Fix outofbounds of get_errmsg() and use it in cast functions
Fix typo in basic_operation.hpp
Add an example script getting a google top page
utimens: do not throw an unneeded exception
fs_root: get_entry_of(): return null if a parent dir not found
dns_op: throw exception with gai_strerror() if an error occurred
fs_core.cpp: find file_entry from its parent dir
file,dir cast: throw an exception if given entry is null
operation_layer: separate definition from decl
Fix trivial coding styles
fs_core: use returned entry avoiding searching cost
planet/common: change error messages
Handle errors occurred in read,write operations
planet_getattr: return result of fs_root.getattr()
Add utilities for searching fs entries
Update examples
utils: consider the case that an entry is null
handle: clean up
Makefile: disable multi-thread support / add warnings