You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
109 lines
3.3 KiB
109 lines
3.3 KiB
Motivation |
|
========== |
|
|
|
Treaps provide a memory-efficient binary search tree structure. |
|
Insertion/deletion/search are about as about as fast in the average |
|
case as red-black trees and the chances of worst-case behavior are |
|
vanishingly small, thanks to (pseudo-)randomness. The bad worst-case |
|
behavior is a small price to pay, given that treaps are much simpler |
|
to implement. |
|
|
|
API |
|
=== |
|
|
|
The trp API generates a data structure and functions to handle a |
|
large growing set of objects stored in a pool. |
|
|
|
The caller: |
|
|
|
. Specifies parameters for the generated functions with the |
|
trp_gen(static, foo_, ...) macro. |
|
|
|
. Allocates a `struct trp_root` variable and sets it to {~0}. |
|
|
|
. Adds new nodes to the set using `foo_insert`. Any pointers |
|
to existing nodes cannot be relied upon any more, so the caller |
|
might retrieve them anew with `foo_pointer`. |
|
|
|
. Can find a specific item in the set using `foo_search`. |
|
|
|
. Can iterate over items in the set using `foo_first` and `foo_next`. |
|
|
|
. Can remove an item from the set using `foo_remove`. |
|
|
|
Example: |
|
|
|
---- |
|
struct ex_node { |
|
const char *s; |
|
struct trp_node ex_link; |
|
}; |
|
static struct trp_root ex_base = {~0}; |
|
obj_pool_gen(ex, struct ex_node, 4096); |
|
trp_gen(static, ex_, struct ex_node, ex_link, ex, strcmp) |
|
struct ex_node *item; |
|
|
|
item = ex_pointer(ex_alloc(1)); |
|
item->s = "hello"; |
|
ex_insert(&ex_base, item); |
|
item = ex_pointer(ex_alloc(1)); |
|
item->s = "goodbye"; |
|
ex_insert(&ex_base, item); |
|
for (item = ex_first(&ex_base); item; item = ex_next(&ex_base, item)) |
|
printf("%s\n", item->s); |
|
---- |
|
|
|
Functions |
|
--------- |
|
|
|
trp_gen(attr, foo_, node_type, link_field, pool, cmp):: |
|
|
|
Generate a type-specific treap implementation. |
|
+ |
|
. The storage class for generated functions will be 'attr' (e.g., `static`). |
|
. Generated function names are prefixed with 'foo_' (e.g., `treap_`). |
|
. Treap nodes will be of type 'node_type' (e.g., `struct treap_node`). |
|
This type must be a struct with at least one `struct trp_node` field |
|
to point to its children. |
|
. The field used to access child nodes will be 'link_field'. |
|
. All treap nodes must lie in the 'pool' object pool. |
|
. Treap nodes must be totally ordered by the 'cmp' relation, with the |
|
following prototype: |
|
+ |
|
int (*cmp)(node_type \*a, node_type \*b) |
|
+ |
|
and returning a value less than, equal to, or greater than zero |
|
according to the result of comparison. |
|
|
|
node_type {asterisk}foo_insert(struct trp_root *treap, node_type \*node):: |
|
|
|
Insert node into treap. If inserted multiple times, |
|
a node will appear in the treap multiple times. |
|
+ |
|
The return value is the address of the node within the treap, |
|
which might differ from `node` if `pool_alloc` had to call |
|
`realloc` to expand the pool. |
|
|
|
void foo_remove(struct trp_root *treap, node_type \*node):: |
|
|
|
Remove node from treap. Caller must ensure node is |
|
present in treap before using this function. |
|
|
|
node_type *foo_search(struct trp_root \*treap, node_type \*key):: |
|
|
|
Search for a node that matches key. If no match is found, |
|
result is NULL. |
|
|
|
node_type *foo_nsearch(struct trp_root \*treap, node_type \*key):: |
|
|
|
Like `foo_search`, but if the key is missing return what |
|
would be key's successor, were key in treap (NULL if no |
|
successor). |
|
|
|
node_type *foo_first(struct trp_root \*treap):: |
|
|
|
Find the first item from the treap, in sorted order. |
|
|
|
node_type *foo_next(struct trp_root \*treap, node_type \*node):: |
|
|
|
Find the next item.
|
|
|