Commit 7b877620 authored by Rusty Russell's avatar Rusty Russell

From: Joseph Adams <joeyadams3.14159@gmail.com>

The btree patch gives the btree module an intuitive frontend
(btree_insert, btree_remove, btree_lookup) and a built-in ordering
function for strings.  Together, these make it easy to use the btree
module as a dynamic string map.
parent 455572f3
......@@ -12,14 +12,6 @@
* invalidate all iterators pointing to it (including the one passed to the
* insertion or removal function).
*
* btree currently doesn't have convenience functions for the simple tasks of
* "look up by key", "insert a key", and "remove a key". To insert or remove,
* you first have use btree_find* to position an iterator on the
* insertion/removal point, then call btree_insert_at or btree_remove_at using
* that iterator. Since a btree can hold multiple items with the same key,
* it isn't clear how the convenience functions should work yet. I'm open to
* suggestions.
*
* A B-tree (not to be confused with a binary tree) is a data structure that
* performs insertion, removal, and lookup in O(log n) time per operation.
* Although B-trees are typically used for databases and filesystems, this is
......
......@@ -77,6 +77,7 @@ struct btree *btree_new(btree_search_t search)
node->depth = 0;
btree->root = node;
btree->search = search;
btree->multi = false;
return btree;
}
......@@ -86,6 +87,43 @@ void btree_delete(struct btree *btree)
free(btree);
}
bool btree_insert(struct btree *btree, const void *item)
{
btree_iterator iter;
if (btree_find_last(btree, item, iter) && !btree->multi)
return false;
btree_insert_at(iter, item);
return true;
}
bool btree_remove(struct btree *btree, const void *key)
{
btree_iterator iter;
bool success = false;
bool multi = btree->multi;
do {
if (btree_find_first(btree, key, iter)) {
btree_remove_at(iter);
success = true;
}
} while (multi);
return success;
}
void *btree_lookup(struct btree *btree, const void *key)
{
btree_iterator iter;
if (btree_find_first(btree, key, iter))
return iter->item;
return NULL;
}
int btree_begin_end_lr(const struct btree *btree, btree_iterator iter, int lr)
{
struct btree_node *node;
......@@ -374,6 +412,17 @@ int btree_cmp_iters(const btree_iterator iter_a, const btree_iterator iter_b)
return 0;
}
/********************* Built-in ordering functions *******************/
btree_search_implement
(
btree_strcmp,
char*,
int c = strcmp(a, b),
c == 0,
c < 0
)
/************************* Private functions *************************/
......
......@@ -33,10 +33,14 @@ Note: The following should work but are not well-tested yet:
btree_walk...
btree_cmp_iters
btree_insert
btree_remove
btree_lookup
*/
#include <stdbool.h>
#include <stdint.h>
#include <stddef.h>
#include <string.h>
/*
* Maximum number of items per node.
......@@ -90,6 +94,8 @@ typedef unsigned int btree_search_proto(
);
typedef btree_search_proto *btree_search_t;
btree_search_proto btree_strcmp;
/*
* Callback used by btree_delete() and btree_walk...().
*
......@@ -106,6 +112,7 @@ struct btree {
size_t count; /* Total number of items in B-tree */
btree_search_t search;
bool multi;
/*
* These are set to NULL by default.
......@@ -123,6 +130,30 @@ struct btree {
struct btree *btree_new(btree_search_t search);
void btree_delete(struct btree *btree);
/* Inserts an item into the btree. If an item already exists that is equal
* to this one (as determined by the search function), behavior depends on the
* btree->multi setting.
* If btree->multi is false (default), returns false, and no item
* is inserted (because it would be a duplicate).
* If btree->multi is true, returns true, putting the item after
* its duplicates.
*/
bool btree_insert(struct btree *btree, const void *item);
/* Removes an item from the btree. If an item exists that is equal to the
* key (as determined by the search function), it is removed.
*
* If btree->multi is set, all matching items are removed.
*
* Returns true if item was found and deleted, false if not found. */
bool btree_remove(struct btree *btree, const void *key);
/* Finds the requested item.
* Returns the item pointer on success, NULL on failure.
* Note that NULL is a valid item value. If you need to put
* NULLs in a btree, use btree_find instead. */
void *btree_lookup(struct btree *btree, const void *key);
/* lr must be 0 or 1, nothing else. */
int btree_begin_end_lr(const struct btree *btree, btree_iterator iter, int lr);
......
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