path-list documentation: document all functions and data structures
Signed-off-by: Miklos Vajna <vmiklos@frugalware.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Miklos Vajna committed
Jun 15, 2008 at 14:06 UTC
328a4750b155df9de29cac007c74e2412d244620
1 file changed
+121
-4
Documentation/technical/api-path-list.txt
+121
-4
@@ -1,9 +1,126 @@
1
path-list API
2
=============
3
4
-Talk about <path-list.h>, things like
4
+The path_list API offers a data structure and functions to handle sorted
5
+and unsorted string lists.
6
6
-* it is not just paths but strings in general;
7
-* the calling sequence.
7
+The name is a bit misleading, a path_list may store not only paths but
8
+strings in general.
9
9
-(Dscho)
10
+The caller:
11
+
12
+. Allocates and clears a `struct path_list` variable.
13
+
14
+. Initializes the members. You might want to set the flag `strdup_paths`
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
++
19
+If you need something advanced, you can manually malloc() the `items`
20
+member (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 `path_list_append` or `path_list_insert`.
24
+
25
+. Can check if a string is in the list using `path_list_has_path` or
26
+ `unsorted_path_list_has_path` and get it from the list using
27
+ `path_list_lookup` for sorted lists.
28
+
29
+. Can sort an unsorted list using `sort_path_list`.
30
+
31
+. Finally it should free the list using `path_list_clear`.
32
+
33
+Example:
34
+
35
+----
36
+struct path_list list;
37
+int i;
38
+
39
+memset(&list, 0, sizeof(struct path_list));
40
+path_list_append("foo", &list);
41
+path_list_append("bar", &list);
42
+for (i = 0; i < list.nr; i++)
43
+ printf("%s\n", list.items[i].path)
44
+----
45
+
46
+NOTE: It is more efficient to build an unsorted list and sort it
47
+afterwards, instead of building a sorted list (`O(n log n)` instead of
48
+`O(n^2)`).
49
++
50
+However, if you use the list to check if a certain string was added
51
+already, you should not do that (using unsorted_path_list_has_path()),
52
+because the complexity would be quadratic again (but with a worse factor).
53
+
54
+Functions
55
+---------
56
+
57
+* General ones (works with sorted and unsorted lists as well)
58
+
59
+`print_path_list`::
60
+
61
+ Dump a path_list to stdout, useful mainly for debugging purposes. It
62
+ can take an optional header argument and it writes out the
63
+ string-pointer pairs of the path_list, each one in its own line.
64
+
65
+`path_list_clear`::
66
+
67
+ Free a path_list. The `path` pointer of the items will be freed in case
68
+ the `strdup_paths` member of the path_list is set. The second parameter
69
+ controls if the `util` pointer of the items should be freed or not.
70
+
71
+* Functions for sorted lists only
72
+
73
+`path_list_has_path`::
74
+
75
+ Determine if the path_list has a given string or not.
76
+
77
+`path_list_insert`::
78
+
79
+ Insert a new element to the path_list. The returned pointer can be handy
80
+ if you want to write something to the `util` pointer of the
81
+ path_list_item containing the just added string.
82
++
83
+Since this function uses xrealloc() (which die()s if it fails) if the
84
+list needs to grow, it is safe not to check the pointer. I.e. you may
85
+write `path_list_insert(...)->util = ...;`.
86
+
87
+`path_list_lookup`::
88
+
89
+ Look up a given string in the path_list, returning the containing
90
+ path_list_item. If the string is not found, NULL is returned.
91
+
92
+* Functions for unsorted lists only
93
+
94
+`path_list_append`::
95
+
96
+ Append a new string to the end of the path_list.
97
+
98
+`sort_path_list`::
99
+
100
+ Make an unsorted list sorted.
101
+
102
+`unsorted_path_list_has_path`::
103
+
104
+ It's like `path_list_has_path()` but for unsorted lists.
105
++
106
+This function needs to look through all items, as opposed to its
107
+counterpart for sorted lists, which performs a binary search.
108
+
109
+Data structures
110
+---------------
111
+
112
+* `struct path_list_item`
113
+
114
+Represents an item of the list. The `path` member is a pointer to the
115
+string, and you may use the `util` member for any purpose, if you want.
116
+
117
+* `struct path_list`
118
+
119
+Represents the list itself.
120
+
121
+. The array of items are available via the `items` member.
122
+. The `nr` member contains the number of items stored in the list.
123
+. The `alloc` member is used to avoid reallocating at every insertion.
124
+ You should not tamper with it.
125
+. Setting the `strdup_paths` member to 1 will strdup() the strings
126
+ before adding them, see above.