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103 lines
3.0 KiB
103 lines
3.0 KiB
Motivation |
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========== |
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Treaps provide a memory-efficient binary search tree structure. |
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Insertion/deletion/search are about as about as fast in the average |
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case as red-black trees and the chances of worst-case behavior are |
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vanishingly small, thanks to (pseudo-)randomness. The bad worst-case |
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behavior is a small price to pay, given that treaps are much simpler |
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to implement. |
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API |
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=== |
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The trp API generates a data structure and functions to handle a |
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large growing set of objects stored in a pool. |
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The caller: |
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. Specifies parameters for the generated functions with the |
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trp_gen(static, foo_, ...) macro. |
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. Allocates a `struct trp_root` variable and sets it to {~0}. |
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. Adds new nodes to the set using `foo_insert`. |
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. Can find a specific item in the set using `foo_search`. |
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. Can iterate over items in the set using `foo_first` and `foo_next`. |
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. Can remove an item from the set using `foo_remove`. |
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Example: |
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---- |
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struct ex_node { |
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const char *s; |
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struct trp_node ex_link; |
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}; |
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static struct trp_root ex_base = {~0}; |
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obj_pool_gen(ex, struct ex_node, 4096); |
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trp_gen(static, ex_, struct ex_node, ex_link, ex, strcmp) |
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struct ex_node *item; |
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item = ex_pointer(ex_alloc(1)); |
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item->s = "hello"; |
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ex_insert(&ex_base, item); |
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item = ex_pointer(ex_alloc(1)); |
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item->s = "goodbye"; |
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ex_insert(&ex_base, item); |
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for (item = ex_first(&ex_base); item; item = ex_next(&ex_base, item)) |
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printf("%s\n", item->s); |
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---- |
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Functions |
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--------- |
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trp_gen(attr, foo_, node_type, link_field, pool, cmp):: |
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Generate a type-specific treap implementation. |
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+ |
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. The storage class for generated functions will be 'attr' (e.g., `static`). |
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. Generated function names are prefixed with 'foo_' (e.g., `treap_`). |
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. Treap nodes will be of type 'node_type' (e.g., `struct treap_node`). |
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This type must be a struct with at least one `struct trp_node` field |
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to point to its children. |
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. The field used to access child nodes will be 'link_field'. |
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. All treap nodes must lie in the 'pool' object pool. |
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. Treap nodes must be totally ordered by the 'cmp' relation, with the |
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following prototype: |
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+ |
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int (*cmp)(node_type \*a, node_type \*b) |
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+ |
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and returning a value less than, equal to, or greater than zero |
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according to the result of comparison. |
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void foo_insert(struct trp_root *treap, node_type \*node):: |
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Insert node into treap. If inserted multiple times, |
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a node will appear in the treap multiple times. |
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void foo_remove(struct trp_root *treap, node_type \*node):: |
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Remove node from treap. Caller must ensure node is |
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present in treap before using this function. |
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node_type *foo_search(struct trp_root \*treap, node_type \*key):: |
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Search for a node that matches key. If no match is found, |
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result is NULL. |
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node_type *foo_nsearch(struct trp_root \*treap, node_type \*key):: |
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Like `foo_search`, but if if the key is missing return what |
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would be key's successor, were key in treap (NULL if no |
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successor). |
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node_type *foo_first(struct trp_root \*treap):: |
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Find the first item from the treap, in sorted order. |
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node_type *foo_next(struct trp_root \*treap, node_type \*node):: |
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Find the next item.
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