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

[Stefan Beller]

Helped-by: Junio C Hamano <gits...@pobox.com>
Signed-off-by: Stefan Beller <sbel...@google.com>
Signed-off-by: Junio C Hamano <gits...@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 b94e0ec0f5..d922e94e3f 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 */
-- 
2.20.0.rc1.387.gf8505762e3-goog