source: proto/matchparens/pdfparenmatch.pablo @ 5539

Last change on this file since 5539 was 3064, checked in by cameron, 6 years ago

Simplify parenthesis matching; fix paren match with comments.

File size: 1.7 KB
Line 
1#
2# Recursive Parenthesis Matching
3#
4#
5# Robert D. Cameron
6# October 14, 2012
7#
8
9class Basis_bits():     
10        bit_0 = 0
11        bit_1 = 0
12        bit_2 = 0
13        bit_3 = 0
14        bit_4 = 0
15        bit_5 = 0
16        bit_6 = 0
17        bit_7 = 0
18
19class Lex ():
20        LParen = 0
21        RParen = 0
22       
23class Matches() :
24        closed = 0
25        instring = 0
26        error = 0
27
28
29def Classify_bytes(basis_bits, lex): 
30        temp1 = (basis_bits.bit_0 | basis_bits.bit_1)
31        temp2 = (basis_bits.bit_2 &~ basis_bits.bit_3)
32        temp3 = (temp2 &~ temp1)
33        temp4 = (basis_bits.bit_4 &~ basis_bits.bit_5)
34        temp5 = (basis_bits.bit_6 | basis_bits.bit_7)
35        temp6 = (temp4 &~ temp5)
36        lex.LParen = (temp3 & temp6)
37        temp7 = (basis_bits.bit_7 &~ basis_bits.bit_6)
38        temp8 = (temp4 & temp7)
39        lex.RParen = (temp3 & temp8)
40       
41def Match_Parens(lex, matches):
42        parens = lex.LParen | lex.RParen
43        pscan = pablo.AdvanceThenScanTo(lex.LParen, parens)
44        matches.closed = pscan & lex.RParen
45        matches.instring = pablo.ExclusiveSpan(lex.LParen, pscan)
46        matches.error = pablo.atEOF(pscan)
47        # Not matched, still pending.
48        pending_LParen = pscan & lex.LParen
49        RParen_unmatched = lex.RParen &~ matches.closed
50        inPlay = pending_LParen | RParen_unmatched
51        while pending_LParen:
52                pscan = pablo.AdvanceThenScanTo(pending_LParen, inPlay)
53                matches.instring |= pablo.SpanUpTo(pending_LParen, pscan)
54                matches.closed |= pscan & lex.RParen
55                matches.error |= pablo.atEOF(pscan)
56                pending_LParen = pscan & lex.LParen
57                RParen_unmatched = lex.RParen &~ matches.closed
58                inPlay = pending_LParen | RParen_unmatched
59        #
60        # Any closing paren that was not actually used to close
61        # an opener is in error.
62        matches.error |= lex.RParen &~ matches.closed
63
64def Main(basis_bits, lex, matches):
65        Classify_bytes(basis_bits, lex)
66        Match_Parens(lex, matches)
67
68
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