X-Git-Url: https://git.ozlabs.org/?p=ccan;a=blobdiff_plain;f=ccan%2Fbytestring%2Fbytestring.h;fp=ccan%2Fbytestring%2Fbytestring.h;h=abc7dd7bb0424bb684bdd5000006cfce97cc8578;hp=bd525601eb3a71cb40c050838db1f76268b5530b;hb=4008ec0eb0f9a42827db7dd36d6e00d3c50409e7;hpb=c06054cd124670216d147c2e0660aab3c3fa683c

diff --git a/ccan/bytestring/bytestring.h b/ccan/bytestring/bytestring.h
index bd525601..abc7dd7b 100644
--- a/ccan/bytestring/bytestring.h
+++ b/ccan/bytestring/bytestring.h
@@ -95,4 +95,31 @@ static inline char bytestring_byte(struct bytestring s, size_t n)
 	return s.ptr[n];
 }
 
+/**
+ * bytestring_slice - extract a substring from a bytestring
+ * @s: bytestring
+ * @start, @end: indexes
+ *
+ * Return a sub-bytestring of @s, starting at byte index @start, and
+ * running to, but not including byte @end.  If @end is before start,
+ * returns a zero-length bytestring.  If @start is out of range,
+ * return a zero length bytestring at the end of @s.
+ *
+ * Note that this doesn't copy or allocate anything - the returned
+ * bytestring occupies (some of) the same memory as the given
+ * bytestring.
+ */
+static inline struct bytestring bytestring_slice(struct bytestring s,
+						 size_t start, size_t end)
+{
+	if (start > s.len)
+		start = s.len;
+	if (end > s.len)
+		end = s.len;
+	if (end < start)
+		end = start;
+
+	return bytestring(s.ptr + start, end - start);
+}
+
 #endif /* CCAN_BYTESTRING_H_ */