1use core::convert::TryFrom;
2
3use crate::parser::{LazyArray16, Stream};
4use crate::GlyphId;
5
6/// A [format 6](https://docs.microsoft.com/en-us/typography/opentype/spec/cmap#format-6-trimmed-table-mapping)
7/// subtable.
8#[derive(Clone, Copy, Debug)]
9pub struct Subtable6<'a> {
10 /// First character code of subrange.
11 pub first_code_point: u16,
12 /// Array of glyph indexes for character codes in the range.
13 pub glyphs: LazyArray16<'a, GlyphId>,
14}
15
16impl<'a> Subtable6<'a> {
17 /// Parses a subtable from raw data.
18 pub fn parse(data: &'a [u8]) -> Option<Self> {
19 let mut s = Stream::new(data);
20 s.skip::<u16>(); // format
21 s.skip::<u16>(); // length
22 s.skip::<u16>(); // language
23 let first_code_point = s.read::<u16>()?;
24 let count = s.read::<u16>()?;
25 let glyphs = s.read_array16::<GlyphId>(count)?;
26 Some(Self {
27 first_code_point,
28 glyphs,
29 })
30 }
31
32 /// Returns a glyph index for a code point.
33 ///
34 /// Returns `None` when `code_point` is larger than `u16`.
35 pub fn glyph_index(&self, code_point: u32) -> Option<GlyphId> {
36 // This subtable supports code points only in a u16 range.
37 let code_point = u16::try_from(code_point).ok()?;
38 let idx = code_point.checked_sub(self.first_code_point)?;
39 self.glyphs.get(idx)
40 }
41
42 /// Calls `f` for each codepoint defined in this table.
43 pub fn codepoints(&self, mut f: impl FnMut(u32)) {
44 for i in 0..self.glyphs.len() {
45 if let Some(code_point) = self.first_code_point.checked_add(i) {
46 f(u32::from(code_point));
47 }
48 }
49 }
50}
51