fix: ensure_grapheme_boundary_next_byte needs to index at valid char

This commit is contained in:
Blaž Hrastnik 2022-01-14 12:13:53 +09:00
parent add3be8528
commit 2302869836

View File

@ -203,7 +203,12 @@ pub fn ensure_grapheme_boundary_next_byte(slice: RopeSlice, byte_idx: usize) ->
if byte_idx == 0 {
byte_idx
} else {
next_grapheme_boundary_byte(slice, byte_idx - 1)
// TODO: optimize so we're not constructing grapheme cursor twice
if is_grapheme_boundary_byte(slice, byte_idx) {
byte_idx
} else {
next_grapheme_boundary_byte(slice, byte_idx)
}
}
}
@ -235,6 +240,31 @@ pub fn is_grapheme_boundary(slice: RopeSlice, char_idx: usize) -> bool {
}
}
/// Returns whether the given byte position is a grapheme boundary.
#[must_use]
pub fn is_grapheme_boundary_byte(slice: RopeSlice, byte_idx: usize) -> bool {
// Bounds check
debug_assert!(byte_idx <= slice.len_bytes());
// Get the chunk with our byte index in it.
let (chunk, chunk_byte_idx, _, _) = slice.chunk_at_byte(byte_idx);
// Set up the grapheme cursor.
let mut gc = GraphemeCursor::new(byte_idx, slice.len_bytes(), true);
// Determine if the given position is a grapheme cluster boundary.
loop {
match gc.is_boundary(chunk, chunk_byte_idx) {
Ok(n) => return n,
Err(GraphemeIncomplete::PreContext(n)) => {
let (ctx_chunk, ctx_byte_start, _, _) = slice.chunk_at_byte(n - 1);
gc.provide_context(ctx_chunk, ctx_byte_start);
}
Err(_) => unreachable!(),
}
}
}
/// An iterator over the graphemes of a `RopeSlice`.
#[derive(Clone)]
pub struct RopeGraphemes<'a> {