add strbuf_expand_dict_cb(), a helper for simple cases

The new callback function strbuf_expand_dict_cb() can be used together
with strbuf_expand() if there is only a small number of placeholders
for static replacement texts.  It expects its dictionary as an array of
placeholder+value pairs as context parameter, terminated by an entry
with the placeholder member set to NULL.

The new helper is intended to aid converting the remaining calls of
interpolate().  strbuf_expand() is smaller, more flexible and can be
used to go faster than interpolate(), so it should replace the latter.

Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/strbuf.c b/strbuf.c
index 720737d856..13be67e4d3 100644
--- a/strbuf.c
+++ b/strbuf.c
@@ -237,6 +237,22 @@ void strbuf_expand(struct strbuf *sb, const char *format, expand_fn_t fn,
 	}
 }
 
+size_t strbuf_expand_dict_cb(struct strbuf *sb, const char *placeholder,
+		void *context)
+{
+	struct strbuf_expand_dict_entry *e = context;
+	size_t len;
+
+	for (; e->placeholder && (len = strlen(e->placeholder)); e++) {
+		if (!strncmp(placeholder, e->placeholder, len)) {
+			if (e->value)
+				strbuf_addstr(sb, e->value);
+			return len;
+		}
+	}
+	return 0;
+}
+
 size_t strbuf_fread(struct strbuf *sb, size_t size, FILE *f)
 {
 	size_t res;