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text_buffer.rs
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text_buffer.rs
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use std::ops::Range;
/// Trait constraining what types [`crate::TextEdit`] may use as
/// an underlying buffer.
///
/// Most likely you will use a [`String`] which implements [`TextBuffer`].
pub trait TextBuffer {
/// Can this text be edited?
fn is_mutable(&self) -> bool;
/// Returns this buffer as a `str`.
fn as_str(&self) -> &str;
/// Reads the given character range.
fn char_range(&self, char_range: Range<usize>) -> &str {
assert!(char_range.start <= char_range.end);
let start_byte = self.byte_index_from_char_index(char_range.start);
let end_byte = self.byte_index_from_char_index(char_range.end);
&self.as_str()[start_byte..end_byte]
}
fn byte_index_from_char_index(&self, char_index: usize) -> usize {
byte_index_from_char_index(self.as_str(), char_index)
}
/// Inserts text `text` into this buffer at character index `char_index`.
///
/// # Notes
/// `char_index` is a *character index*, not a byte index.
///
/// # Return
/// Returns how many *characters* were successfully inserted
fn insert_text(&mut self, text: &str, char_index: usize) -> usize;
/// Deletes a range of text `char_range` from this buffer.
///
/// # Notes
/// `char_range` is a *character range*, not a byte range.
fn delete_char_range(&mut self, char_range: Range<usize>);
/// Clears all characters in this buffer
fn clear(&mut self) {
self.delete_char_range(0..self.as_str().len());
}
/// Replaces all contents of this string with `text`
fn replace(&mut self, text: &str) {
self.clear();
self.insert_text(text, 0);
}
/// Clears all characters in this buffer and returns a string of the contents.
fn take(&mut self) -> String {
let s = self.as_str().to_owned();
self.clear();
s
}
}
impl TextBuffer for String {
fn is_mutable(&self) -> bool {
true
}
fn as_str(&self) -> &str {
self.as_ref()
}
fn insert_text(&mut self, text: &str, char_index: usize) -> usize {
// Get the byte index from the character index
let byte_idx = self.byte_index_from_char_index(char_index);
// Then insert the string
self.insert_str(byte_idx, text);
text.chars().count()
}
fn delete_char_range(&mut self, char_range: Range<usize>) {
assert!(char_range.start <= char_range.end);
// Get both byte indices
let byte_start = self.byte_index_from_char_index(char_range.start);
let byte_end = self.byte_index_from_char_index(char_range.end);
// Then drain all characters within this range
self.drain(byte_start..byte_end);
}
fn clear(&mut self) {
self.clear();
}
fn replace(&mut self, text: &str) {
*self = text.to_owned();
}
fn take(&mut self) -> String {
std::mem::take(self)
}
}
/// Immutable view of a `&str`!
impl<'a> TextBuffer for &'a str {
fn is_mutable(&self) -> bool {
false
}
fn as_str(&self) -> &str {
self
}
fn insert_text(&mut self, _text: &str, _ch_idx: usize) -> usize {
0
}
fn delete_char_range(&mut self, _ch_range: Range<usize>) {}
}
fn byte_index_from_char_index(s: &str, char_index: usize) -> usize {
for (ci, (bi, _)) in s.char_indices().enumerate() {
if ci == char_index {
return bi;
}
}
s.len()
}