strbuf: allow strbuf_split to work on non-strbufs

The strbuf_split function takes a strbuf as input, and
outputs a list of strbufs. However, there is no reason that
the input has to be a strbuf, and not an arbitrary buffer.

This patch adds strbuf_split_buf for a length-delimited
buffer, and strbuf_split_str for NUL-terminated strings.
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

strbuf.c

@@ -101,19 +101,19 @@ void strbuf_ltrim(struct strbuf *sb)
 	sb->buf[sb->len] = '\0';
 }
 
-struct strbuf **strbuf_split_max(const struct strbuf *sb, int delim, int max)
+struct strbuf **strbuf_split_buf(const char *str, size_t slen, int delim, int max)
 {
 	int alloc = 2, pos = 0;
-	char *n, *p;
+	const char *n, *p;
 	struct strbuf **ret;
 	struct strbuf *t;
 
 	ret = xcalloc(alloc, sizeof(struct strbuf *));
-	p = n = sb->buf;
-	while (n < sb->buf + sb->len) {
+	p = n = str;
+	while (n < str + slen) {
 		int len;
 		if (max <= 0 || pos + 1 < max)
-			n = memchr(n, delim, sb->len - (n - sb->buf));
+			n = memchr(n, delim, slen - (n - str));
 		else
 			n = NULL;
 		if (pos + 1 >= alloc) {
@@ -121,7 +121,7 @@ struct strbuf **strbuf_split_max(const struct strbuf *sb, int delim, int max)
 			ret = xrealloc(ret, sizeof(struct strbuf *) * alloc);
 		}
 		if (!n)
-			n = sb->buf + sb->len - 1;
+			n = str + slen - 1;
 		len = n - p + 1;
 		t = xmalloc(sizeof(struct strbuf));
 		strbuf_init(t, len);

strbuf.h

@@ -47,8 +47,18 @@ extern void strbuf_rtrim(struct strbuf *);
 extern void strbuf_ltrim(struct strbuf *);
 extern int strbuf_cmp(const struct strbuf *, const struct strbuf *);
 
-extern struct strbuf **strbuf_split_max(const struct strbuf *,
+extern struct strbuf **strbuf_split_buf(const char *, size_t,
 					int delim, int max);
+static inline struct strbuf **strbuf_split_str(const char *str,
+					       int delim, int max)
+{
+	return strbuf_split_buf(str, strlen(str), delim, max);
+}
+static inline struct strbuf **strbuf_split_max(const struct strbuf *sb,
+						int delim, int max)
+{
+	return strbuf_split_buf(sb->buf, sb->len, delim, max);
+}
 static inline struct strbuf **strbuf_split(const struct strbuf *sb, int delim)
 {
 	return strbuf_split_max(sb, delim, 0);