1Motivation 2========== 3 4Treaps provide a memory-efficient binary search tree structure. 5Insertion/deletion/search are about as about as fast in the average 6case as red-black trees and the chances of worst-case behavior are 7vanishingly small, thanks to (pseudo-)randomness. The bad worst-case 8behavior is a small price to pay, given that treaps are much simpler 9to implement. 10 11API 12=== 13 14The trp API generates a data structure and functions to handle a 15large growing set of objects stored in a pool. 16 17The caller: 18 19. Specifies parameters for the generated functions with the 20 trp_gen(static, foo_, ...) macro. 21 22. Allocates a `struct trp_root` variable and sets it to {~0}. 23 24. Adds new nodes to the set using `foo_insert`. 25 26. Can find a specific item in the set using `foo_search`. 27 28. Can iterate over items in the set using `foo_first` and `foo_next`. 29 30. Can remove an item from the set using `foo_remove`. 31 32Example: 33 34---- 35struct ex_node { 36 const char *s; 37 struct trp_node ex_link; 38}; 39static struct trp_root ex_base = {~0}; 40obj_pool_gen(ex, struct ex_node, 4096); 41trp_gen(static, ex_, struct ex_node, ex_link, ex, strcmp) 42struct ex_node *item; 43 44item = ex_pointer(ex_alloc(1)); 45item->s = "hello"; 46ex_insert(&ex_base, item); 47item = ex_pointer(ex_alloc(1)); 48item->s = "goodbye"; 49ex_insert(&ex_base, item); 50for (item = ex_first(&ex_base); item; item = ex_next(&ex_base, item)) 51 printf("%s\n", item->s); 52---- 53 54Functions 55--------- 56 57trp_gen(attr, foo_, node_type, link_field, pool, cmp):: 58 59 Generate a type-specific treap implementation. 60+ 61. The storage class for generated functions will be 'attr' (e.g., `static`). 62. Generated function names are prefixed with 'foo_' (e.g., `treap_`). 63. Treap nodes will be of type 'node_type' (e.g., `struct treap_node`). 64 This type must be a struct with at least one `struct trp_node` field 65 to point to its children. 66. The field used to access child nodes will be 'link_field'. 67. All treap nodes must lie in the 'pool' object pool. 68. Treap nodes must be totally ordered by the 'cmp' relation, with the 69 following prototype: 70+ 71int (*cmp)(node_type \*a, node_type \*b) 72+ 73and returning a value less than, equal to, or greater than zero 74according to the result of comparison. 75 76void foo_insert(struct trp_root *treap, node_type \*node):: 77 78 Insert node into treap. If inserted multiple times, 79 a node will appear in the treap multiple times. 80 81void foo_remove(struct trp_root *treap, node_type \*node):: 82 83 Remove node from treap. Caller must ensure node is 84 present in treap before using this function. 85 86node_type *foo_search(struct trp_root \*treap, node_type \*key):: 87 88 Search for a node that matches key. If no match is found, 89 result is NULL. 90 91node_type *foo_nsearch(struct trp_root \*treap, node_type \*key):: 92 93 Like `foo_search`, but if if the key is missing return what 94 would be key's successor, were key in treap (NULL if no 95 successor). 96 97node_type *foo_first(struct trp_root \*treap):: 98 99 Find the first item from the treap, in sorted order. 100 101node_type *foo_next(struct trp_root \*treap, node_type \*node):: 102 103 Find the next item.