[PATCH 1/2] interpolate.[ch]: Add a function to find which interpolations are active.

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

Some substitutions require pretty expensive operations.  So it makes
sense to find out which are needed to begin with.  Call
interp_find_active() to set the new "active" field in the interpolation
table.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---

	This is the patch that Rene proposed, but squashed into my earlier
	patch.

 interpolate.c |   20 ++++++++++++++++++++
 interpolate.h |    3 +++
 2 files changed, 23 insertions(+), 0 deletions(-)

diff --git a/interpolate.c b/interpolate.c
index 6ef53f2..bbd89bb 100644
--- a/interpolate.c
+++ b/interpolate.c
@@ -102,3 +102,23 @@ unsigned long interpolate(char *result, unsigned long reslen,
 		*dest = '\0';
 	return newlen;
 }
+
+void interp_find_active(const char *orig,
+		struct interp *interps, int ninterps)
+{
+	char c;
+	int i;
+
+	for (i = 0; i < ninterps; i++)
+		interps[i].active = 0;
+
+	while ((c = *(orig++)))
+		if (c == '%')
+			/* Try to match an interpolation string. */
+			for (i = 0; i < ninterps; i++)
+				if (!prefixcmp(orig, interps[i].name + 1)) {
+					interps[i].active = 1;
+					orig += strlen(interps[i].name + 1);
+					break;
+				}
+}
diff --git a/interpolate.h b/interpolate.h
index 77407e6..d23531a 100644
--- a/interpolate.h
+++ b/interpolate.h
@@ -14,6 +14,7 @@
 struct interp {
 	const char *name;
 	char *value;
+	int active:1;
 };
 
 extern void interp_set_entry(struct interp *table, int slot, const char *value);
@@ -22,5 +23,7 @@ extern void interp_clear_table(struct interp *table, int ninterps);
 extern unsigned long interpolate(char *result, unsigned long reslen,
 				 const char *orig,
 				 const struct interp *interps, int ninterps);
+extern void interp_find_active(const char *orig,
+				struct interp *interps, int ninterps);
 
 #endif /* INTERPOLATE_H */
-- 
1.5.3.5.1597.g7191