tokens in the array.
+ */
+int strtokv(char *str, const char *delim, char ***vecp)
+{
+	char *tok, **vec = NULL;
+	int cnt = 0;
+
+
+	for (tok = strtok(str, delim); tok; tok = strtok(NULL, delim)) {
+		vec = xrealloc(vec, (cnt + 1) * sizeof(*vec));
+		vec[cnt++] = tok;
+	}
+
+	*vecp = vec;
+	return cnt;
+}
+EXPORT_SYMBOL(strtokv);
+
 #ifndef __HAVE_ARCH_STRSWAB
 /**
  * strswab - swap adjacent even and odd bytes in %NUL-terminated string
-- 
2.43.0