-
Notifications
You must be signed in to change notification settings - Fork 17
/
lex.go
523 lines (475 loc) · 10 KB
/
lex.go
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
package expr
//go:generate stringer -type=tokenkind
import (
"fmt"
"io"
"strconv"
"unicode"
"unicode/utf8"
)
func lower(ch rune) rune {
return ('a' - 'A') | ch
}
func isdecimal(ch rune) bool {
return '0' <= ch && ch <= '9'
}
func isoctal(ch rune) bool {
return '0' <= ch && ch <= '7'
}
func ishex(ch rune) bool {
return '0' <= ch && ch <= '9' || 'a' <= lower(ch) && lower(ch) <= 'f'
}
func isletter(c rune) bool {
return 'a' <= lower(c) && lower(c) <= 'z' || c == '_' || c >= utf8.RuneSelf && unicode.IsLetter(c)
}
func isdigit(c rune) bool {
return isdecimal(c) || c >= utf8.RuneSelf && unicode.IsDigit(c)
}
func isnumber(c rune) bool {
return isdigit(c) || ishex(c) || c == '.' || lower(c) == 'x'
}
func isident(c rune) bool {
return isletter(c) || isdigit(c)
}
func iswhitespace(c rune) bool {
return c == ' ' || c == '\t'
}
// tokenkind is an enumeration of different kinds of tokens.
type tokenkind int
// This is a definition of all possible token kinds.
const (
niltoken tokenkind = iota
errtoken
eoftoken
identtoken
inttoken
floattoken
booltoken
strtoken
runetoken
addtoken
subtoken
multoken
quotoken
remtoken
andtoken
nottoken
ortoken
xortoken
shltoken
shrtoken
andnottoken
logicalandtoken
logicalortoken
equaltoken
lessertoken
greatertoken
notequaltoken
lesserequaltoken
greaterequaltoken
leftparentoken
leftbrackettoken
commatoken
periodtoken
rightparentoken
rightbrackettoken
colontoken
ternarytoken
boolkeyword
bytekeyword
float32keyword
float64keyword
intkeyword
int8keyword
int16keyword
int32keyword
int64keyword
uintkeyword
uint8keyword
uint16keyword
uint32keyword
uint64keyword
uintptrkeyword
nilkeyword
)
var keywordmap = map[string]tokenkind{
"bool": boolkeyword,
"byte": bytekeyword,
"float32": float32keyword,
"float64": float64keyword,
"int": intkeyword,
"int8": int8keyword,
"int16": int16keyword,
"int32": int32keyword,
"int64": int64keyword,
"uint": uintkeyword,
"uint8": uint8keyword,
"uint16": uint16keyword,
"uint32": uint32keyword,
"uint64": uint64keyword,
"uintptr": uintptrkeyword,
"nil": nilkeyword,
}
const eof = utf8.MaxRune + 0x0001
// token contains information for a single lexical token.
type token struct {
kind tokenkind
pos int
sval string
ival int64
uval uint64
fval float64
bval bool
sign bool
eval error
}
// scanner scans lexical tokens from the expression.
type scanner struct {
r io.RuneScanner
p int
eof bool
}
func newscanner(r io.RuneScanner) *scanner {
return &scanner{r: r}
}
func (s *scanner) readrune() rune {
if s.eof {
return eof
}
c, _, err := s.r.ReadRune()
if err == io.EOF {
s.eof = true
return eof
} else if err != nil {
panic(err)
}
s.p++
return c
}
func (s *scanner) unreadrune() {
if s.eof {
return
}
if err := s.r.UnreadRune(); err != nil {
panic(err)
}
s.p--
}
func (s *scanner) skipws() {
for {
c := s.readrune()
if !iswhitespace(c) {
s.unreadrune()
return
}
}
}
func (s *scanner) accept(c rune) bool {
if s.readrune() == c {
return true
}
s.unreadrune()
return false
}
func (s *scanner) expect(c rune) {
r := s.readrune()
if r != c {
panic(fmt.Errorf("expected %c", r))
}
}
func (s *scanner) peekmatch(f func(rune) bool) bool {
c := s.readrune()
s.unreadrune()
return f(c)
}
func (s *scanner) acceptfn(f func(rune) bool) (rune, bool) {
r := s.readrune()
if f(r) {
return r, true
}
s.unreadrune()
return r, false
}
func (s *scanner) expectfn(f func(rune) bool) rune {
r, ok := s.acceptfn(f)
if !ok {
panic(fmt.Errorf("unexpected %c", r))
}
return r
}
func (s *scanner) tokensym(k tokenkind, src string) token {
return token{kind: k, sval: src}
}
func (s *scanner) errsymf(format string, a ...interface{}) token {
return token{kind: errtoken, eval: fmt.Errorf(format, a...)}
}
func (s *scanner) scanident() token {
t := token{kind: identtoken}
if r, ok := s.acceptfn(isletter); ok {
t.sval = string(r)
} else {
return s.errsymf("unexpected ident start token: %c", r)
}
for {
if r, ok := s.acceptfn(isident); ok {
t.sval += string(r)
continue
}
break
}
// Handle boolean constant.
if t.sval == "true" {
t.kind = booltoken
t.bval = true
}
if t.sval == "false" {
t.kind = booltoken
t.bval = false
}
// Handle keywords.
if k, ok := keywordmap[t.sval]; ok {
t.kind = k
}
return t
}
func (s *scanner) scannumber(t token) token {
if r, ok := s.acceptfn(isnumber); ok {
t.sval += string(r)
} else {
return s.errsymf("unexpected int start token: %c", r)
}
for {
if r, ok := s.acceptfn(isnumber); ok {
t.sval += string(r)
continue
}
break
}
var err error
if t.uval, err = strconv.ParseUint(t.sval, 0, 64); err == nil {
t.ival = int64(t.uval)
t.fval = float64(t.ival)
t.kind = inttoken
t.sign = false
} else if t.ival, err = strconv.ParseInt(t.sval, 0, 64); err == nil {
t.uval = uint64(t.ival)
t.fval = float64(t.ival)
t.kind = inttoken
t.sign = true
} else if t.fval, err = strconv.ParseFloat(t.sval, 64); err == nil {
t.ival = int64(t.fval)
t.uval = uint64(t.fval)
t.kind = floattoken
} else {
return token{kind: errtoken, eval: err}
}
return t
}
func runebytes(r rune) []byte {
runebuf := [4]byte{}
l := utf8.EncodeRune(runebuf[:], rune(r))
return runebuf[:l]
}
func (s *scanner) scanescape(quote byte) []byte {
switch {
case s.accept('a'):
return []byte{'\a'}
case s.accept('b'):
return []byte{'\b'}
case s.accept('f'):
return []byte{'\f'}
case s.accept('n'):
return []byte{'\n'}
case s.accept('r'):
return []byte{'\r'}
case s.accept('t'):
return []byte{'\t'}
case s.accept('v'):
return []byte{'\v'}
case s.accept('\\'):
return []byte{'\\'}
case s.accept(rune(quote)):
return []byte{quote}
case s.peekmatch(isoctal):
octal := string([]rune{s.expectfn(isoctal), s.expectfn(isoctal), s.expectfn(isoctal)})
code, err := strconv.ParseUint(octal, 8, 8)
if err != nil {
panic(err)
}
return []byte{byte(code)}
case s.accept('x'):
hex := string([]rune{s.expectfn(ishex), s.expectfn(ishex)})
code, err := strconv.ParseUint(hex, 16, 8)
if err != nil {
panic(err)
}
return []byte{byte(code)}
case s.accept('u'):
hex := string([]rune{
s.expectfn(ishex), s.expectfn(ishex), s.expectfn(ishex), s.expectfn(ishex),
})
code, err := strconv.ParseUint(hex, 16, 16)
if err != nil {
panic(err)
}
return runebytes(rune(code))
case s.accept('U'):
hex := string([]rune{
s.expectfn(ishex), s.expectfn(ishex), s.expectfn(ishex), s.expectfn(ishex),
s.expectfn(ishex), s.expectfn(ishex), s.expectfn(ishex), s.expectfn(ishex),
})
code, err := strconv.ParseUint(hex, 16, 32)
if err != nil {
panic(err)
}
return runebytes(rune(code))
default:
panic(fmt.Errorf("unexpected escape code %c", s.readrune()))
}
}
func (s *scanner) scanstring(quote byte) token {
str := []byte{}
for {
switch {
case s.accept(rune(quote)):
return token{kind: strtoken, sval: string(str)}
case s.accept('\\'):
str = append(str, s.scanescape(quote)...)
default:
str = append(str, runebytes(s.readrune())...)
}
}
}
func (s *scanner) scanrune() token {
defer s.expect('\'')
switch {
case s.accept('\\'):
r := []rune(string(s.scanescape('\'')))
return token{kind: runetoken, ival: int64(r[0])}
default:
return token{kind: runetoken, ival: int64(s.readrune())}
}
}
func (s *scanner) scan() (t token) {
defer func() {
if r := recover(); r != nil {
if err, ok := r.(error); ok {
t = token{kind: errtoken, pos: s.p, eval: err}
} else {
panic(r)
}
}
}()
s.skipws()
p := s.p
defer func() {
t.pos = p
}()
switch {
case s.accept(eof):
p = s.p
return token{kind: eoftoken}
case s.peekmatch(isletter):
return s.scanident()
case s.peekmatch(isdigit):
return s.scannumber(token{})
case s.accept('"'):
return s.scanstring('"')
case s.accept('\''):
return s.scanrune()
case s.accept('$'):
s.expect('\'')
return s.scanstring('\'')
case s.accept('+'):
return s.tokensym(addtoken, "+")
case s.accept('-'):
switch {
default:
return s.tokensym(subtoken, "-")
case s.peekmatch(isdigit):
return s.scannumber(token{sval: "-"})
}
case s.accept('*'):
return s.tokensym(multoken, "*")
case s.accept('/'):
return s.tokensym(quotoken, "/")
case s.accept('%'):
return s.tokensym(remtoken, "%")
case s.accept('&'):
switch {
default:
return s.tokensym(andtoken, "&")
case s.accept('&'):
return s.tokensym(logicalandtoken, "&&")
case s.accept('^'):
return s.tokensym(andnottoken, "&^")
}
case s.accept('|'):
switch {
default:
return s.tokensym(ortoken, "|")
case s.accept('|'):
return s.tokensym(logicalortoken, "||")
}
case s.accept('^'):
switch {
default:
return s.tokensym(xortoken, "^")
}
case s.accept('<'):
switch {
default:
return s.tokensym(lessertoken, "<")
case s.accept('='):
return s.tokensym(lesserequaltoken, "<=")
case s.accept('<'):
return s.tokensym(shltoken, "<<")
}
case s.accept('>'):
switch {
default:
return s.tokensym(greatertoken, ">")
case s.accept('='):
return s.tokensym(greaterequaltoken, ">=")
case s.accept('>'):
return s.tokensym(shrtoken, ">>")
}
case s.accept('='):
switch {
case s.accept('='):
return s.tokensym(equaltoken, "==")
default:
return s.errsymf("unexpected rune %c", s.readrune())
}
case s.accept('!'):
switch {
case s.accept('='):
return s.tokensym(notequaltoken, "!=")
default:
return s.tokensym(nottoken, "!")
}
case s.accept('('):
return s.tokensym(leftparentoken, "(")
case s.accept('['):
return s.tokensym(leftbrackettoken, "[")
case s.accept(','):
return s.tokensym(commatoken, ",")
case s.accept('.'):
switch {
default:
return s.tokensym(periodtoken, ".")
case s.peekmatch(isdigit):
return s.scannumber(token{sval: "."})
}
case s.accept(')'):
return s.tokensym(rightparentoken, ")")
case s.accept(']'):
return s.tokensym(rightbrackettoken, "]")
case s.accept(':'):
return s.tokensym(colontoken, ":")
case s.accept('?'):
return s.tokensym(ternarytoken, "?")
default:
return s.errsymf("unexpected rune %c", s.readrune())
}
}