posts: gap-buffer: add movement

This commit is contained in:
Bruno BELANYI 2024-07-06 23:41:31 +01:00
parent bbdb14bad8
commit 01aafd372b

View file

@ -159,3 +159,33 @@ def delete(self, dist: int = 1) -> None:
# Extend gap to the right
self._gap_end += dist
```
### Moving the cursor
Moving the cursor along the buffer will shift letters from one side of the gap
to the other, moving them accross from prefix to suffix and back.
I find Python's list slicing not quite as elegant to read as a `memmove`, though
it does make for a very small and efficient implementation.
```python
def left(self, dist: int = 1) -> None:
assert dist <= self.prefix_length
# Shift the needed number of characters from end of prefix to start of suffix
self._buf[self._gap_end - dist : self._gap_end] = self._buf[
self._gap_start - dist : self._gap_start
]
# Adjust indices accordingly
self._gap_start -= dist
self._gap_end -= dist
def right(self, dist: int = 1) -> None:
assert dist <= self.suffix_length
# Shift the needed number of characters from start of suffix to end of prefix
self._buf[self._gap_start : self._gap_start + dist] = self._buf[
self._gap_end : self._gap_end + dist
]
# Adjust indices accordingly
self._gap_start += dist
self._gap_end += dist
```