Emmanuel Lécharny wrote:
Hi,
some thoughts about the current implementation :
Cursor support in Mavibot
-------------------------
The current implementation is a bit unsastifactory, and it does not
necessarily fits with the simplifications we are introducing (namely,
the removal of duplicate values). Typically, the current cursor allows
the user to move forward and backward across keys and values, when we
only need to move across keys now.
Moving
------
First of all, we must be able to move backward and forward. Fetching an
element is a different operation than moving, but one should still be
able to get back an element when moving. This is done through 4 methods,
2 which are relative, and 2 which are absolute.
Relative moves :
next() : move forward to the net key
prev() : move forward to the net key
Absolute moves :
next(K) : move after the given key
prev(K) : move before the given key
These absolute moves seem like an extravagance. I have never seen a dbm-style
library with such methods. It's more natural to have an explicit seek() method
and then do a relative next/prev after that.
For reference, in BerkeleyDB, there is cursor_first/last. Also, on a freshly
created cursor, next() == first() and prev() == last(). That is, the
first/last methods aren't even needed on a fresh cursor.
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