Documentation/technical/api-string-list.txt

   1 string-list API
   2 ===============
   3
   4 The string_list API offers a data structure and functions to handle sorted
   5 and unsorted string lists.
   6
   7 The 'string_list' struct used to be called 'path_list', but was renamed
   8 because it is not specific to paths.
   9
  10 The 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 +
  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 `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
  34 Example:
  35
  36 ----
  37 struct string_list list;
  38 int i;
  39
  40 memset(&list, 0, sizeof(struct string_list));
  41 string_list_append(&list, "foo");
  42 string_list_append(&list, "bar");
  43 for (i = 0; i < list.nr; i++)
  44         printf("%s\n", list.items[i].string)
  45 ----
  46
  47 NOTE: It is more efficient to build an unsorted list and sort it
  48 afterwards, instead of building a sorted list (`O(n log n)` instead of
  49 `O(n^2)`).
  50 +
  51 However, if you use the list to check if a certain string was added
  52 already, you should not do that (using unsorted_string_list_has_string()),
  53 because the complexity would be quadratic again (but with a worse factor).
  54
  55 Functions
  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 +
  85 Since this function uses xrealloc() (which die()s if it fails) if the
  86 list needs to grow, it is safe not to check the pointer. I.e. you may
  87 write `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
 108 `unsorted_string_list_lookup`::
 109
 110         It's like `string_list_lookup()` but for unsorted lists.
 111 +
 112 The above two functions need to look through all items, as opposed to their
 113 counterpart for sorted lists, which performs a binary search.
 114
 115 Data structures
 116 ---------------
 117
 118 * `struct string_list_item`
 119
 120 Represents an item of the list. The `string` member is a pointer to the
 121 string, and you may use the `util` member for any purpose, if you want.
 122
 123 * `struct string_list`
 124
 125 Represents the list itself.
 126
 127 . The array of items are available via the `items` member.
 128 . The `nr` member contains the number of items stored in the list.
 129 . The `alloc` member is used to avoid reallocating at every insertion.
 130   You should not tamper with it.
 131 . Setting the `strdup_strings` member to 1 will strdup() the strings
 132   before adding them, see above.