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Diffstat (limited to 'Documentation/technical')
| -rw-r--r-- | Documentation/technical/api-path-list.txt | 125 |
1 files changed, 121 insertions, 4 deletions
diff --git a/Documentation/technical/api-path-list.txt b/Documentation/technical/api-path-list.txt index d07768317..9dbedd0a6 100644 --- a/Documentation/technical/api-path-list.txt +++ b/Documentation/technical/api-path-list.txt @@ -1,9 +1,126 @@ path-list API ============= -Talk about <path-list.h>, things like +The path_list API offers a data structure and functions to handle sorted +and unsorted string lists. -* it is not just paths but strings in general; -* the calling sequence. +The name is a bit misleading, a path_list may store not only paths but +strings in general. -(Dscho) +The caller: + +. Allocates and clears a `struct path_list` variable. + +. Initializes the members. You might want to set the flag `strdup_paths` + 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 `path_list_append` or `path_list_insert`. + +. Can check if a string is in the list using `path_list_has_path` or + `unsorted_path_list_has_path` and get it from the list using + `path_list_lookup` for sorted lists. + +. Can sort an unsorted list using `sort_path_list`. + +. Finally it should free the list using `path_list_clear`. + +Example: + +---- +struct path_list list; +int i; + +memset(&list, 0, sizeof(struct path_list)); +path_list_append("foo", &list); +path_list_append("bar", &list); +for (i = 0; i < list.nr; i++) + printf("%s\n", list.items[i].path) +---- + +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_path_list_has_path()), +because the complexity would be quadratic again (but with a worse factor). + +Functions +--------- + +* General ones (works with sorted and unsorted lists as well) + +`print_path_list`:: + + Dump a path_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 path_list, each one in its own line. + +`path_list_clear`:: + + Free a path_list. The `path` pointer of the items will be freed in case + the `strdup_paths` member of the path_list is set. The second parameter + controls if the `util` pointer of the items should be freed or not. + +* Functions for sorted lists only + +`path_list_has_path`:: + + Determine if the path_list has a given string or not. + +`path_list_insert`:: + + Insert a new element to the path_list. The returned pointer can be handy + if you want to write something to the `util` pointer of the + path_list_item containing the just added string. ++ +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 `path_list_insert(...)->util = ...;`. + +`path_list_lookup`:: + + Look up a given string in the path_list, returning the containing + path_list_item. If the string is not found, NULL is returned. + +* Functions for unsorted lists only + +`path_list_append`:: + + Append a new string to the end of the path_list. + +`sort_path_list`:: + + Make an unsorted list sorted. + +`unsorted_path_list_has_path`:: + + It's like `path_list_has_path()` but for unsorted lists. ++ +This function needs to look through all items, as opposed to its +counterpart for sorted lists, which performs a binary search. + +Data structures +--------------- + +* `struct path_list_item` + +Represents an item of the list. The `path` member is a pointer to the +string, and you may use the `util` member for any purpose, if you want. + +* `struct path_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_paths` member to 1 will strdup() the strings + before adding them, see above. |