[PATCH 2/4] Add a new function, filter_string_list()

[Michael Haggerty <mhagger@alum.mit.edu>]

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
---
 Documentation/technical/api-string-list.txt |  8 ++++++++
 string-list.c                               | 17 +++++++++++++++++
 string-list.h                               |  9 +++++++++
 3 files changed, 34 insertions(+)

diff --git a/Documentation/technical/api-string-list.txt b/Documentation/technical/api-string-list.txt
index 3b959a2..15b8072 100644
--- a/Documentation/technical/api-string-list.txt
+++ b/Documentation/technical/api-string-list.txt
@@ -60,6 +60,14 @@ Functions
 
 * General ones (works with sorted and unsorted lists as well)
 
+`filter_string_list`::
+
+	Apply a function to each item in a list, retaining only the
+	items for which the function returns true.  If free_util is
+	true, call free() on the util members of any items that have
+	to be deleted.  Preserve the order of the items that are
+	retained.
+
 `print_string_list`::
 
 	Dump a string_list to stdout, useful mainly for debugging purposes. It
diff --git a/string-list.c b/string-list.c
index 110449c..72610ce 100644
--- a/string-list.c
+++ b/string-list.c
@@ -102,6 +102,23 @@ int for_each_string_list(struct string_list *list,
 	return ret;
 }
 
+void filter_string_list(struct string_list *list, int free_util,
+			string_list_each_func_t fn, void *cb_data)
+{
+	int src, dst = 0;
+	for (src = 0; src < list->nr; src++) {
+		if (fn(&list->items[src], cb_data)) {
+			list->items[dst++] = list->items[src];
+		} else {
+			if (list->strdup_strings)
+				free(list->items[src].string);
+			if (free_util)
+				free(list->items[src].util);
+		}
+	}
+	list->nr = dst;
+}
+
 void string_list_clear(struct string_list *list, int free_util)
 {
 	if (list->items) {
diff --git a/string-list.h b/string-list.h
index 7e51d03..84996aa 100644
--- a/string-list.h
+++ b/string-list.h
@@ -29,6 +29,15 @@ int for_each_string_list(struct string_list *list,
 #define for_each_string_list_item(item,list) \
 	for (item = (list)->items; item < (list)->items + (list)->nr; ++item)
 
+/*
+ * Apply fn to each item in list, retaining only the ones for which
+ * the function returns true.  If free_util is true, call free() on
+ * the util members of any items that have to be deleted.  Preserve
+ * the order of the items that are retained.
+ */
+void filter_string_list(struct string_list *list, int free_util,
+			string_list_each_func_t fn, void *cb_data);
+
 /* Use these functions only on sorted lists: */
 int string_list_has_string(const struct string_list *list, const char *string);
 int string_list_find_insert_index(const struct string_list *list, const char *string,
-- 
1.7.11.3