Sync with maint

[thirdparty/git.git] / sha1-array.h

diff --git a/sha1-array.h b/sha1-array.h
index 55d016c4bf7bf56936f034b7550996d1b7ca6473..dc1bca9c9aea6cdbf001b8d43d2e43b99c034d81 100644 (file)
--- a/sha1-array.h
+++ b/sha1-array.h
@@ -1,6 +1,52 @@
 #ifndef SHA1_ARRAY_H
 #define SHA1_ARRAY_H
 
+/**
+ * The API provides storage and manipulation of sets of object identifiers.
+ * The emphasis is on storage and processing efficiency, making them suitable
+ * for large lists. Note that the ordering of items is not preserved over some
+ * operations.
+ *
+ * Examples
+ * --------
+ * -----------------------------------------
+ * int print_callback(const struct object_id *oid,
+ *                 void *data)
+ * {
+ *     printf("%s\n", oid_to_hex(oid));
+ *     return 0; // always continue
+ * }
+ *
+ * void some_func(void)
+ * {
+ *     struct sha1_array hashes = OID_ARRAY_INIT;
+ *     struct object_id oid;
+ *
+ *     // Read objects into our set
+ *     while (read_object_from_stdin(oid.hash))
+ *         oid_array_append(&hashes, &oid);
+ *
+ *     // Check if some objects are in our set
+ *     while (read_object_from_stdin(oid.hash)) {
+ *         if (oid_array_lookup(&hashes, &oid) >= 0)
+ *             printf("it's in there!\n");
+ *
+ *          // Print the unique set of objects. We could also have
+ *          // avoided adding duplicate objects in the first place,
+ *          // but we would end up re-sorting the array repeatedly.
+ *          // Instead, this will sort once and then skip duplicates
+ *          // in linear time.
+ *
+ *         oid_array_for_each_unique(&hashes, print_callback, NULL);
+ *     }
+ */
+
+/**
+ * A single array of object IDs. This should be initialized by assignment from
+ * `OID_ARRAY_INIT`. The `oid` member contains the actual data. The `nr` member
+ * contains the number of items in the set. The `alloc` and `sorted` members
+ * are used internally, and should not be needed by API callers.
+ */
 struct oid_array {
        struct object_id *oid;
        int nr;
@@ -10,18 +56,52 @@ struct oid_array {
 
 #define OID_ARRAY_INIT { NULL, 0, 0, 0 }
 
+/**
+ * Add an item to the set. The object ID will be placed at the end of the array
+ * (but note that some operations below may lose this ordering).
+ */
 void oid_array_append(struct oid_array *array, const struct object_id *oid);
+
+/**
+ * Perform a binary search of the array for a specific object ID. If found,
+ * returns the offset (in number of elements) of the object ID. If not found,
+ * returns a negative integer. If the array is not sorted, this function has
+ * the side effect of sorting it.
+ */
 int oid_array_lookup(struct oid_array *array, const struct object_id *oid);
+
+/**
+ * Free all memory associated with the array and return it to the initial,
+ * empty state.
+ */
 void oid_array_clear(struct oid_array *array);
 
 typedef int (*for_each_oid_fn)(const struct object_id *oid,
                               void *data);
+/**
+ * Iterate over each element of the list, executing the callback function for
+ * each one. Does not sort the list, so any custom hash order is retained.
+ * If the callback returns a non-zero value, the iteration ends immediately
+ * and the callback's return is propagated; otherwise, 0 is returned.
+ */
 int oid_array_for_each(struct oid_array *array,
                       for_each_oid_fn fn,
                       void *data);
+
+/**
+ * Iterate over each unique element of the list in sorted order, but otherwise
+ * behave like `oid_array_for_each`. If the array is not sorted, this function
+ * has the side effect of sorting it.
+ */
 int oid_array_for_each_unique(struct oid_array *array,
                              for_each_oid_fn fn,
                              void *data);
+
+/**
+ * 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.
+ */
 void oid_array_filter(struct oid_array *array,
                      for_each_oid_fn want,
                      void *cbdata);