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#![allow(clippy::cast_possible_wrap)]
use super::PlatformType;
use crate::error::ParseResult;
use crate::reader::{BinaryReader, Parse};
/// CMAP table data
/// Contains only the subset of the table needed for mapping unicode codepoints to glyph indices
#[derive(Debug, Default)]
pub struct CmapTable {
/// Mapping from glyph indices to unicode codepoints
pub mappings: Vec<u32>,
/// Raw Subtables
pub tables: Vec<CmapSubtable>,
}
impl CmapTable {
/// Returns the unicode codepoint for the given glyph index
#[must_use]
pub fn get_codepoint(&self, index: u16) -> Option<u32> {
if index as usize >= self.mappings.len() {
None
} else {
Some(self.mappings[index as usize])
}
}
}
impl Parse for CmapTable {
fn parse(reader: &mut BinaryReader) -> ParseResult<Self> {
let mut table = Self::default();
//
// Table header
reader.skip_u16()?; // version
let num_tables = reader.read_u16()?;
//
// Subtables
for _ in 0..num_tables {
let platform_id = reader.read_u16()?;
let encoding_id = reader.read_u16()?;
let offset = reader.read_u32()?;
debug_msg!(
" CMAP subtable: platform={}, encoding={}, offset={}",
platform_id,
encoding_id,
offset
);
let mut subtable_reader = reader.clone();
subtable_reader.advance_to(offset as usize)?;
let mut subtable = CmapSubtable::parse(&mut subtable_reader)?;
subtable.platform = platform_id.into();
subtable.encoding = encoding_id;
for (idx, cde) in &subtable.mappings {
let idx = *idx as usize;
if table.mappings.len() <= idx {
table.mappings.resize(idx + 1, 0xFFFF);
}
table.mappings[idx] = *cde;
}
table.tables.push(subtable);
}
Ok(table)
}
}
/// An individual CMAP subtable
#[derive(Debug, Default)]
pub struct CmapSubtable {
/// Platform ID
pub platform: PlatformType,
/// Encoding type
pub encoding: u16,
/// Mappings from glyph indices to unicode codepoints
pub mappings: Vec<(u16, u32)>,
}
impl Parse for CmapSubtable {
#[allow(clippy::too_many_lines)]
fn parse(reader: &mut BinaryReader) -> ParseResult<Self> {
let fmt = reader.read_u16()?;
let mut subtable = Self::default();
debug_msg!(" CMAP format: {}", fmt);
match fmt {
0 => {
//
// Format 0 CMAP tables are simple 1:1 mappings
reader.skip_u16()?; // length
reader.skip_u16()?; // language
for codepoint in 0u32..=0xFF {
let glyph_index = u16::from(reader.read_u8()?);
subtable.mappings.push((glyph_index, codepoint));
}
}
4 => {
//
// Format 4 CMAP tables are segmented mappings
reader.skip_u16()?; // length
reader.skip_u16()?; // language
let mut seg_count = reader.read_u16()?;
seg_count /= 2;
reader.skip_u16()?; // search range
reader.skip_u16()?; // entry selector
reader.skip_u16()?; // range shift
let mut end_code = Vec::with_capacity(seg_count as usize);
for _ in 0..seg_count {
end_code.push(reader.read_u16()?);
}
reader.skip_u16()?; // reserved pad
let mut start_code = Vec::with_capacity(seg_count as usize);
for _ in 0..seg_count {
start_code.push(reader.read_u16()?);
}
let mut id_delta = Vec::with_capacity(seg_count as usize);
for _ in 0..seg_count {
id_delta.push(reader.read_u16()?);
}
for i in 0..seg_count as usize {
let id_range_offset = reader.read_u16()?;
for codepoint in start_code[i]..=end_code[i] {
if codepoint == 0xFFFF {
subtable.mappings.push((0, 0xFFFF));
break;
}
let glyph_index = if id_range_offset == 0 {
//
// Simple mapping
codepoint.wrapping_add(id_delta[i])
} else {
//
// Indexed mapping
// let index_offset = id_range_offset / 2 + (codepoint - start_code[i]);
let index_offset =
id_range_offset + 2 * (codepoint - start_code[i]) - 2;
let mut glyph_reader = reader.clone();
glyph_reader.advance_by(index_offset as isize)?;
let glyph_index = glyph_reader.read_u16()?;
if glyph_index != 0 {
glyph_index.wrapping_add(id_delta[i])
} else {
glyph_index
}
};
subtable.mappings.push((glyph_index, u32::from(codepoint)));
}
}
}
6 => {
reader.skip_u16()?; // len
reader.skip_u16()?; // lang
let first_code = reader.read_u16()?;
let entry_count = reader.read_u16()?;
debug_msg!(
" CMAP format 6: first_code={}, entry_count={}",
first_code,
entry_count
);
for i in 0..u32::from(entry_count) {
let glyph_index = reader.read_u16()?;
let codepoint = u32::from(first_code) + i;
subtable.mappings.push((glyph_index, codepoint));
}
}
12 => {
//
// Format 12 CMAP tables are segmented mappings
reader.skip_u16()?; // reserved
reader.skip_u32()?; // len
reader.skip_u32()?; // lang
let num_groups = reader.read_u32()?;
debug_msg!(" CMAP format 12: num_groups={}", num_groups);
for _ in 0..num_groups {
let start = reader.read_u32()?;
let end = reader.read_u32()?;
let start_glyph = reader.read_u32()?; // Glyph index corresponding to the starting character code
debug_msg!(
" CMAP group: start={}, end={}, start_glyph={}",
start,
end,
start_glyph
);
let adj = if start < end { 1 } else { -1 };
let n = start.abs_diff(end);
let mut codepoint = start;
for i in 0..n {
let index = u16::try_from(start_glyph + i).unwrap_or_default();
subtable.mappings.push((index, codepoint));
codepoint = codepoint.wrapping_add_signed(adj);
}
}
}
_ => return Err(reader.err(&format!("Unsupported CMAP format: {fmt}"))),
}
debug_msg!(" Found {} mappings", subtable.mappings.len());
Ok(subtable)
}
}