PPATH(3) NetBSD Library Functions Manual PPATH(3)
NAME
ppath, ppath_idx, ppath_key, ppath_component_retain, ppath_component_release, ppath_create, ppath_length, ppath_component_idx, ppath_component_key, ppath_pop, ppath_push, ppath_component_at, ppath_subpath, ppath_push_idx, ppath_push_key, ppath_replace_idx, ppath_replace_key, ppath_copy, ppath_retain, ppath_release, ppath_lookup -- property container path library
LIBRARY
Property-List Paths Library (libppath, -lppath)
SYNOPSIS
#include <ppath/ppath.h> ppath_component_t * ppath_idx(unsigned int index); ppath_component_t * ppath_key(const char *key); ppath_component_t * ppath_component_retain(ppath_component_t *pc); void ppath_component_release(ppath_component_t *pc); ppath_t * ppath_create(void); unsigned int ppath_length(const ppath_t *p); int ppath_component_idx(const ppath_component_t *); const char * ppath_component_key(const ppath_component_t *); ppath_t * ppath_pop(ppath_t *, ppath_component_t **); ppath_t * ppath_push(ppath_t *, ppath_component_t *); ppath_component_t * ppath_component_at(const ppath_t *, unsigned int); ppath_t * ppath_subpath(const ppath_t *, unsigned int, unsigned int); ppath_t * ppath_push_idx(ppath_t *, unsigned int); ppath_t * ppath_push_key(ppath_t *, const char *); ppath_t * ppath_replace_idx(ppath_t *, unsigned int); ppath_t * ppath_replace_key(ppath_t *, const char *); ppath_t * ppath_copy(const ppath_t *); ppath_t * ppath_retain(ppath_t *); void ppath_release(ppath_t *); prop_object_t ppath_lookup(prop_object_t, const ppath_t *);
DESCRIPTION
The ppath library provides functions to read, write, or delete objects in a property list. A property-list ``path'' names the object in a property list to read, write, or delete. A property-list path is an ordered array of zero or more array indices and dictionary keys that names at most one prop_object_t in a property list. The abstract function E() evaluates a property-list path against a prop_object_t, o, to yield a prop_object_t result according to the fol- lowing recursive definition, where empty indicates the empty (zero-length) path and the operator ``|'' indicates the concatenation of the path on the left-hand side with the key or index on the right-hand side: E(o, empty) Evaluates to o. E(o, p | index) If E(o, p) evaluates to a prop_array_t, then E(o, p | index) evaluates to the index 'th element of that array. Otherwise, an error occurs. E(o, p | key) If E(o, p) evaluates to a prop_dictionary_t, then E(o, p | key) evaluates to the dictionary value stored under key. Otherwise, an error occurs. The programmer may think of property-list paths as working similarly to paths in a file system, where property arrays and dictionaries correspond to directories, and all other property types correspond to files.
DATA TYPES
ppath provides two opaque types: ppath_component_t A property-list path component: a single key or index. ppath counts references to a ppath_component_t and reclaims its storage when there are no more references. ppath_t An array of zero or more property-list path components. ppath counts references to a ppath_t and reclaims its storage when there are no more references.
FUNCTIONS
ppath provides these functions for manipulating property-list paths and their components: ppath_idx(unsigned int index) Allocate a new ppath_component_t for the given array index and return it. Its reference count is initially one. If there is not sufficient memory to complete the request, return NULL. ppath_key(const char *key) Allocate a new ppath_component_t for the given dictionary key and return it. Its reference count is initially one. If there is not sufficient memory to complete the request, return NULL. ppath_component_retain(ppath_component_t *pc) Increase the reference count on pc by one. ppath_component_release(ppath_component_t *pc) Decrease the reference count on pc by one. If the reference count reaches zero, reclaim the storage for pc. ppath_create(void) Create a new property-list path and return it. Its reference count is initially one. The path's length is initially zero. If there is not sufficient memory to complete the request, return NULL. ppath_length(const ppath_t *p) Return the number of components in path p. ppath_component_idx(const ppath_component_t *pc) Return the array index represented by the component pc, or -1 if pc does not represent an array index. ppath_component_key(const ppath_component_t *pc) Return the dictionary key represented by the component pc, or NULL if pc does not represent a dictionary key. ppath_pop(ppath_t *p, ppath_component_t **pcp) If p is the empty path or NULL, return NULL. Otherwise, remove the last component from p and return p, and if pcp is not NULL, write the removed component to *pcp. ppath_push(ppath_t *p, ppath_component_t *pc) If either p is NULL or no more components can be added to p, return NULL. Otherwise, append pc to the end of the component array p and return p. ppath_component_at(const ppath_t *p, unsigned int i) If either p is NULL or there is no ith component to p, return NULL. Otherwise, return the ith component of p. Before returning a component, ppath_component_at() increases its reference count. (The first component is 0.) ppath_subpath(const ppath_t *p, unsigned int first, unsigned int exclast) Create a new ppath_t and fill it with components first to exclast (exclusive) of p. If there are no such components as those in p, ppath_subpath() returns an empty ppath_t. If there is insuffi- cient memory to create the new path, or if p is NULL, return NULL. Otherwise, return the new path. ppath_push_idx(ppath_t *p, unsigned int idx) Append an array index, idx, to the end of path p. If p is NULL, or if there is insufficient memory to complete the operation, return NULL. Otherwise, return p. ppath_push_key(ppath_t *, const char *key) Append a dictionary key, key, to the end of path p. If p is NULL, or if there is insufficient memory to complete the operation, return NULL. Otherwise, return p. ppath_replace_idx(ppath_t *p, unsigned int idx) Replace the array index at the end of path p with the array index idx. If p is NULL, if the last component of p is not an array index, or if there is insufficient memory to complete the opera- tion, return NULL. Otherwise, return p. ppath_replace_key(ppath_t *p, const char *key) Replace the dictionary key at the end of path p with the dictio- nary key idx. If p is NULL, if the last component of p is not a dictionary key, or if there is insufficient memory to complete the operation, return NULL. Otherwise, return p. ppath_copy(const ppath_t *p) Create a copy of path p. If p is NULL, or if there is insuffi- cient memory to complete the operation, return NULL. Otherwise, return the copy, whose reference count will be one. ppath_retain(ppath_t *p) Increase the reference count on p and return p. ppath_release(ppath_t *p) Decrease the reference count on p. Reclaim the storage for p if the reference count reaches zero. ppath_lookup(prop_object_t o, const ppath_t *p) Return the prop_object_t under o named by p, or return NULL if no such prop_object_t is under o.
SEE ALSO
ppath_bool(3), ppath_number(3), ppath_object(3), proplib(3)
HISTORY
The ppath property container path library first appeared in NetBSD 6.0.
AUTHORS
David Young <dyoung@pobox.com> NetBSD 10.99 August 24, 2011 NetBSD 10.99
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