Find the first position of any entries matching a prefix. To find the first
position of a path inside a given folder, suffix the prefix with a '/'.
@param at_pos the address to which the position of the index entry is written
(optional)
@param index an existing index object
@param prefix the prefix to search for
@return 0 with valid value in at_pos; an error code otherwise
Find the first position of any entries matching a prefix. To find the first position of a path inside a given folder, suffix the prefix with a '/'.
@param at_pos the address to which the position of the index entry is written (optional) @param index an existing index object @param prefix the prefix to search for @return 0 with valid value in at_pos; an error code otherwise