cp_narytree

Section: libcprops - cp_narytree (3)
Updated: SEPTEMBER 2006
Index Return to Main Contents

NAME

cp_narytree_lock, cp_narytree_rdlock, cp_narytree_wrlock, cp_narytree_unlock - acquire / release a lock on an N-ary tree

SYNOPSIS

#include <cprops/nary.h>

int cp_narytree_lock(cp_narytree *tree, int type);
int cp_narytree_rdlock(cp_narytree *tree);
int cp_narytree_wrlock(cp_narytree *tree);
int cp_narytree_unlock(cp_narytree *tree);

cp_narytree_lock

locks the tree for reading if type is COLLECTION_LOCK_READ or for writing if type is COLLECTION_LOCK_WRITE. The tree mode may not have COLLECTION_MODE_NOSYNC set prior to locking. Explicit locking isn't required for single tree operations (insertion, retrieval, deletion) which perform locking on their own but rather for transaction-like operations. To prevent other threads from accessing the tree while performing a series of mapping insertion, removal and lookup operations, the tree must be explicitly locked first. Tree operation functions will not attempt locking if the current thread owns the tree lock. This prevents deadlocks but leaves the responsibility for using the correct kind of locking with the application: if there's any possibility the application could change the tree structure in the transaction (ie insert or remove a mapping), the tree must be write locked. If the transaction consists of lookups only, the tree may be read locked.

Calls to cp_narytree_lock must be coupled with calls to cp_narytree_unlock after the operation is completed.

cp_narytree_rdlock(tree) is a synonym for cp_narytree_lock(tree, COLLECTION_LOCK_READ).

is a synonym for cp_narytree_lock(tree, COLLECTION_LOCK_WRITE).

RETURN VALUE

cp_narytree_lock, cp_narytree_rdlock and cp_narytree_wrlock return 0 on success, EINVAL if COLLECTION_MODE_NOSYNC is set or -1 if locking fails.
cp_narytree_unlock returns 0 on success or -1 if unlocking fails.