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use core::convert::TryFrom;
use crate::{GlyphId, NormalizedCoord};
use crate::parser::{Stream, Offset, Offset32};
use crate::var_store::ItemVariationStore;
#[derive(Clone, Copy)]
pub struct Table<'a> {
data: &'a [u8],
variation_store: ItemVariationStore<'a>,
advance_width_mapping_offset: Option<Offset32>,
lsb_mapping_offset: Option<Offset32>,
}
impl<'a> Table<'a> {
pub fn parse(data: &'a [u8]) -> Option<Self> {
let mut s = Stream::new(data);
let version: u32 = s.read()?;
if version != 0x00010000 {
return None;
}
let variation_store_offset: Offset32 = s.read()?;
let var_store_s = Stream::new_at(data, variation_store_offset.to_usize())?;
let variation_store = ItemVariationStore::parse(var_store_s)?;
Some(Table {
data,
variation_store,
advance_width_mapping_offset: s.read()?,
lsb_mapping_offset: s.read()?,
})
}
}
pub struct DeltaSetIndexMap<'a> {
data: &'a [u8],
}
impl<'a> DeltaSetIndexMap<'a> {
#[inline]
pub fn new(data: &'a [u8]) -> Self {
DeltaSetIndexMap { data }
}
#[inline]
pub fn map(&self, glyph_id: GlyphId) -> Option<(u16, u16)> {
let mut idx = glyph_id.0;
let mut s = Stream::new(self.data);
let entry_format: u16 = s.read()?;
let map_count: u16 = s.read()?;
if map_count == 0 {
return None;
}
if idx >= map_count {
idx = map_count - 1;
}
let entry_size = ((entry_format >> 4) & 3) + 1;
let inner_index_bit_count = u32::from((entry_format & 0xF) + 1);
s.advance(usize::from(entry_size) * usize::from(idx));
let mut n = 0u32;
for b in s.read_bytes(usize::from(entry_size))? {
n = (n << 8) + u32::from(*b);
}
let outer_index = n >> inner_index_bit_count;
let inner_index = n & ((1 << inner_index_bit_count) - 1);
Some((
u16::try_from(outer_index).ok()?,
u16::try_from(inner_index).ok()?
))
}
}
#[inline]
pub(crate) fn glyph_advance_offset(
table: Table,
glyph_id: GlyphId,
coordinates: &[NormalizedCoord],
) -> Option<f32> {
let (outer_idx, inner_idx) = if let Some(offset) = table.advance_width_mapping_offset {
DeltaSetIndexMap::new(table.data.get(offset.to_usize()..)?).map(glyph_id)?
} else {
(0, glyph_id.0)
};
table.variation_store.parse_delta(outer_idx, inner_idx, coordinates)
}
#[inline]
pub(crate) fn glyph_side_bearing_offset(
table: Table,
glyph_id: GlyphId,
coordinates: &[NormalizedCoord],
) -> Option<f32> {
let set_data = table.data.get(table.lsb_mapping_offset?.to_usize()..)?;
let (outer_idx, inner_idx) = DeltaSetIndexMap::new(set_data).map(glyph_id)?;
table.variation_store.parse_delta(outer_idx, inner_idx, coordinates)
}