summaryrefslogtreecommitdiff
path: root/Documentation/technical/api-string-list.txt
blob: 20be3488349c2ddbafbd90c0200f2a7d3862a12f (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
string-list API
===============

The string_list API offers a data structure and functions to handle
sorted and unsorted string lists.  A "sorted" list is one whose
entries are sorted by string value in `strcmp()` order.

The 'string_list' struct used to be called 'path_list', but was renamed
because it is not specific to paths.

The caller:

. Allocates and clears a `struct string_list` variable.

. Initializes the members. You might want to set the flag `strdup_strings`
  if the strings should be strdup()ed. For example, this is necessary
  when you add something like git_path("..."), since that function returns
  a static buffer that will change with the next call to git_path().
+
If you need something advanced, you can manually malloc() the `items`
member (you need this if you add things later) and you should set the
`nr` and `alloc` members in that case, too.

. Adds new items to the list, using `string_list_append`,
  `string_list_append_nodup`, `string_list_insert`,
  `string_list_split`, and/or `string_list_split_in_place`.

. Can check if a string is in the list using `string_list_has_string` or
  `unsorted_string_list_has_string` and get it from the list using
  `string_list_lookup` for sorted lists.

. Can sort an unsorted list using `sort_string_list`.

. Can remove duplicate items from a sorted list using
  `string_list_remove_duplicates`.

. Can remove individual items of an unsorted list using
  `unsorted_string_list_delete_item`.

. Can remove items not matching a criterion from a sorted or unsorted
  list using `filter_string_list`, or remove empty strings using
  `string_list_remove_empty_items`.

. Finally it should free the list using `string_list_clear`.

Example:

----
struct string_list list = STRING_LIST_INIT_NODUP;
int i;

string_list_append(&list, "foo");
string_list_append(&list, "bar");
for (i = 0; i < list.nr; i++)
	printf("%s\n", list.items[i].string)
----

NOTE: It is more efficient to build an unsorted list and sort it
afterwards, instead of building a sorted list (`O(n log n)` instead of
`O(n^2)`).
+
However, if you use the list to check if a certain string was added
already, you should not do that (using unsorted_string_list_has_string()),
because the complexity would be quadratic again (but with a worse factor).

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.

`string_list_remove_empty_items`::

	Remove any empty strings from the list.  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
	can take an optional header argument and it writes out the
	string-pointer pairs of the string_list, each one in its own line.

`string_list_clear`::

	Free a string_list. The `string` pointer of the items will be freed in
	case the `strdup_strings` member of the string_list is set. The second
	parameter controls if the `util` pointer of the items should be freed
	or not.

* Functions for sorted lists only

`string_list_has_string`::

	Determine if the string_list has a given string or not.

`string_list_insert`::

	Insert a new element to the string_list. The returned pointer can be
	handy if you want to write something to the `util` pointer of the
	string_list_item containing the just added string. If the given
	string already exists the insertion will be skipped and the
	pointer to the existing item returned.
+
Since this function uses xrealloc() (which die()s if it fails) if the
list needs to grow, it is safe not to check the pointer. I.e. you may
write `string_list_insert(...)->util = ...;`.

`string_list_lookup`::

	Look up a given string in the string_list, returning the containing
	string_list_item. If the string is not found, NULL is returned.

`string_list_remove_duplicates`::

	Remove all but the first of consecutive entries that have the
	same string value.  If free_util is true, call free() on the
	util members of any items that have to be deleted.

* Functions for unsorted lists only

`string_list_append`::

	Append a new string to the end of the string_list.  If
	`strdup_string` is set, then the string argument is copied;
	otherwise the new `string_list_entry` refers to the input
	string.

`string_list_append_nodup`::

	Append a new string to the end of the string_list.  The new
	`string_list_entry` always refers to the input string, even if
	`strdup_string` is set.  This function can be used to hand
	ownership of a malloc()ed string to a `string_list` that has
	`strdup_string` set.

`sort_string_list`::

	Sort the list's entries by string value in `strcmp()` order.

`unsorted_string_list_has_string`::

	It's like `string_list_has_string()` but for unsorted lists.

`unsorted_string_list_lookup`::

	It's like `string_list_lookup()` but for unsorted lists.
+
The above two functions need to look through all items, as opposed to their
counterpart for sorted lists, which performs a binary search.

`unsorted_string_list_delete_item`::

	Remove an item from a string_list. The `string` pointer of the items
	will be freed in case the `strdup_strings` member of the string_list
	is set. The third parameter controls if the `util` pointer of the
	items should be freed or not.

`string_list_split`::
`string_list_split_in_place`::

	Split a string into substrings on a delimiter character and
	append the substrings to a `string_list`.  If `maxsplit` is
	non-negative, then split at most `maxsplit` times.  Return the
	number of substrings appended to the list.
+
`string_list_split` requires a `string_list` that has `strdup_strings`
set to true; it leaves the input string untouched and makes copies of
the substrings in newly-allocated memory.
`string_list_split_in_place` requires a `string_list` that has
`strdup_strings` set to false; it splits the input string in place,
overwriting the delimiter characters with NULs and creating new
string_list_items that point into the original string (the original
string must therefore not be modified or freed while the `string_list`
is in use).


Data structures
---------------

* `struct string_list_item`

Represents an item of the list. The `string` member is a pointer to the
string, and you may use the `util` member for any purpose, if you want.

* `struct string_list`

Represents the list itself.

. The array of items are available via the `items` member.
. The `nr` member contains the number of items stored in the list.
. The `alloc` member is used to avoid reallocating at every insertion.
  You should not tamper with it.
. Setting the `strdup_strings` member to 1 will strdup() the strings
  before adding them, see above.