bytestring: Implement bytestring_spn() and bytestring_cspn()

Add bytestring_spn() and bytestring_cspn() functions which, in analogy to
strspn() and strcspn() return the lengths of initial sub-bytestrings which
either contain only a given set of bytes, or anything except a given set
of bytes.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

ccan/bytestring/bytestring.c

+/* Licensed under LGPLv2+ - see LICENSE file for details */
+#include "config.h"
+
+#include <ccan/bytestring/bytestring.h>
+
+size_t bytestring_spn(struct bytestring s, struct bytestring accept)
+{
+	size_t i;
+
+	for (i = 0; i < s.len; i++)
+		if (bytestring_index(accept, s.ptr[i]) == NULL)
+			return i;
+
+	return s.len;
+}
+
+size_t bytestring_cspn(struct bytestring s, struct bytestring reject)
+{
+	size_t i;
+
+	for (i = 0; i < s.len; i++)
+		if (bytestring_index(reject, s.ptr[i]) != NULL)
+			return i;
+
+	return s.len;
+}

ccan/bytestring/bytestring.h

@@ -200,4 +200,24 @@ static inline struct bytestring bytestring_bytestring(struct bytestring haystack
 		return bytestring_NULL;
 }
 
+/**
+ * bytestring_spn - search a bytestring for a set of bytes
+ * @s: a bytestring
+ * @accept: a bytestring containing a set of bytes to accept
+ *
+ * Returns the length, in bytes, of the initial segment of @s which
+ * consists entirely of characters in @accept.
+ */
+size_t bytestring_spn(struct bytestring s, struct bytestring accept);
+
+/**
+ * bytestring_cspn - search a bytestring for a set of bytes (complemented)
+ * @s: a bytestring
+ * @reject: a bytestring containing a set of bytes to reject
+ *
+ * Returns the length, in bytes, of the initial segment of @s which
+ * consists entirely of characters not in @reject.
+ */
+size_t bytestring_cspn(struct bytestring s, struct bytestring reject);
+
 #endif /* CCAN_BYTESTRING_H_ */

ccan/bytestring/test/run.c

@@ -3,6 +3,8 @@
 #include <ccan/bytestring/bytestring.h>
 #include <ccan/tap/tap.h>
 
+#include <ccan/bytestring/bytestring.c>
+
 #define TEST_STRING	"test string"
 #define TEST_STRING_2	"abc\0def"
 
@@ -14,7 +16,7 @@ int main(void)
 	struct bytestring bs, bs1, bs2, bs3, bs4, bs5, bs6;
 
 	/* This is how many tests you plan to run */
-	plan_tests(47);
+	plan_tests(53);
 
 	bs = bytestring(str1, sizeof(str1) - 1);
 	ok1(bs.ptr == str1);
@@ -88,6 +90,16 @@ int main(void)
 	ok1(bytestring_eq(bytestring_bytestring(bs2, bytestring_NULL),
 			  bytestring(bs2.ptr, 0)));
 
+
+	ok1(bytestring_spn(bs1, BYTESTRING("est")) == 4);
+	ok1(bytestring_cspn(bs1, BYTESTRING(" ")) == 4);
+
+	ok1(bytestring_spn(bs2, BYTESTRING("z")) == 0);
+	ok1(bytestring_cspn(bs2, BYTESTRING("\0")) == 3);
+
+	ok1(bytestring_spn(bs1, BYTESTRING("eginrst ")) == bs1.len);
+	ok1(bytestring_cspn(bs2, BYTESTRING("z")) == bs2.len);
+
 	/* This exits depending on whether all tests passed */
 	return exit_status();
 }