libplist API does not offer a way to clone or modify nodes

Attempted to implement lockdown's get/set/remove value request and came up with those signatures:

iphone_error_t lockdownd_get_value(lockdownd_client_t client, char domain, char key, plist_t value);
iphone_error_t lockdownd_set_value(lockdownd_client_t client, char domain, char key, plist_t value);
iphone_error_t lockdownd_remove_value(lockdownd_client_t client, char domain, char *key);

For instance lockdownd_get_value() returns the value plist subnode for the key named "Value". The issue here was that there is no way in libplist to copy/clone an existing node. This also becomes a problem for set_value(), which actually has to clone the passed value node to construct a lockdown request plist with the value node attached to send to lockdownd.

The intermediate solution was to use plist_to_bin() to serialize the plist subnode into a buffer, then use plist_from_bin() to unserialize the plist into a node again effectively ending up with a cloned node.

Also while thinking about implementing a plist GUI editor similar to the one on Mac OS X, libplist should also provide the necessary functions to deal with modifications of node trees.

I think the missing operations are:

• clone nodes (recurse deep copy) - needed to fix this bug
• modify node values (e.g.: for quick, plist load -> change <string> value, save modified plist)
• remove nodes (Does plist_free() also unlink the "destroyed" node from the parent tree?)

Another question is how far this functionality should make sure the strict "<key /><VALUE />" node structure is not compromised or whether allow the "freedom" to work on individual nodes.

Simple idea:

// Return a copy of passed node and it's children
PLIST_API plist_t plist_copy(plist_t node);
// modify value of a node
PLIST_API void plist_set_key_val(plist_t node, char val);
PLIST_API void plist_set_string_val(plist_t node, char val);
PLIST_API void plist_set_bool_val(plist_t node, uint8_t val);
PLIST_API void plist_set_uint_val(plist_t node, uint64_t val);
PLIST_API void plist_set_real_val(plist_t node, double val);
PLIST_API void plist_set_data_val(plist_t node, char *val, uint64_t length);
PLIST_API void plist_set_date_val(plist_t node, int32_t sec, int32_t usec);