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author | Jason Evans <jasone@canonware.com> | 2010-08-09 17:17:34 -0500 |
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committer | Junio C Hamano <gitster@pobox.com> | 2010-08-14 19:35:37 -0700 |
commit | 951f316470acc7c785c460a4e40735b22822349f (patch) | |
tree | 8cc846b9eead64502e00fc4064d5decfa1897320 /vcs-svn/trp.txt | |
parent | 4709455db3891f6cad9a96a574296b4926f70cbe (diff) | |
download | git-951f316470acc7c785c460a4e40735b22822349f.tar.gz |
Add treap implementation
Provide macros to generate a type-specific treap implementation and
various functions to operate on it. It uses obj_pool.h to store memory
nodes in a treap. Previously committed nodes are never removed from
the pool; after any *_commit operation, it is assumed (correctly, in
the case of svn-fast-export) that someone else must care about them.
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.
>From http://www.canonware.com/download/trp/trp_hash/trp.h
[db: Altered to reference nodes by offset from a common base pointer]
[db: Bob Jenkins' hashing implementation dropped for Knuth's]
[db: Methods unnecessary for search and insert dropped]
[rr: Squelched compiler warnings]
[db: Added support for immutable treap nodes]
[jn: Reintroduced treap_nsearch(); with tests]
Signed-off-by: David Barr <david.barr@cordelta.com>
Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'vcs-svn/trp.txt')
-rw-r--r-- | vcs-svn/trp.txt | 103 |
1 files changed, 103 insertions, 0 deletions
diff --git a/vcs-svn/trp.txt b/vcs-svn/trp.txt new file mode 100644 index 0000000000..eb4c191875 --- /dev/null +++ b/vcs-svn/trp.txt @@ -0,0 +1,103 @@ +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`. + +. 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. + +void 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. + +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 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. |