string-list.h: move documentation from Documentation/api/ into header

This mirrors commit 'bdfdaa497 ("strbuf.h: integrate api-strbuf.txt
documentation, 2015-01-16") which did the same for strbuf.h:

* API documentation uses /** */ to set it apart from other comments.

* Function names were stripped from the comments.

* Ordering of the header was adjusted to follow the one from the text
  file.

* Edited some existing comments from string-list.h for consistency.

Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 162 insertions, 30 deletions

diff --git a/string-list.h b/string-list.h
index 79ae567cbc..ff8f6094a3 100644
--- a/string-list.h
+++ b/string-list.h
@@ -1,6 +1,69 @@
 #ifndef STRING_LIST_H
 #define STRING_LIST_H
 
+/**
+ * The string_list API offers a data structure and functions to handle
+ * sorted and unsorted arrays of strings.  A "sorted" list is one whose
+ * entries are sorted by string value in `strcmp()` order.
+ *
+ * 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 `string_list_sort`.
+ *
+ * . 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).
+ */
+
+/**
+ * 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_item {
 	char *string;
 	void *util;
@@ -8,6 +71,18 @@ struct string_list_item {
 
 typedef int (*compare_strings_fn)(const char *, const char *);
 
+/**
+ * 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.
+ * . The `compare_strings_fn` member is used to specify a custom compare
+ *   function, otherwise `strcmp()` is used as the default function.
+ */
 struct string_list {
 	struct string_list_item *items;
 	unsigned int nr, alloc;
@@ -18,35 +93,65 @@ struct string_list {
 #define STRING_LIST_INIT_NODUP { NULL, 0, 0, 0, NULL }
 #define STRING_LIST_INIT_DUP   { NULL, 0, 0, 1, NULL }
 
+/* General functions which work with both sorted and unsorted lists. */
+
+/**
+ * Initialize the members of the string_list, set `strdup_strings`
+ * member according to the value of the second parameter.
+ */
 void string_list_init(struct string_list *list, int strdup_strings);
 
+/** Callback function type for for_each_string_list */
+typedef int (*string_list_each_func_t)(struct string_list_item *, void *);
+
+/**
+ * Apply `want` to each item in `list`, retaining only the ones 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.
+ */
+void filter_string_list(struct string_list *list, int free_util,
+			string_list_each_func_t want, void *cb_data);
+
+/**
+ * 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.
+ */
 void print_string_list(const struct string_list *p, const char *text);
+
+/**
+ * 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.
+ */
 void string_list_clear(struct string_list *list, int free_util);
 
-/* Use this function to call a custom clear function on each util pointer */
-/* The string associated with the util pointer is passed as the second argument */
+/**
+ * Callback type for `string_list_clear_func`.  The string associated
+ * with the util pointer is passed as the second argument
+ */
 typedef void (*string_list_clear_func_t)(void *p, const char *str);
+
+/** Call a custom clear function on each util pointer */
 void string_list_clear_func(struct string_list *list, string_list_clear_func_t clearfunc);
 
-/* Use this function or the macro below to iterate over each item */
-typedef int (*string_list_each_func_t)(struct string_list_item *, void *);
+/**
+ * Apply `func` to each item. If `func` returns nonzero, the
+ * iteration aborts and the return value is propagated.
+ */
 int for_each_string_list(struct string_list *list,
-			 string_list_each_func_t, void *cb_data);
+			 string_list_each_func_t func, void *cb_data);
+
+/** Iterate over each item, as a macro. */
 #define for_each_string_list_item(item,list)            \
 	for (item = (list)->items;                      \
 	     item && item < (list)->items + (list)->nr; \
 	     ++item)
 
-/*
- * Apply want to each item in list, retaining only the ones 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.
- */
-void filter_string_list(struct string_list *list, int free_util,
-			string_list_each_func_t want, void *cb_data);
-
-/*
+/**
  * 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.
@@ -54,25 +159,34 @@ void filter_string_list(struct string_list *list, int free_util,
 void string_list_remove_empty_items(struct string_list *list, int free_util);
 
 /* Use these functions only on sorted lists: */
+
+/** Determine if the string_list has a given string or not. */
 int string_list_has_string(const struct string_list *list, const char *string);
 int string_list_find_insert_index(const struct string_list *list, const char *string,
 				  int negative_existing_index);
-/*
- * Inserts the given string into the sorted list.
- * If the string already exists, the list is not altered.
- * Returns the string_list_item, the string is part of.
+
+/**
+ * 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 = ...;`.
  */
 struct string_list_item *string_list_insert(struct string_list *list, const char *string);
 
-/*
- * Removes the given string from the sorted list.
- * If the string doesn't exist, the list is not altered.
+/**
+ * Remove the given string from the sorted list.  If the string
+ * doesn't exist, the list is not altered.
  */
 extern void string_list_remove(struct string_list *list, const char *string,
 			       int free_util);
 
-/*
- * Checks if the given string is part of a sorted list. If it is part of the list,
+/**
+ * Check if the given string is part of a sorted list. If it is part of the list,
  * return the coresponding string_list_item, NULL otherwise.
  */
 struct string_list_item *string_list_lookup(struct string_list *list, const char *string);
@@ -87,14 +201,14 @@ void string_list_remove_duplicates(struct string_list *sorted_list, int free_uti
 
 /* Use these functions only on unsorted lists: */
 
-/*
+/**
  * Add string to the end of list.  If list->strdup_string is set, then
  * string is copied; otherwise the new string_list_entry refers to the
  * input string.
  */
 struct string_list_item *string_list_append(struct string_list *list, const char *string);
 
-/*
+/**
  * Like string_list_append(), except string is never copied.  When
  * list->strdup_strings is set, this function can be used to hand
  * ownership of a malloc()ed string to list without making an extra
@@ -102,16 +216,34 @@ struct string_list_item *string_list_append(struct string_list *list, const char
  */
 struct string_list_item *string_list_append_nodup(struct string_list *list, char *string);
 
+/**
+ * Sort the list's entries by string value in `strcmp()` order.
+ */
 void string_list_sort(struct string_list *list);
+
+/**
+ * Like `string_list_has_string()` but for unsorted lists. Linear in
+ * size of the list.
+ */
 int unsorted_string_list_has_string(struct string_list *list, const char *string);
+
+/**
+ * Like `string_list_lookup()` but for unsorted lists. Linear in size
+ * of the list.
+ */
 struct string_list_item *unsorted_string_list_lookup(struct string_list *list,
 						     const char *string);
-
+/**
+ * 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.
+ */
 void unsorted_string_list_delete_item(struct string_list *list, int i, int free_util);
 
-/*
- * Split string into substrings on character delim and append the
- * substrings to list.  The input string is not modified.
+/**
+ * Split string into substrings on character `delim` and append the
+ * substrings to `list`.  The input string is not modified.
  * list->strdup_strings must be set, as new memory needs to be
  * allocated to hold the substrings.  If maxsplit is non-negative,
  * then split at most maxsplit times.  Return the number of substrings