This introduces a Session class, which wraps libmongoc's client session object. Additionally, we support a "session" option on Manager and Server execute methods to allow operations to be associated with an explicit session (mostly relevant for causal consistency).
This makes WriteException a common base class of WriteConcernException and WriteErrorException. BulkWriteException, which may contain multiple write and/or write concern errors, will continue to inherit WriteException.
This class was not being used, since executeBulkWrite() uses BulkWriteException and the single write methods use WriteException and WriteConcernException exclusively.
Successive get_iterator handler invocations should throw a LogicException. This avoids situations that might allow the user to iterate over the same cursor multiple times.
libmongoc already provides a mechanism to upgrade a cursor with a single command result document into a command cursor, which will seamlessly iterate through the first batch and documents returned by successive getmore ops.
This allows us to remove our own "first batch" handling and simplify the move_forward and rewind iteration handlers.
This removes the invalidate_current handler. Due to SPL's implementation, our handler was being invoked between rewinding and checking if the current position was valid. Given that our validity check depends on inspecting a pointer to the current element (like MySQLi's result iterator), we cannot use invalidate_current.
The current element must still be freed during iteration, so we will instead call a php_phongo_cursor_free_current() function as needed. Additionally, we should track a reference to the Cursor object zval on the iterator itself, which will ensure it is not garbage-collected during iteration (demonstrated in the segfault backtrace in PHPC-215).
Lastly, this commit renames the Cursor object and iterator structs and related functions to be more consistent with implementions in PHP core.
Jeremy Mikola