[PATCH v2 1/7] 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>
---

Notes:
    v1 -> v2:
    - Tokeinize using strsep()+empty-token-check instead of strtok()
    - Return array from strtokv() and pass count in an output pointer,
      rather than the opposite.

 include/string.h |  1 +
 lib/string.c     | 30 ++++++++++++++++++++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/include/string.h b/include/string.h
index 71affe48b6..cb3492ba04 100644
--- a/include/string.h
+++ b/include/string.h
@@ -8,6 +8,7 @@
 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 **strtokv(char *str, const char *delim, int *cntp);
 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..a55f989900 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -593,6 +593,36 @@ char *strsep_unescaped(char **s, const char *ct, char *delim)
         return sbegin;
 }
 
+/**
+ * strtokv - split string into array of tokens based on a delimiter set
+ * @str:	string to split
+ * @delim:	set of delimiter characters
+ * @cntp:	number of tokens
+ *
+ * Split @str into non-empty tokens delimited by spans of characters
+ * from @delim, and store the numbers of tokens in @cntp.
+ *
+ * Return: The allocated array of tokens, which the caller is
+ * responsible for freeing.
+ */
+char **strtokv(char *str, const char *delim, int *cntp)
+{
+	char *tok, **vec = NULL;
+	int cnt = 0;
+
+	while ((tok = strsep(&str, delim))) {
+		if (*tok == '\0')
+			continue;
+
+		vec = xrealloc(vec, (cnt + 1) * sizeof(*vec));
+		vec[cnt++] = tok;
+	}
+
+	*cntp = cnt;
+	return vec;
+}
+EXPORT_SYMBOL(strtokv);
+
 #ifndef __HAVE_ARCH_STRSWAB
 /**
  * strswab - swap adjacent even and odd bytes in %NUL-terminated string
-- 
2.43.0