1//! A [Compact Font Format 2 Table](
2//! https://docs.microsoft.com/en-us/typography/opentype/spec/cff2) implementation.
3
4// https://docs.microsoft.com/en-us/typography/opentype/spec/cff2charstr
5
6use core::convert::TryFrom;
7use core::ops::Range;
8
9use super::argstack::ArgumentsStack;
10use super::charstring::CharStringParser;
11use super::dict::DictionaryParser;
12use super::index::{parse_index, Index};
13use super::{calc_subroutine_bias, conv_subroutine_index, Builder, CFFError};
14use crate::parser::{NumFrom, Stream, TryNumFrom};
15use crate::var_store::*;
16use crate::{GlyphId, NormalizedCoordinate, OutlineBuilder, Rect, RectF};
17
18// https://docs.microsoft.com/en-us/typography/opentype/spec/cff2#7-top-dict-data
19// 'Operators in DICT may be preceded by up to a maximum of 513 operands.'
20const MAX_OPERANDS_LEN: usize = 513;
21
22// https://docs.microsoft.com/en-us/typography/opentype/spec/cff2charstr#appendix-b-cff2-charstring-implementation-limits
23const STACK_LIMIT: u8 = 10;
24const MAX_ARGUMENTS_STACK_LEN: usize = 513;
25
26const TWO_BYTE_OPERATOR_MARK: u8 = 12;
27
28// https://docs.microsoft.com/en-us/typography/opentype/spec/cff2charstr#4-charstring-operators
29mod operator {
30 pub const HORIZONTAL_STEM: u8 = 1;
31 pub const VERTICAL_STEM: u8 = 3;
32 pub const VERTICAL_MOVE_TO: u8 = 4;
33 pub const LINE_TO: u8 = 5;
34 pub const HORIZONTAL_LINE_TO: u8 = 6;
35 pub const VERTICAL_LINE_TO: u8 = 7;
36 pub const CURVE_TO: u8 = 8;
37 pub const CALL_LOCAL_SUBROUTINE: u8 = 10;
38 pub const VS_INDEX: u8 = 15;
39 pub const BLEND: u8 = 16;
40 pub const HORIZONTAL_STEM_HINT_MASK: u8 = 18;
41 pub const HINT_MASK: u8 = 19;
42 pub const COUNTER_MASK: u8 = 20;
43 pub const MOVE_TO: u8 = 21;
44 pub const HORIZONTAL_MOVE_TO: u8 = 22;
45 pub const VERTICAL_STEM_HINT_MASK: u8 = 23;
46 pub const CURVE_LINE: u8 = 24;
47 pub const LINE_CURVE: u8 = 25;
48 pub const VV_CURVE_TO: u8 = 26;
49 pub const HH_CURVE_TO: u8 = 27;
50 pub const SHORT_INT: u8 = 28;
51 pub const CALL_GLOBAL_SUBROUTINE: u8 = 29;
52 pub const VH_CURVE_TO: u8 = 30;
53 pub const HV_CURVE_TO: u8 = 31;
54 pub const HFLEX: u8 = 34;
55 pub const FLEX: u8 = 35;
56 pub const HFLEX1: u8 = 36;
57 pub const FLEX1: u8 = 37;
58 pub const FIXED_16_16: u8 = 255;
59}
60
61// https://docs.microsoft.com/en-us/typography/opentype/spec/cff2#table-9-top-dict-operator-entries
62mod top_dict_operator {
63 pub const CHAR_STRINGS_OFFSET: u16 = 17;
64 pub const VARIATION_STORE_OFFSET: u16 = 24;
65 pub const FONT_DICT_INDEX_OFFSET: u16 = 1236;
66}
67
68// https://docs.microsoft.com/en-us/typography/opentype/spec/cff2#table-10-font-dict-operator-entries
69mod font_dict_operator {
70 pub const PRIVATE_DICT_SIZE_AND_OFFSET: u16 = 18;
71}
72
73// https://docs.microsoft.com/en-us/typography/opentype/spec/cff2#table-16-private-dict-operators
74mod private_dict_operator {
75 pub const LOCAL_SUBROUTINES_OFFSET: u16 = 19;
76}
77
78#[derive(Clone, Copy, Default)]
79struct TopDictData {
80 char_strings_offset: usize,
81 font_dict_index_offset: Option<usize>,
82 variation_store_offset: Option<usize>,
83}
84
85fn parse_top_dict(data: &[u8]) -> Option<TopDictData> {
86 let mut dict_data: TopDictData = TopDictData::default();
87
88 let mut operands_buffer: [f64; 513] = [0.0; MAX_OPERANDS_LEN];
89 let mut dict_parser: DictionaryParser<'_> = DictionaryParser::new(data, &mut operands_buffer);
90 while let Some(operator: Operator) = dict_parser.parse_next() {
91 if operator.get() == top_dict_operator::CHAR_STRINGS_OFFSET {
92 dict_data.char_strings_offset = dict_parser.parse_offset()?;
93 } else if operator.get() == top_dict_operator::FONT_DICT_INDEX_OFFSET {
94 dict_data.font_dict_index_offset = dict_parser.parse_offset();
95 } else if operator.get() == top_dict_operator::VARIATION_STORE_OFFSET {
96 dict_data.variation_store_offset = dict_parser.parse_offset();
97 }
98 }
99
100 // Must be set, otherwise there are nothing to parse.
101 if dict_data.char_strings_offset == 0 {
102 return None;
103 }
104
105 Some(dict_data)
106}
107
108fn parse_font_dict(data: &[u8]) -> Option<Range<usize>> {
109 let mut private_dict_range: Option> = None;
110
111 let mut operands_buffer: [f64; 513] = [0.0; MAX_OPERANDS_LEN];
112 let mut dict_parser: DictionaryParser<'_> = DictionaryParser::new(data, &mut operands_buffer);
113 while let Some(operator: Operator) = dict_parser.parse_next() {
114 if operator.get() == font_dict_operator::PRIVATE_DICT_SIZE_AND_OFFSET {
115 dict_parser.parse_operands()?;
116 let operands: &[f64] = dict_parser.operands();
117
118 if operands.len() == 2 {
119 let len: usize = usize::try_from(operands[0] as i32).ok()?;
120 let start: usize = usize::try_from(operands[1] as i32).ok()?;
121 let end: usize = start.checked_add(len)?;
122 private_dict_range = Some(start..end);
123 }
124
125 break;
126 }
127 }
128
129 private_dict_range
130}
131
132fn parse_private_dict(data: &[u8]) -> Option<usize> {
133 let mut subroutines_offset: Option = None;
134 let mut operands_buffer: [f64; 513] = [0.0; MAX_OPERANDS_LEN];
135 let mut dict_parser: DictionaryParser<'_> = DictionaryParser::new(data, &mut operands_buffer);
136 while let Some(operator: Operator) = dict_parser.parse_next() {
137 if operator.get() == private_dict_operator::LOCAL_SUBROUTINES_OFFSET {
138 dict_parser.parse_operands()?;
139 let operands: &[f64] = dict_parser.operands();
140
141 if operands.len() == 1 {
142 subroutines_offset = usize::try_from(operands[0] as i32).ok();
143 }
144
145 break;
146 }
147 }
148
149 subroutines_offset
150}
151
152/// CFF2 allows up to 65535 scalars, but an average font will have 3-5.
153/// So 64 is more than enough.
154const SCALARS_MAX: u8 = 64;
155
156#[derive(Clone, Copy)]
157pub(crate) struct Scalars {
158 d: [f32; SCALARS_MAX as usize], // 256B
159 len: u8,
160}
161
162impl Default for Scalars {
163 fn default() -> Self {
164 Scalars {
165 d: [0.0; SCALARS_MAX as usize],
166 len: 0,
167 }
168 }
169}
170
171impl Scalars {
172 pub fn len(&self) -> u8 {
173 self.len
174 }
175
176 pub fn clear(&mut self) {
177 self.len = 0;
178 }
179
180 pub fn at(&self, i: u8) -> f32 {
181 if i < self.len {
182 self.d[usize::from(i)]
183 } else {
184 0.0
185 }
186 }
187
188 pub fn push(&mut self, n: f32) -> Option<()> {
189 if self.len < SCALARS_MAX {
190 self.d[usize::from(self.len)] = n;
191 self.len += 1;
192 Some(())
193 } else {
194 None
195 }
196 }
197}
198
199struct CharStringParserContext<'a> {
200 metadata: &'a Table<'a>,
201 coordinates: &'a [NormalizedCoordinate],
202 scalars: Scalars,
203 had_vsindex: bool,
204 had_blend: bool,
205 stems_len: u32,
206}
207
208impl CharStringParserContext<'_> {
209 fn update_scalars(&mut self, index: u16) -> Result<(), CFFError> {
210 self.scalars.clear();
211
212 let indices: LazyArray16<'_, u16> = self
213 .metadata
214 .item_variation_store
215 .region_indices(index)
216 .ok_or(err:CFFError::InvalidItemVariationDataIndex)?;
217 for index: u16 in indices {
218 let scalar: f32 = self
219 .metadata
220 .item_variation_store
221 .regions
222 .evaluate_region(index, self.coordinates);
223 self.scalars
224 .push(scalar)
225 .ok_or(err:CFFError::BlendRegionsLimitReached)?;
226 }
227
228 Ok(())
229 }
230}
231
232fn parse_char_string(
233 data: &[u8],
234 metadata: &Table,
235 coordinates: &[NormalizedCoordinate],
236 builder: &mut dyn OutlineBuilder,
237) -> Result<Rect, CFFError> {
238 let mut ctx = CharStringParserContext {
239 metadata,
240 coordinates,
241 scalars: Scalars::default(),
242 had_vsindex: false,
243 had_blend: false,
244 stems_len: 0,
245 };
246
247 // Load scalars at default index.
248 ctx.update_scalars(0)?;
249
250 let mut inner_builder = Builder {
251 builder,
252 bbox: RectF::new(),
253 };
254
255 let stack = ArgumentsStack {
256 data: &mut [0.0; MAX_ARGUMENTS_STACK_LEN], // 2052B
257 len: 0,
258 max_len: MAX_ARGUMENTS_STACK_LEN,
259 };
260 let mut parser = CharStringParser {
261 stack,
262 builder: &mut inner_builder,
263 x: 0.0,
264 y: 0.0,
265 has_move_to: false,
266 is_first_move_to: true,
267 width_only: false,
268 };
269 _parse_char_string(&mut ctx, data, 0, &mut parser)?;
270 // let _ = _parse_char_string(&mut ctx, data, 0.0, 0.0, &mut stack, 0, &mut inner_builder)?;
271
272 let bbox = parser.builder.bbox;
273
274 // Check that bbox was changed.
275 if bbox.is_default() {
276 return Err(CFFError::ZeroBBox);
277 }
278
279 bbox.to_rect().ok_or(CFFError::BboxOverflow)
280}
281
282fn _parse_char_string(
283 ctx: &mut CharStringParserContext,
284 char_string: &[u8],
285 depth: u8,
286 p: &mut CharStringParser,
287) -> Result<(), CFFError> {
288 let mut s = Stream::new(char_string);
289 while !s.at_end() {
290 let op = s.read::<u8>().ok_or(CFFError::ReadOutOfBounds)?;
291 match op {
292 0 | 2 | 9 | 11 | 13 | 14 | 17 => {
293 // Reserved.
294 return Err(CFFError::InvalidOperator);
295 }
296 operator::HORIZONTAL_STEM
297 | operator::VERTICAL_STEM
298 | operator::HORIZONTAL_STEM_HINT_MASK
299 | operator::VERTICAL_STEM_HINT_MASK => {
300 // y dy {dya dyb}* hstem
301 // x dx {dxa dxb}* vstem
302 // y dy {dya dyb}* hstemhm
303 // x dx {dxa dxb}* vstemhm
304
305 ctx.stems_len += p.stack.len() as u32 >> 1;
306
307 // We are ignoring the hint operators.
308 p.stack.clear();
309 }
310 operator::VERTICAL_MOVE_TO => {
311 p.parse_vertical_move_to(0)?;
312 }
313 operator::LINE_TO => {
314 p.parse_line_to()?;
315 }
316 operator::HORIZONTAL_LINE_TO => {
317 p.parse_horizontal_line_to()?;
318 }
319 operator::VERTICAL_LINE_TO => {
320 p.parse_vertical_line_to()?;
321 }
322 operator::CURVE_TO => {
323 p.parse_curve_to()?;
324 }
325 operator::CALL_LOCAL_SUBROUTINE => {
326 if p.stack.is_empty() {
327 return Err(CFFError::InvalidArgumentsStackLength);
328 }
329
330 if depth == STACK_LIMIT {
331 return Err(CFFError::NestingLimitReached);
332 }
333
334 let subroutine_bias = calc_subroutine_bias(ctx.metadata.local_subrs.len());
335 let index = conv_subroutine_index(p.stack.pop(), subroutine_bias)?;
336 let char_string = ctx
337 .metadata
338 .local_subrs
339 .get(index)
340 .ok_or(CFFError::InvalidSubroutineIndex)?;
341 _parse_char_string(ctx, char_string, depth + 1, p)?;
342 }
343 TWO_BYTE_OPERATOR_MARK => {
344 // flex
345 let op2 = s.read::<u8>().ok_or(CFFError::ReadOutOfBounds)?;
346 match op2 {
347 operator::HFLEX => p.parse_hflex()?,
348 operator::FLEX => p.parse_flex()?,
349 operator::HFLEX1 => p.parse_hflex1()?,
350 operator::FLEX1 => p.parse_flex1()?,
351 _ => return Err(CFFError::UnsupportedOperator),
352 }
353 }
354 operator::VS_INDEX => {
355 // |- ivs vsindex (15) |-
356
357 // `vsindex` must precede the first `blend` operator, and may occur only once.
358 if ctx.had_blend || ctx.had_vsindex {
359 // TODO: maybe add a custom error
360 return Err(CFFError::InvalidOperator);
361 }
362
363 if p.stack.len() != 1 {
364 return Err(CFFError::InvalidArgumentsStackLength);
365 }
366
367 let index = u16::try_num_from(p.stack.pop())
368 .ok_or(CFFError::InvalidItemVariationDataIndex)?;
369 ctx.update_scalars(index)?;
370
371 ctx.had_vsindex = true;
372
373 p.stack.clear();
374 }
375 operator::BLEND => {
376 // num(0)..num(n-1), delta(0,0)..delta(k-1,0),
377 // delta(0,1)..delta(k-1,1) .. delta(0,n-1)..delta(k-1,n-1)
378 // n blend (16) val(0)..val(n-1)
379
380 ctx.had_blend = true;
381
382 let n = u16::try_num_from(p.stack.pop())
383 .ok_or(CFFError::InvalidNumberOfBlendOperands)?;
384 let k = ctx.scalars.len();
385
386 let len = usize::from(n) * (usize::from(k) + 1);
387 if p.stack.len() < len {
388 return Err(CFFError::InvalidArgumentsStackLength);
389 }
390
391 let start = p.stack.len() - len;
392 for i in (0..n).rev() {
393 for j in 0..k {
394 let delta = p.stack.pop();
395 p.stack.data[start + usize::from(i)] += delta * ctx.scalars.at(k - j - 1);
396 }
397 }
398 }
399 operator::HINT_MASK | operator::COUNTER_MASK => {
400 ctx.stems_len += p.stack.len() as u32 >> 1;
401 s.advance(usize::num_from((ctx.stems_len + 7) >> 3));
402
403 // We are ignoring the hint operators.
404 p.stack.clear();
405 }
406 operator::MOVE_TO => {
407 p.parse_move_to(0)?;
408 }
409 operator::HORIZONTAL_MOVE_TO => {
410 p.parse_horizontal_move_to(0)?;
411 }
412 operator::CURVE_LINE => {
413 p.parse_curve_line()?;
414 }
415 operator::LINE_CURVE => {
416 p.parse_line_curve()?;
417 }
418 operator::VV_CURVE_TO => {
419 p.parse_vv_curve_to()?;
420 }
421 operator::HH_CURVE_TO => {
422 p.parse_hh_curve_to()?;
423 }
424 operator::SHORT_INT => {
425 let n = s.read::<i16>().ok_or(CFFError::ReadOutOfBounds)?;
426 p.stack.push(f32::from(n))?;
427 }
428 operator::CALL_GLOBAL_SUBROUTINE => {
429 if p.stack.is_empty() {
430 return Err(CFFError::InvalidArgumentsStackLength);
431 }
432
433 if depth == STACK_LIMIT {
434 return Err(CFFError::NestingLimitReached);
435 }
436
437 let subroutine_bias = calc_subroutine_bias(ctx.metadata.global_subrs.len());
438 let index = conv_subroutine_index(p.stack.pop(), subroutine_bias)?;
439 let char_string = ctx
440 .metadata
441 .global_subrs
442 .get(index)
443 .ok_or(CFFError::InvalidSubroutineIndex)?;
444 _parse_char_string(ctx, char_string, depth + 1, p)?;
445 }
446 operator::VH_CURVE_TO => {
447 p.parse_vh_curve_to()?;
448 }
449 operator::HV_CURVE_TO => {
450 p.parse_hv_curve_to()?;
451 }
452 32..=246 => {
453 p.parse_int1(op)?;
454 }
455 247..=250 => {
456 p.parse_int2(op, &mut s)?;
457 }
458 251..=254 => {
459 p.parse_int3(op, &mut s)?;
460 }
461 operator::FIXED_16_16 => {
462 p.parse_fixed(&mut s)?;
463 }
464 }
465 }
466
467 Ok(())
468}
469
470/// A [Compact Font Format 2 Table](
471/// https://docs.microsoft.com/en-us/typography/opentype/spec/cff2).
472#[derive(Clone, Copy, Default)]
473pub struct Table<'a> {
474 global_subrs: Index<'a>,
475 local_subrs: Index<'a>,
476 char_strings: Index<'a>,
477 item_variation_store: ItemVariationStore<'a>,
478}
479
480impl<'a> Table<'a> {
481 /// Parses a table from raw data.
482 pub fn parse(data: &'a [u8]) -> Option<Self> {
483 let mut s = Stream::new(data);
484
485 // Parse Header.
486 let major = s.read::<u8>()?;
487 s.skip::<u8>(); // minor
488 let header_size = s.read::<u8>()?;
489 let top_dict_length = s.read::<u16>()?;
490
491 if major != 2 {
492 return None;
493 }
494
495 // Jump to Top DICT. It's not necessarily right after the header.
496 if header_size > 5 {
497 s.advance(usize::from(header_size) - 5);
498 }
499
500 let top_dict_data = s.read_bytes(usize::from(top_dict_length))?;
501 let top_dict = parse_top_dict(top_dict_data)?;
502
503 let mut metadata = Self::default();
504
505 // Parse Global Subroutines INDEX.
506 metadata.global_subrs = parse_index::<u32>(&mut s)?;
507
508 metadata.char_strings = {
509 let mut s = Stream::new_at(data, top_dict.char_strings_offset)?;
510 parse_index::<u32>(&mut s)?
511 };
512
513 if let Some(offset) = top_dict.variation_store_offset {
514 let mut s = Stream::new_at(data, offset)?;
515 s.skip::<u16>(); // length
516 metadata.item_variation_store = ItemVariationStore::parse(s)?;
517 }
518
519 // TODO: simplify
520 if let Some(offset) = top_dict.font_dict_index_offset {
521 let mut s = Stream::new_at(data, offset)?;
522 'outer: for font_dict_data in parse_index::<u32>(&mut s)? {
523 if let Some(private_dict_range) = parse_font_dict(font_dict_data) {
524 // 'Private DICT size and offset, from start of the CFF2 table.'
525 let private_dict_data = data.get(private_dict_range.clone())?;
526 if let Some(subroutines_offset) = parse_private_dict(private_dict_data) {
527 // 'The local subroutines offset is relative to the beginning
528 // of the Private DICT data.'
529 if let Some(start) =
530 private_dict_range.start.checked_add(subroutines_offset)
531 {
532 let data = data.get(start..data.len())?;
533 let mut s = Stream::new(data);
534 metadata.local_subrs = parse_index::<u32>(&mut s)?;
535 break 'outer;
536 }
537 }
538 }
539 }
540 }
541
542 Some(metadata)
543 }
544
545 /// Outlines a glyph.
546 pub fn outline(
547 &self,
548 coordinates: &[NormalizedCoordinate],
549 glyph_id: GlyphId,
550 builder: &mut dyn OutlineBuilder,
551 ) -> Result<Rect, CFFError> {
552 let data = self
553 .char_strings
554 .get(u32::from(glyph_id.0))
555 .ok_or(CFFError::NoGlyph)?;
556 parse_char_string(data, self, coordinates, builder)
557 }
558}
559
560impl core::fmt::Debug for Table<'_> {
561 fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
562 write!(f, "Table {{ ... }}")
563 }
564}
565