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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.
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