posts: gap-buffer: add construction

This commit is contained in:
Bruno BELANYI 2024-07-06 23:35:39 +01:00
parent 51a1bd01cd
commit a9f003f4ee

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@ -33,3 +33,42 @@ insertion at the cursor.
Moving the cursor moves the gap around the buffer, the prefix and suffix getting
shorter/longer as required.
## Implementation
I'll be writing a sample implementation in Python, as with the rest of the
[series]({{< ref "/series/cool-algorithms/">}}). I don't think it showcases the
elegance of the _Gap Buffer_ in action like a C implementation full of
`memmove`s would, but it does makes it short and sweet.
### Representation
We'll be representing the gap buffer as an actual list of characters.
Given that Python doesn't _have_ characters, let's settle for a list of strings,
each representing a single character...
```python
Char = str
class GapBuffer:
# List of characters, contains prefix and suffix of string with gap in the middle
_buf: list[Char]
# The gap is contained between [start, end) (i.e: buf[start:end])
_gap_start: int
_gap_end: int
# Visual representation of the gap buffer:
# This is a very [ ]long string.
# |<----------------------------------------------->| capacity
# |<------------>| |<-------->| string
# |<------------------->| gap
# |<------------>| prefix
# |<-------->| suffix
def __init__(self, initial_capacity: int = 16) -> None:
assert initial_capacity > 0
# Initialize an empty gap buffer
self._buf = [""] * initial_capacity
self._gap_start = 0
self._gap_end = initial_capacity
```