-
-
Notifications
You must be signed in to change notification settings - Fork 1.6k
/
regex.cr
578 lines (541 loc) · 19.6 KB
/
regex.cr
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
require "./regex/*"
# A `Regex` represents a regular expression, a pattern that describes the
# contents of strings. A `Regex` can determine whether or not a string matches
# its description, and extract the parts of the string that match.
#
# A `Regex` can be created using the literal syntax, in which it is delimited by
# forward slashes (`/`):
#
# ```
# /hay/ =~ "haystack" # => 0
# /y/.match("haystack") # => #<Regex::MatchData "y">
# ```
#
# Interpolation works in regular expression literals just as it does in string
# literals. Be aware that using this feature will cause an exception to be
# raised at runtime, if the resulting string would not be a valid regular
# expression.
#
# ```
# x = "a"
# /#{x}/.match("asdf") # => #<Regex::MatchData "a">
# x = "("
# /#{x}/ # raises ArgumentError
# ```
#
# When we check to see if a particular regular expression describes a string,
# we can say that we are performing a match or matching one against the other.
# If we find that a regular expression does describe a string, we say that it
# matches, and we can refer to a part of the string that was described as
# a match.
#
# Here `"haystack"` does not contain the pattern `/needle/`, so it doesn't match:
#
# ```
# /needle/.match("haystack") # => nil
# ```
#
# Here `"haystack"` contains the pattern `/hay/`, so it matches:
#
# ```
# /hay/.match("haystack") # => #<Regex::MatchData "hay">
# ```
#
# Regex methods that perform a match usually return a truthy value if there was
# a match and `nil` if there was no match. After performing a match, the
# special variable `$~` will be an instance of `Regex::MatchData` if it matched, `nil`
# otherwise.
#
# When matching a regular expression using `=~` (either `String#=~` or
# `Regex#=~`), the returned value will be the index of the first match in the
# string if the expression matched, `nil` otherwise.
#
# ```
# /stack/ =~ "haystack" # => 3
# "haystack" =~ /stack/ # => 3
# $~ # => #<Regex::MatchData "stack">
# /needle/ =~ "haystack" # => nil
# "haystack" =~ /needle/ # => nil
# $~ # raises Exception
# ```
#
# When matching a regular expression using `#match` (either `String#match` or
# `Regex#match`), the returned value will be a `Regex::MatchData` if the expression
# matched, `nil` otherwise.
#
# ```
# /hay/.match("haystack") # => #<Regex::MatchData "hay">
# "haystack".match(/hay/) # => #<Regex::MatchData "hay">
# $~ # => #<Regex::MatchData "hay">
# /needle/.match("haystack") # => nil
# "haystack".match(/needle/) # => nil
# $~ # raises Exception
# ```
#
# [Regular expressions](https://en.wikipedia.org/wiki/Regular_expression)
# have their own language for describing strings.
#
# Many programming languages and tools implement their own regular expression
# language, but Crystal uses [PCRE](http://www.pcre.org/), a popular C library
# for providing regular expressions. Here give a brief summary of the most
# basic features of regular expressions - grouping, repetition, and
# alternation - but the feature set of PCRE extends far beyond these, and we
# don't attempt to describe it in full here. For more information, refer to
# the PCRE documentation, especially the
# [full pattern syntax](http://www.pcre.org/original/doc/html/pcrepattern.html)
# or
# [syntax quick reference](http://www.pcre.org/original/doc/html/pcresyntax.html).
#
# The regular expression language can be used to match much more than just the
# static substrings in the above examples. Certain characters, called
# [metacharacters](http://www.pcre.org/original/doc/html/pcrepattern.html#SEC4),
# are given special treatment in regular expressions, and can be used to
# describe more complex patterns. To match metacharacters literally in a
# regular expression, they must be escaped by being preceded with a backslash
# (`\`). `escape` will do this automatically for a given String.
#
# A group of characters (often called a capture group or
# [subpattern](http://www.pcre.org/original/doc/html/pcrepattern.html#SEC14))
# can be identified by enclosing it in parentheses (`()`). The contents of
# each capture group can be extracted on a successful match:
#
# ```
# /a(sd)f/.match("_asdf_") # => #<Regex::MatchData "asdf" 1:"sd">
# /a(sd)f/.match("_asdf_").try &.[1] # => "sd"
# /a(?<grp>sd)f/.match("_asdf_") # => #<Regex::MatchData "asdf" grp:"sd">
# /a(?<grp>sd)f/.match("_asdf_").try &.["grp"] # => "sd"
# ```
#
# Capture groups are indexed starting from 1. Methods that accept a capture
# group index will usually also accept 0 to refer to the full match. Capture
# groups can also be given names, using the `(?<name>...)` syntax, as in the
# previous example.
#
# Following a match, the special variables $N (e.g., $1, $2, $3, ...) can be used
# to access a capture group. Trying to access an invalid capture group will raise an
# exception. Note that it is possible to have a successful match with a nil capture:
#
# ```
# /(spice)(s)?/.match("spice") # => #<Regex::MatchData "spice" 1:"spice" 2:nil>
# $1 # => "spice"
# $2 # => raises Exception
# ```
#
# This can be mitigated by using the nilable version of the above: $N?,
# (e.g., $1? $2?, $3?, ...). Changing the above to use `$2?` instead of `$2`
# would return `nil`. `$2?.nil?` would return `true`.
#
# A character or group can be
# [repeated](http://www.pcre.org/original/doc/html/pcrepattern.html#SEC17)
# or made optional using an asterisk (`*` - zero or more), a plus sign
# (`+` - one or more), integer bounds in curly braces
# (`{n,m}`) (at least `n`, no more than `m`), or a question mark
# (`?`) (zero or one).
#
# ```
# /fo*/.match("_f_") # => #<Regex::MatchData "f">
# /fo+/.match("_f_") # => nil
# /fo*/.match("_foo_") # => #<Regex::MatchData "foo">
# /fo{3,}/.match("_foo_") # => nil
# /fo{1,3}/.match("_foo_") # => #<Regex::MatchData "foo">
# /fo*/.match("_foo_") # => #<Regex::MatchData "foo">
# /fo*/.match("_foooooooo_") # => #<Regex::MatchData "foooooooo">
# /fo{,3}/.match("_foooo_") # => nil
# /f(op)*/.match("fopopo") # => #<Regex::MatchData "fopop" 1: "op">
# /foo?bar/.match("foobar") # => #<Regex::MatchData "foobar">
# /foo?bar/.match("fobar") # => #<Regex::MatchData "fobar">
# ```
#
# Alternatives can be separated using a
# [vertical bar](http://www.pcre.org/original/doc/html/pcrepattern.html#SEC12)
# (`|`). Any single character can be represented by
# [dot](http://www.pcre.org/original/doc/html/pcrepattern.html#SEC7)
# (`.`). When matching only one character, specific
# alternatives can be expressed as a
# [character class](http://www.pcre.org/original/doc/html/pcrepattern.html#SEC9),
# enclosed in square brackets (`[]`):
#
# ```
# /foo|bar/.match("foo") # => #<Regex::MatchData "foo">
# /foo|bar/.match("bar") # => #<Regex::MatchData "bar">
# /_(x|y)_/.match("_x_") # => #<Regex::MatchData "_x_" 1: "x">
# /_(x|y)_/.match("_y_") # => #<Regex::MatchData "_y_" 1: "y">
# /_(x|y)_/.match("_(x|y)_") # => nil
# /_(x|y)_/.match("_(x|y)_") # => nil
# /_._/.match("_x_") # => #<Regex::MatchData "_x_">
# /_[xyz]_/.match("_x_") # => #<Regex::MatchData "_x_">
# /_[a-z]_/.match("_x_") # => #<Regex::MatchData "_x_">
# /_[^a-z]_/.match("_x_") # => nil
# /_[^a-wy-z]_/.match("_x_") # => #<Regex::MatchData "_x_">
# ```
#
# Regular expressions can be defined with these 3
# [optional flags](http://www.pcre.org/original/doc/html/pcreapi.html#SEC11):
#
# * `i`: ignore case (PCRE_CASELESS)
# * `m`: multiline (PCRE_MULTILINE and PCRE_DOTALL)
# * `x`: extended (PCRE_EXTENDED)
#
# ```
# /asdf/ =~ "ASDF" # => nil
# /asdf/i =~ "ASDF" # => 0
# /^z/i =~ "ASDF\nZ" # => nil
# /^z/im =~ "ASDF\nZ" # => 5
# ```
#
# PCRE supports other encodings, but Crystal strings are UTF-8 only, so Crystal
# regular expressions are also UTF-8 only (by default).
#
# PCRE optionally permits named capture groups (named subpatterns) to not be
# unique. Crystal exposes the name table of a `Regex` as a
# `Hash` of `String` => `Int32`, and therefore requires named capture groups to have
# unique names within a single `Regex`.
class Regex
# List of metacharacters that need to be escaped.
#
# See `Regex.needs_escape?` and `Regex.escape`.
SPECIAL_CHARACTERS = {
' ', '.', '\\', '+', '*', '?', '[',
'^', ']', '$', '(', ')', '{', '}',
'=', '!', '<', '>', '|', ':', '-',
}
@[Flags]
enum Options
# Case insensitive match.
IGNORE_CASE = 1
# PCRE native `PCRE_MULTILINE` flag is `2`, and `PCRE_DOTALL` is `4`
# - `PCRE_DOTALL` changes the "`.`" meaning
# - `PCRE_MULTILINE` changes "`^`" and "`$`" meanings
#
# Crystal modifies this meaning to have essentially one unique "`m`"
# flag that activates both behaviours, so here we do the same by
# mapping `MULTILINE` to `PCRE_MULTILINE | PCRE_DOTALL`.
MULTILINE = 6
# Ignore white space and `#` comments.
EXTENDED = 8
# Force pattern anchoring.
ANCHORED = 16
# :nodoc:
UTF_8 = 0x00000800
# :nodoc:
NO_UTF8_CHECK = 0x00002000
# :nodoc:
DUPNAMES = 0x00080000
end
# Returns a `Regex::Options` representing the optional flags applied to this `Regex`.
#
# ```
# /ab+c/ix.options # => Regex::Options::IGNORE_CASE | Regex::Options::EXTENDED
# /ab+c/ix.options.to_s # => "IGNORE_CASE | EXTENDED"
# ```
getter options : Options
# Returns the original `String` representation of the `Regex` pattern.
#
# ```
# /ab+c/x.source # => "ab+c"
# ```
getter source : String
# Creates a new `Regex` out of the given source `String`.
#
# ```
# Regex.new("^a-z+:\\s+\\w+") # => /^a-z+:\s+\w+/
# Regex.new("cat", Regex::Options::IGNORE_CASE) # => /cat/i
# options = Regex::Options::IGNORE_CASE | Regex::Options::EXTENDED
# Regex.new("dog", options) # => /dog/ix
# ```
def initialize(source : String, @options : Options = Options::None)
# PCRE's pattern must have their null characters escaped
source = source.gsub('\u{0}', "\\0")
@source = source
@re = LibPCRE.compile(@source, (options | Options::UTF_8 | Options::NO_UTF8_CHECK | Options::DUPNAMES), out errptr, out erroffset, nil)
raise ArgumentError.new("#{String.new(errptr)} at #{erroffset}") if @re.null?
@extra = LibPCRE.study(@re, 0, out studyerrptr)
raise ArgumentError.new("#{String.new(studyerrptr)}") if @extra.null? && studyerrptr
LibPCRE.full_info(@re, nil, LibPCRE::INFO_CAPTURECOUNT, out @captures)
end
# Determines Regex's source validity. If it is, `nil` is returned.
# If it's not, a `String` containing the error message is returned.
#
# ```
# Regex.error?("(foo|bar)") # => nil
# Regex.error?("(foo|bar") # => "missing ) at 8"
# ```
def self.error?(source)
re = LibPCRE.compile(source, (Options::UTF_8 | Options::NO_UTF8_CHECK | Options::DUPNAMES), out errptr, out erroffset, nil)
if re
nil
else
"#{String.new(errptr)} at #{erroffset}"
end
end
# Returns `true` if *char* need to be escaped, `false` otherwise.
#
# ```
# Regex.needs_escape?('*') # => true
# Regex.needs_escape?('@') # => false
# ```
def self.needs_escape?(char : Char) : Bool
SPECIAL_CHARACTERS.includes?(char)
end
# Returns `true` if *str* need to be escaped, `false` otherwise.
#
# ```
# Regex.needs_escape?("10$") # => true
# Regex.needs_escape?("foo") # => false
# ```
def self.needs_escape?(str : String) : Bool
str.each_char { |char| return true if SPECIAL_CHARACTERS.includes?(char) }
false
end
# Returns a `String` constructed by escaping any metacharacters in *str*.
#
# ```
# string = Regex.escape("\*?{}.") # => "\\*\\?\\{\\}\\."
# /#{string}/ # => /\*\?\{\}\./
# ```
def self.escape(str) : String
String.build do |result|
str.each_byte do |byte|
{% begin %}
case byte.unsafe_chr
when {{*SPECIAL_CHARACTERS}}
result << '\\'
result.write_byte byte
else
result.write_byte byte
end
{% end %}
end
end
end
# Union. Returns a `Regex` that matches any of *patterns*.
#
# All capture groups in the patterns after the first one will have their
# indexes offset.
#
# ```
# re = Regex.union([/skiing/i, "sledding"])
# re.match("Skiing") # => #<Regex::MatchData "Skiing">
# re.match("sledding") # => #<Regex::MatchData "sledding">
# re = Regex.union({/skiing/i, "sledding"})
# re.match("Skiing") # => #<Regex::MatchData "Skiing">
# re.match("sledding") # => #<Regex::MatchData "sledding">
# ```
def self.union(patterns : Enumerable(Regex | String)) : self
new patterns.map { |pattern| union_part pattern }.join('|')
end
# Union. Returns a `Regex` that matches any of *patterns*.
#
# All capture groups in the patterns after the first one will have their
# indexes offset.
#
# ```
# re = Regex.union(/skiing/i, "sledding")
# re.match("Skiing") # => #<Regex::MatchData "Skiing">
# re.match("sledding") # => #<Regex::MatchData "sledding">
# ```
def self.union(*patterns : Regex | String) : self
union patterns
end
private def self.union_part(pattern : Regex)
pattern.to_s
end
private def self.union_part(pattern : String)
escape pattern
end
# Union. Returns a `Regex` that matches either of the operands.
#
# All capture groups in the second operand will have their indexes
# offset.
#
# ```
# re = /skiing/i + /sledding/
# re.match("Skiing") # => #<Regex::MatchData "Skiing">
# re.match("sledding") # => #<Regex::MatchData "sledding">
# ```
def +(other)
Regex.union(self, other)
end
# Equality. Two regexes are equal if their sources and options are the same.
#
# ```
# /abc/ == /abc/i # => false
# /abc/i == /ABC/i # => false
# /abc/i == /abc/i # => true
# ```
def ==(other : Regex)
source == other.source && options == other.options
end
# Case equality. This is equivalent to `#match` or `#=~` but only returns
# `true` or `false`. Used in `case` expressions. The special variable
# `$~` will contain a `Regex::MatchData` if there was a match, `nil` otherwise.
#
# ```
# a = "HELLO"
# b = case a
# when /^[a-z]*$/
# "Lower case"
# when /^[A-Z]*$/
# "Upper case"
# else
# "Mixed case"
# end
# b # => "Upper case"
# ```
def ===(other : String)
match = match(other)
$~ = match
!match.nil?
end
# Match. Matches a regular expression against *other* and returns
# the starting position of the match if *other* is a matching `String`,
# otherwise `nil`. `$~` will contain a `Regex::MatchData` if there was a match,
# `nil` otherwise.
#
# ```
# /at/ =~ "input data" # => 7
# /ax/ =~ "input data" # => nil
# ```
def =~(other : String)
match = self.match(other)
$~ = match
match.try &.begin(0)
end
# Match. When the argument is not a `String`, always returns `nil`.
#
# ```
# /at/ =~ "input data" # => 7
# /ax/ =~ "input data" # => nil
# ```
def =~(other)
nil
end
# Convert to `String` in literal format. Returns the source as a `String` in
# Regex literal format, delimited in forward slashes (`/`), with any
# optional flags included.
#
# ```
# /ab+c/ix.inspect # => "/ab+c/ix"
# ```
def inspect(io : IO) : Nil
io << '/'
Regex.append_source(source, io)
io << '/'
io << 'i' if options.ignore_case?
io << 'm' if options.multiline?
io << 'x' if options.extended?
end
# Match at character index. Matches a regular expression against `String`
# *str*. Starts at the character index given by *pos* if given, otherwise at
# the start of *str*. Returns a `Regex::MatchData` if *str* matched, otherwise
# `nil`. `$~` will contain the same value that was returned.
#
# ```
# /(.)(.)(.)/.match("abc").try &.[2] # => "b"
# /(.)(.)/.match("abc", 1).try &.[2] # => "c"
# /(.)(.)/.match("クリスタル", 3).try &.[2] # => "ル"
# ```
def match(str, pos = 0, options = Regex::Options::None) : MatchData?
if byte_index = str.char_index_to_byte_index(pos)
match = match_at_byte_index(str, byte_index, options)
else
match = nil
end
$~ = match
end
# Match at byte index. Matches a regular expression against `String`
# *str*. Starts at the byte index given by *pos* if given, otherwise at
# the start of *str*. Returns a `Regex::MatchData` if *str* matched, otherwise
# `nil`. `$~` will contain the same value that was returned.
#
# ```
# /(.)(.)(.)/.match_at_byte_index("abc").try &.[2] # => "b"
# /(.)(.)/.match_at_byte_index("abc", 1).try &.[2] # => "c"
# /(.)(.)/.match_at_byte_index("クリスタル", 3).try &.[2] # => "ス"
# ```
def match_at_byte_index(str, byte_index = 0, options = Regex::Options::None) : MatchData?
return ($~ = nil) if byte_index > str.bytesize
ovector_size = (@captures + 1) * 3
ovector = Pointer(Int32).malloc(ovector_size)
ret = LibPCRE.exec(@re, @extra, str, str.bytesize, byte_index, (options | Options::NO_UTF8_CHECK), ovector, ovector_size)
if ret > 0
match = MatchData.new(self, @re, str, byte_index, ovector, @captures)
else
match = nil
end
$~ = match
end
# Returns a `Hash` where the values are the names of capture groups and the
# keys are their indexes. Non-named capture groups will not have entries in
# the `Hash`. Capture groups are indexed starting from `1`.
#
# ```
# /(.)/.name_table # => {}
# /(?<foo>.)/.name_table # => {1 => "foo"}
# /(?<foo>.)(?<bar>.)/.name_table # => {2 => "bar", 1 => "foo"}
# /(.)(?<foo>.)(.)(?<bar>.)(.)/.name_table # => {4 => "bar", 2 => "foo"}
# ```
def name_table : Hash(UInt16, String)
LibPCRE.full_info(@re, @extra, LibPCRE::INFO_NAMECOUNT, out name_count)
LibPCRE.full_info(@re, @extra, LibPCRE::INFO_NAMEENTRYSIZE, out name_entry_size)
table_pointer = Pointer(UInt8).null
LibPCRE.full_info(@re, @extra, LibPCRE::INFO_NAMETABLE, pointerof(table_pointer).as(Pointer(Int32)))
name_table = table_pointer.to_slice(name_entry_size*name_count)
lookup = Hash(UInt16, String).new
name_count.times do |i|
capture_offset = i * name_entry_size
capture_number = (name_table[capture_offset].to_u16 << 8) | name_table[capture_offset + 1].to_u16
name_offset = capture_offset + 2
checked = name_table[name_offset, name_entry_size - 3]
name = String.new(checked.to_unsafe)
lookup[capture_number] = name
end
lookup
end
# Convert to `String` in subpattern format. Produces a `String` which can be
# embedded in another `Regex` via interpolation, where it will be interpreted
# as a non-capturing subexpression in another regular expression.
#
# ```
# re = /A*/i # => /A*/i
# re.to_s # => "(?i-msx:A*)"
# "Crystal".match(/t#{re}l/) # => #<Regex::MatchData "tal">
# re = /A*/ # => "(?-imsx:A*)"
# "Crystal".match(/t#{re}l/) # => nil
# ```
def to_s(io : IO) : Nil
io << "(?"
io << 'i' if options.ignore_case?
io << "ms" if options.multiline?
io << 'x' if options.extended?
io << '-'
io << 'i' unless options.ignore_case?
io << "ms" unless options.multiline?
io << 'x' unless options.extended?
io << ':'
Regex.append_source(source, io)
io << ')'
end
# :nodoc:
def self.append_source(source, io) : Nil
reader = Char::Reader.new(source)
while reader.has_next?
case char = reader.current_char
when '\\'
io << '\\'
io << reader.next_char
when '/'
io << "\\/"
else
io << char
end
reader.next_char
end
end
def dup
self
end
def clone
self
end
end