-
Notifications
You must be signed in to change notification settings - Fork 17
/
algorithm.py
673 lines (520 loc) · 21 KB
/
algorithm.py
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
# This file is part of python-bidi
#
# python-bidi is free software: you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
# Copyright (C) 2008-2010 Yaacov Zamir <kzamir_a_walla.co.il>,
# Copyright (C) 2010-2015 Meir kriheli <[email protected]>.
"bidirectional algorithm implementation"
import inspect
import sys
from collections import deque
from typing import Optional, Union
from unicodedata import bidirectional, mirrored
from .mirror import MIRRORED
StrOrBytes = Union[str, bytes]
# Some definitions
PARAGRAPH_LEVELS = {"L": 0, "AL": 1, "R": 1}
EXPLICIT_LEVEL_LIMIT = 62
def _LEAST_GREATER_ODD(x):
return (x + 1) | 1
def _LEAST_GREATER_EVEN(x):
return (x + 2) & ~1
X2_X5_MAPPINGS = {
"RLE": (_LEAST_GREATER_ODD, "N"),
"LRE": (_LEAST_GREATER_EVEN, "N"),
"RLO": (_LEAST_GREATER_ODD, "R"),
"LRO": (_LEAST_GREATER_EVEN, "L"),
}
# Added 'B' so X6 won't execute in that case and X8 will run it's course
X6_IGNORED = list(X2_X5_MAPPINGS.keys()) + ["BN", "PDF", "B"]
X9_REMOVED = list(X2_X5_MAPPINGS.keys()) + ["BN", "PDF"]
def _embedding_direction(x):
return ("L", "R")[x % 2]
_IS_UCS2 = sys.maxunicode == 65535
_SURROGATE_MIN, _SURROGATE_MAX = 55296, 56319 # D800, DBFF
def debug_storage(storage, base_info=False, chars=True, runs=False):
"Display debug information for the storage"
stderr = sys.stderr
caller = inspect.stack()[1][3]
stderr.write(f"in {caller}\n")
if base_info:
stderr.write(" base level : %d\n" % storage["base_level"])
stderr.write(" base dir : {}\n".format(storage["base_dir"]))
if runs:
stderr.write(" runs : {}\n".format(list(storage["runs"])))
if chars:
output = " Chars : "
for _ch in storage["chars"]:
if _ch != "\n":
output += _ch["ch"]
else:
output += "C"
stderr.write(output + "\n")
output = " Res. levels : {}\n".format("".join(
[str(_ch["level"]) for _ch in storage["chars"]]
))
stderr.write(output)
_types = [_ch["type"].ljust(3) for _ch in storage["chars"]]
for i in range(3):
output = " %s\n" if i else " Res. types : %s\n"
stderr.write(output % "".join([_t[i] for _t in _types]))
def get_base_level(text, upper_is_rtl=False) -> int:
"""Get the paragraph base embedding level. Returns 0 for LTR,
1 for RTL.
`text` a unicode object.
Set `upper_is_rtl` to True to treat upper case chars as strong 'R'
for debugging (default: False).
"""
base_level = None
prev_surrogate = False
# P2
for _ch in text:
# surrogate in case of ucs2
if _IS_UCS2 and (_SURROGATE_MIN <= ord(_ch) <= _SURROGATE_MAX):
prev_surrogate = _ch
continue
elif prev_surrogate:
_ch = prev_surrogate + _ch
prev_surrogate = False
# treat upper as RTL ?
if upper_is_rtl and _ch.isupper():
base_level = 1
break
bidi_type = bidirectional(_ch)
if bidi_type in ("AL", "R"):
base_level = 1
break
elif bidi_type == "L":
base_level = 0
break
# P3
if base_level is None:
base_level = 0
return base_level
def get_embedding_levels(text, storage, upper_is_rtl=False, debug=False):
"""Get the paragraph base embedding level and direction,
set the storage to the array of chars"""
prev_surrogate = False
base_level = storage["base_level"]
# preset the storage's chars
for _ch in text:
if _IS_UCS2 and (_SURROGATE_MIN <= ord(_ch) <= _SURROGATE_MAX):
prev_surrogate = _ch
continue
elif prev_surrogate:
_ch = prev_surrogate + _ch
prev_surrogate = False
bidi_type = "R" if upper_is_rtl and _ch.isupper() else bidirectional(_ch)
storage["chars"].append(
{"ch": _ch, "level": base_level, "type": bidi_type, "orig": bidi_type}
)
if debug:
debug_storage(storage, base_info=True)
def explicit_embed_and_overrides(storage, debug=False):
"""Apply X1 to X9 rules of the unicode algorithm.
See http://unicode.org/reports/tr9/#Explicit_Levels_and_Directions
"""
overflow_counter = almost_overflow_counter = 0
directional_override = "N"
levels = deque()
# X1
embedding_level = storage["base_level"]
for _ch in storage["chars"]:
bidi_type = _ch["type"]
level_func, override = X2_X5_MAPPINGS.get(bidi_type, (None, None))
if level_func:
# So this is X2 to X5
# if we've past EXPLICIT_LEVEL_LIMIT, note it and do nothing
if overflow_counter != 0:
overflow_counter += 1
continue
new_level = level_func(embedding_level)
if new_level < EXPLICIT_LEVEL_LIMIT:
levels.append((embedding_level, directional_override))
embedding_level, directional_override = new_level, override
elif embedding_level == EXPLICIT_LEVEL_LIMIT - 2:
# The new level is invalid, but a valid level can still be
# achieved if this level is 60 and we encounter an RLE or
# RLO further on. So record that we 'almost' overflowed.
almost_overflow_counter += 1
else:
overflow_counter += 1
else:
# X6
if bidi_type not in X6_IGNORED:
_ch["level"] = embedding_level
if directional_override != "N":
_ch["type"] = directional_override
# X7
elif bidi_type == "PDF":
if overflow_counter:
overflow_counter -= 1
elif (
almost_overflow_counter
and embedding_level != EXPLICIT_LEVEL_LIMIT - 1
):
almost_overflow_counter -= 1
elif levels:
embedding_level, directional_override = levels.pop()
# X8
elif bidi_type == "B":
levels.clear()
overflow_counter = almost_overflow_counter = 0
embedding_level = _ch["level"] = storage["base_level"]
directional_override = "N"
# Removes the explicit embeds and overrides of types
# RLE, LRE, RLO, LRO, PDF, and BN. Adjusts extended chars
# next and prev as well
# Applies X9. See http://unicode.org/reports/tr9/#X9
storage["chars"] = [
_ch for _ch in storage["chars"] if _ch["type"] not in X9_REMOVED
]
calc_level_runs(storage)
if debug:
debug_storage(storage, runs=True)
def calc_level_runs(storage):
"""Split the storage to run of char types at the same level.
Applies X10. See http://unicode.org/reports/tr9/#X10
"""
# run level depends on the higher of the two levels on either side of
# the boundary If the higher level is odd, the type is R; otherwise,
# it is L
storage["runs"].clear()
chars = storage["chars"]
# empty string ?
if not chars:
return
def calc_level_run(b_l, b_r):
return ["L", "R"][max(b_l, b_r) % 2]
first_char = chars[0]
sor = calc_level_run(storage["base_level"], first_char["level"])
eor = None
run_start = run_length = 0
curr_level, curr_type = 0, ""
prev_level, prev_type = first_char["level"], first_char["type"]
for _ch in chars:
curr_level, curr_type = _ch["level"], _ch["type"]
if curr_level == prev_level:
run_length += 1
else:
eor = calc_level_run(prev_level, curr_level)
storage["runs"].append(
{
"sor": sor,
"eor": eor,
"start": run_start,
"type": prev_type,
"length": run_length,
}
)
sor = eor
run_start += run_length
run_length = 1
prev_level, prev_type = curr_level, curr_type
# for the last char/runlevel
eor = calc_level_run(curr_level, storage["base_level"])
storage["runs"].append(
{
"sor": sor,
"eor": eor,
"start": run_start,
"type": curr_type,
"length": run_length,
}
)
def resolve_weak_types(storage, debug=False):
"""Resolve weak type rules W1 - W3.
See: http://unicode.org/reports/tr9/#Resolving_Weak_Types
"""
for run in storage["runs"]:
prev_strong = prev_type = run["sor"]
start, length = run["start"], run["length"]
chars = storage["chars"][start : start + length]
for _ch in chars:
# W1. Examine each nonspacing mark (NSM) in the level run, and
# change the type of the NSM to the type of the previous character.
# If the NSM is at the start of the level run, it will get the type
# of sor.
bidi_type = _ch["type"]
if bidi_type == "NSM":
_ch["type"] = bidi_type = prev_type
# W2. Search backward from each instance of a European number until
# the first strong type (R, L, AL, or sor) is found. If an AL is
# found, change the type of the European number to Arabic number.
if bidi_type == "EN" and prev_strong == "AL":
_ch["type"] = "AN"
# update prev_strong if needed
if bidi_type in ("R", "L", "AL"):
prev_strong = bidi_type
prev_type = _ch["type"]
# W3. Change all ALs to R
for _ch in chars:
if _ch["type"] == "AL":
_ch["type"] = "R"
# W4. A single European separator between two European numbers changes
# to a European number. A single common separator between two numbers of
# the same type changes to that type.
for idx in range(1, len(chars) - 1):
bidi_type = chars[idx]["type"]
prev_type = chars[idx - 1]["type"]
next_type = chars[idx + 1]["type"]
if bidi_type == "ES" and (prev_type == next_type == "EN"):
chars[idx]["type"] = "EN"
if (
bidi_type == "CS"
and prev_type == next_type
and prev_type in ("AN", "EN")
):
chars[idx]["type"] = prev_type
# W5. A sequence of European terminators adjacent to European numbers
# changes to all European numbers.
for idx in range(len(chars)):
if chars[idx]["type"] == "EN":
for et_idx in range(idx - 1, -1, -1):
if chars[et_idx]["type"] == "ET":
chars[et_idx]["type"] = "EN"
else:
break
for et_idx in range(idx + 1, len(chars)):
if chars[et_idx]["type"] == "ET":
chars[et_idx]["type"] = "EN"
else:
break
# W6. Otherwise, separators and terminators change to Other Neutral.
for _ch in chars:
if _ch["type"] in ("ET", "ES", "CS"):
_ch["type"] = "ON"
# W7. Search backward from each instance of a European number until the
# first strong type (R, L, or sor) is found. If an L is found, then
# change the type of the European number to L.
prev_strong = run["sor"]
for _ch in chars:
if _ch["type"] == "EN" and prev_strong == "L":
_ch["type"] = "L"
if _ch["type"] in ("L", "R"):
prev_strong = _ch["type"]
if debug:
debug_storage(storage, runs=True)
def resolve_neutral_types(storage, debug):
"""Resolving neutral types. Implements N1 and N2
See: http://unicode.org/reports/tr9/#Resolving_Neutral_Types
"""
prev_bidi_type = ""
for run in storage["runs"]:
start, length = run["start"], run["length"]
# use sor and eor
chars = (
[{"type": run["sor"]}]
+ storage["chars"][start : start + length]
+ [{"type": run["eor"]}]
)
total_chars = len(chars)
seq_start = None
for idx in range(total_chars):
_ch = chars[idx]
if _ch["type"] in ("B", "S", "WS", "ON"):
# N1. A sequence of neutrals takes the direction of the
# surrounding strong text if the text on both sides has the same
# direction. European and Arabic numbers act as if they were R
# in terms of their influence on neutrals. Start-of-level-run
# (sor) and end-of-level-run (eor) are used at level run
# boundaries.
if seq_start is None:
seq_start = idx
prev_bidi_type = chars[idx - 1]["type"]
else:
if seq_start is not None:
next_bidi_type = chars[idx]["type"]
if prev_bidi_type in ("AN", "EN"):
prev_bidi_type = "R"
if next_bidi_type in ("AN", "EN"):
next_bidi_type = "R"
for seq_idx in range(seq_start, idx):
if prev_bidi_type == next_bidi_type:
chars[seq_idx]["type"] = prev_bidi_type
else:
# N2. Any remaining neutrals take the embedding
# direction. The embedding direction for the given
# neutral character is derived from its embedding
# level: L if the character is set to an even level,
# and R if the level is odd.
chars[seq_idx]["type"] = _embedding_direction(
chars[seq_idx]["level"]
)
seq_start = None
if debug:
debug_storage(storage)
def resolve_implicit_levels(storage, debug):
"""Resolving implicit levels (I1, I2)
See: http://unicode.org/reports/tr9/#Resolving_Implicit_Levels
"""
for run in storage["runs"]:
start, length = run["start"], run["length"]
chars = storage["chars"][start : start + length]
for _ch in chars:
# only those types are allowed at this stage
assert _ch["type"] in ("L", "R", "EN", "AN"), (
"{} not allowed here".format(_ch["type"])
)
if _embedding_direction(_ch["level"]) == "L":
# I1. For all characters with an even (left-to-right) embedding
# direction, those of type R go up one level and those of type
# AN or EN go up two levels.
if _ch["type"] == "R":
_ch["level"] += 1
elif _ch["type"] != "L":
_ch["level"] += 2
else:
# I2. For all characters with an odd (right-to-left) embedding
# direction, those of type L, EN or AN go up one level.
if _ch["type"] != "R":
_ch["level"] += 1
if debug:
debug_storage(storage, runs=True)
def reverse_contiguous_sequence(
chars, line_start, line_end, highest_level, lowest_odd_level
):
"""L2. From the highest level found in the text to the lowest odd
level on each line, including intermediate levels not actually
present in the text, reverse any contiguous sequence of characters
that are at that level or higher.
"""
for level in range(highest_level, lowest_odd_level - 1, -1):
_start = _end = None
for run_idx in range(line_start, line_end + 1):
run_ch = chars[run_idx]
if run_ch["level"] >= level:
if _start is None:
_start = _end = run_idx
else:
_end = run_idx
else:
if _end is not None:
chars[_start : +_end + 1] = reversed(chars[_start : +_end + 1])
_start = _end = None
# anything remaining ?
if _start is not None and _end is not None:
chars[_start : +_end + 1] = reversed(chars[_start : +_end + 1])
def reorder_resolved_levels(storage, debug):
"""L1 and L2 rules"""
# Applies L1.
should_reset = True
chars = storage["chars"]
for _ch in chars[::-1]:
# L1. On each line, reset the embedding level of the following
# characters to the paragraph embedding level:
if _ch["orig"] in ("B", "S"):
# 1. Segment separators,
# 2. Paragraph separators,
_ch["level"] = storage["base_level"]
should_reset = True
elif should_reset and _ch["orig"] in ("BN", "WS"):
# 3. Any sequence of whitespace characters preceding a segment
# separator or paragraph separator
# 4. Any sequence of white space characters at the end of the
# line.
_ch["level"] = storage["base_level"]
else:
should_reset = False
max_len = len(chars)
# L2 should be per line
# Calculates highest level and lowest odd level on the fly.
line_start = line_end = 0
highest_level = 0
lowest_odd_level = EXPLICIT_LEVEL_LIMIT
for idx in range(max_len):
_ch = chars[idx]
# calc the levels
char_level = _ch["level"]
if char_level > highest_level:
highest_level = char_level
if char_level % 2 and char_level < lowest_odd_level:
lowest_odd_level = char_level
if _ch["orig"] == "B" or idx == max_len - 1:
line_end = idx
# omit line breaks
if _ch["orig"] == "B":
line_end -= 1
reverse_contiguous_sequence(
chars, line_start, line_end, highest_level, lowest_odd_level
)
# reset for next line run
line_start = idx + 1
highest_level = 0
lowest_odd_level = EXPLICIT_LEVEL_LIMIT
if debug:
debug_storage(storage)
def apply_mirroring(storage, debug):
"""Applies L4: mirroring
See: http://unicode.org/reports/tr9/#L4
"""
# L4. A character is depicted by a mirrored glyph if and only if (a) the
# resolved directionality of that character is R, and (b) the
# Bidi_Mirrored property value of that character is true.
for _ch in storage["chars"]:
unichar = _ch["ch"]
if mirrored(unichar) and _embedding_direction(_ch["level"]) == "R":
_ch["ch"] = MIRRORED.get(unichar, unichar)
if debug:
debug_storage(storage)
def get_empty_storage():
"""Return an empty storage skeleton, usable for testing"""
return {
"base_level": None,
"base_dir": None,
"chars": [],
"runs": deque(),
}
def get_display(
str_or_bytes: StrOrBytes,
encoding: str = "utf-8",
upper_is_rtl: bool = False,
base_dir: Optional[str] = None,
debug: bool = False,
) -> StrOrBytes:
"""Accepts `str` or `bytes`. In case it's `bytes`, `encoding`
is needed as the algorithm works on `str` (default:"utf-8").
Set `upper_is_rtl` to True to treat upper case chars as strong 'R'
for debugging (default: False).
Set `base_dir` to 'L' or 'R' to override the calculated base_level.
Set `debug` to True to display (using sys.stderr) the steps taken with the
algorithm.
Returns the display layout, either as unicode or `encoding` encoded
string.
"""
storage = get_empty_storage()
# utf-8 ? we need unicode
if isinstance(str_or_bytes, bytes):
text = str_or_bytes.decode(encoding)
was_decoded = True
else:
text = str_or_bytes
was_decoded = False
if base_dir is None:
base_level = get_base_level(text, upper_is_rtl)
else:
base_level = PARAGRAPH_LEVELS[base_dir]
storage["base_level"] = base_level
storage["base_dir"] = ("L", "R")[base_level]
get_embedding_levels(text, storage, upper_is_rtl, debug)
explicit_embed_and_overrides(storage, debug)
resolve_weak_types(storage, debug)
resolve_neutral_types(storage, debug)
resolve_implicit_levels(storage, debug)
reorder_resolved_levels(storage, debug)
apply_mirroring(storage, debug)
chars = storage["chars"]
display = "".join([_ch["ch"] for _ch in chars])
if was_decoded:
display = display.encode(encoding)
return display