Rename path_list to string_list
[git/git.git] / Documentation / technical / api-string-list.txt
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c455c87c
JS
1string-list API
2===============
3
4The string_list API offers a data structure and functions to handle sorted
5and unsorted string lists.
6
7The 'string_list' struct used to be called 'path_list', but was renamed
8because it is not specific to paths.
9
10The caller:
11
12. Allocates and clears a `struct string_list` variable.
13
14. Initializes the members. You might want to set the flag `strdup_strings`
15 if the strings should be strdup()ed. For example, this is necessary
16 when you add something like git_path("..."), since that function returns
17 a static buffer that will change with the next call to git_path().
18+
19If you need something advanced, you can manually malloc() the `items`
20member (you need this if you add things later) and you should set the
21`nr` and `alloc` members in that case, too.
22
23. Adds new items to the list, using `string_list_append` or
24 `string_list_insert`.
25
26. Can check if a string is in the list using `string_list_has_string` or
27 `unsorted_string_list_has_string` and get it from the list using
28 `string_list_lookup` for sorted lists.
29
30. Can sort an unsorted list using `sort_string_list`.
31
32. Finally it should free the list using `string_list_clear`.
33
34Example:
35
36----
37struct string_list list;
38int i;
39
40memset(&list, 0, sizeof(struct string_list));
41string_list_append("foo", &list);
42string_list_append("bar", &list);
43for (i = 0; i < list.nr; i++)
44 printf("%s\n", list.items[i].path)
45----
46
47NOTE: It is more efficient to build an unsorted list and sort it
48afterwards, instead of building a sorted list (`O(n log n)` instead of
49`O(n^2)`).
50+
51However, if you use the list to check if a certain string was added
52already, you should not do that (using unsorted_string_list_has_string()),
53because the complexity would be quadratic again (but with a worse factor).
54
55Functions
56---------
57
58* General ones (works with sorted and unsorted lists as well)
59
60`print_string_list`::
61
62 Dump a string_list to stdout, useful mainly for debugging purposes. It
63 can take an optional header argument and it writes out the
64 string-pointer pairs of the string_list, each one in its own line.
65
66`string_list_clear`::
67
68 Free a string_list. The `string` pointer of the items will be freed in
69 case the `strdup_strings` member of the string_list is set. The second
70 parameter controls if the `util` pointer of the items should be freed
71 or not.
72
73* Functions for sorted lists only
74
75`string_list_has_string`::
76
77 Determine if the string_list has a given string or not.
78
79`string_list_insert`::
80
81 Insert a new element to the string_list. The returned pointer can be
82 handy if you want to write something to the `util` pointer of the
83 string_list_item containing the just added string.
84+
85Since this function uses xrealloc() (which die()s if it fails) if the
86list needs to grow, it is safe not to check the pointer. I.e. you may
87write `string_list_insert(...)->util = ...;`.
88
89`string_list_lookup`::
90
91 Look up a given string in the string_list, returning the containing
92 string_list_item. If the string is not found, NULL is returned.
93
94* Functions for unsorted lists only
95
96`string_list_append`::
97
98 Append a new string to the end of the string_list.
99
100`sort_string_list`::
101
102 Make an unsorted list sorted.
103
104`unsorted_string_list_has_string`::
105
106 It's like `string_list_has_string()` but for unsorted lists.
107+
108This function needs to look through all items, as opposed to its
109counterpart for sorted lists, which performs a binary search.
110
111Data structures
112---------------
113
114* `struct string_list_item`
115
116Represents an item of the list. The `path` member is a pointer to the
117string, and you may use the `util` member for any purpose, if you want.
118
119* `struct string_list`
120
121Represents the list itself.
122
123. The array of items are available via the `items` member.
124. The `nr` member contains the number of items stored in the list.
125. The `alloc` member is used to avoid reallocating at every insertion.
126 You should not tamper with it.
127. Setting the `strdup_strings` member to 1 will strdup() the strings
128 before adding them, see above.