JRegex

Regex Engine written by Java.

build

mvn clean package -Dorg.slf4j.simpleLogger.defaultLogLevel=info

Feature

• Regex => AST

RegexExp regexExp=RegexParser.parse("(a|b)*abb");
log.info(RegexExpTreeFormatter.format(regexExp));

[Concat]
├──[Repeat:*]
│  └──[Or]
│     ├──[Char:a]
│     └──[Char:b]
└──[Concat]
   ├──[Char:a]
   └──[Concat]
      ├──[Char:b]
      └──[Char:b]

• AST => NFA(thompson construction)

NFAGraph nfaGraph=NFAGraph.build(regexExp);
log.info(nfaGraph.toMermaidJsChart());

NFA Chart(using mermaid.js)

flowchart LR
    s_0(0) -->|ϵ| s_7(7)
    s_7(7) -->|ϵ| s_8(8)
    s_8(8) -->|'a'| s_9(9)
    s_9(9) -->|ϵ| s_10(10)
    s_10(10) -->|'b'| s_11(11)
    s_11(11) -->|ϵ| s_12(12)
    s_12(12) -->|'b'| s_13((13))
    s_0(0) -->|ϵ| s_1(1)
    s_1(1) -->|ϵ| s_4(4)
    s_4(4) -->|'b'| s_5(5)
    s_5(5) -->|ϵ| s_6(6)
    s_6(6) -->|ϵ| s_7(7)
    s_6(6) -->|ϵ| s_1(1)
    s_1(1) -->|ϵ| s_2(2)
    s_2(2) -->|'a'| s_3(3)
    s_3(3) -->|ϵ| s_6(6)

Loading

• NFA => DFA (Subset Construction)

DFAGraph dfa=nfa.toDFA();
log.info(dfa.toMermaidJsChart());
// state mappings
log.info(dfa.printStateMapping());

DFA Chart(using mermaid.js)

flowchart LR
    s_0(0) -->|'b'| s_4(4)
    s_4(4) -->|'b'| s_4(4)
    s_4(4) -->|'a'| s_1(1)
    s_1(1) -->|'b'| s_2(2)
    s_2(2) -->|'b'| s_3((3))
    s_3((3)) -->|'b'| s_4(4)
    s_3((3)) -->|'a'| s_1(1)
    s_2(2) -->|'a'| s_1(1)
    s_1(1) -->|'a'| s_1(1)
    s_0(0) -->|'a'| s_1(1)

Loading

state mappings

<<<<<<<<<<<< NFA -> DFA >>>>>>>>>>>>>
s_0<==>(s_7,s_8,s_0,s_1,s_2,s_4)
s_4<==>(s_5,s_6,s_7,s_8,s_1,s_2,s_4)
s_1<==>(s_6,s_7,s_8,s_9,s_10,s_1,s_2,s_3,s_4)
s_2<==>(s_5,s_6,s_7,s_8,s_11,s_12,s_1,s_2,s_4)
s_3<==>(s_5,s_6,s_7,s_8,s_13,s_1,s_2,s_4)

• DFA minimization

DFAGraph minDfa=dfa.simplify();
log.info(minDfa.toMermaidJsChart());
// state mappings
log.info(minDfa.printStateMapping());

min DFA state(using mermaid.js)

flowchart LR
    s_0(0) -->|'b'| s_0(0)
    s_0(0) -->|'a'| s_1(1)
    s_1(1) -->|'b'| s_2(2)
    s_2(2) -->|'b'| s_3((3))
    s_3((3)) -->|'b'| s_0(0)
    s_3((3)) -->|'a'| s_1(1)
    s_2(2) -->|'a'| s_1(1)
    s_1(1) -->|'a'| s_1(1)

Loading

state mappings

s_0<==>(s_0,s_4)
s_1<==>(s_1)
s_2<==>(s_2)
s_3<==>(s_3)

• NFA execution

void matches(){
    RegexExp regexExpression=RegexParser.parse("(a|b)*abb");
    NFAGraph nfa=NFAGraph.build(regexExpression);
    NFAGraphMatcher nfaGraphMatcher=new NFAGraphMatcher(nfa);
    Assertions.assertTrue(nfaGraphMatcher.matches("aaaaaaaaaaaaaaaaaaaaaabb"));
}

• DFA execution

void matches(){
    RegexExp regexExpression=RegexParser.parse("(a|b)*abb");
    NFAGraph nfa=NFAGraph.build(regexExpression);
    DFAGraph dfa=nfa.toDFA();
    DFAGraph minDfa=dfa.simplify();
    DFAGraphMatcher dfaGraphMatcher=new DFAGraphMatcher(minDfa);
    Assertions.assertTrue(dfaGraphMatcher.matches("aaaaaaaaaaaaaaaaaaaaaabb"));
}

Supported Syntax

• or |
• concat
• ()
• repeat
  • *
  • +
  • ?
  • {n,m}
  • {n}
  • {n,}
• char group
  • []
  • [^]
• char range
  • a-z
• single char(unicode char)
  • non-escaped char
  • escape char( escaped by \)
• meta char
  • \d \D => [0-9]
  • \w \W => [a-zA-Z0-9_]
  • \s \S => [ \t\n\x0B\f\r]
  • . => [all chars]