[PATCH 1/9] sha1-array: provide oid_array_filter

[Stefan Beller <sbeller@google.com>]

Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 Documentation/technical/api-oid-array.txt |  5 +++++
 sha1-array.c                              | 17 +++++++++++++++++
 sha1-array.h                              |  3 +++
 3 files changed, 25 insertions(+)

diff --git a/Documentation/technical/api-oid-array.txt b/Documentation/technical/api-oid-array.txt
index 9febfb1d52..c97428c2c3 100644
--- a/Documentation/technical/api-oid-array.txt
+++ b/Documentation/technical/api-oid-array.txt
@@ -48,6 +48,11 @@ Functions
 	is not sorted, this function has the side effect of sorting
 	it.
 
+`oid_array_filter`::
+	Apply the callback function `want` to each entry in the array,
+	retaining only the entries for which the function returns true.
+	Preserve the order of the entries that are retained.
+
 Examples
 --------
 
diff --git a/sha1-array.c b/sha1-array.c
index 265941fbf4..d505a004bb 100644
--- a/sha1-array.c
+++ b/sha1-array.c
@@ -77,3 +77,20 @@ int oid_array_for_each_unique(struct oid_array *array,
 	}
 	return 0;
 }
+
+void oid_array_filter(struct oid_array *array,
+		      for_each_oid_fn want,
+		      void *cb_data)
+{
+	unsigned nr = array->nr, src, dst;
+	struct object_id *oids = array->oid;
+
+	for (src = dst = 0; src < nr; src++) {
+		if (want(&oids[src], cb_data)) {
+			if (src != dst)
+				oidcpy(&oids[dst], &oids[src]);
+			dst++;
+		}
+	}
+	array->nr = dst;
+}
diff --git a/sha1-array.h b/sha1-array.h
index 232bf95017..55d016c4bf 100644
--- a/sha1-array.h
+++ b/sha1-array.h
@@ -22,5 +22,8 @@ int oid_array_for_each(struct oid_array *array,
 int oid_array_for_each_unique(struct oid_array *array,
 			      for_each_oid_fn fn,
 			      void *data);
+void oid_array_filter(struct oid_array *array,
+		      for_each_oid_fn want,
+		      void *cbdata);
 
 #endif /* SHA1_ARRAY_H */
-- 
2.19.0