下面根據ABNF的語法定義，逐條來定義ANBF語法元素類：
（一）首先來看rulelist：
rulelist = 1*( rule / (*c-wsp c-nl) )List<Rule> ruleList;（二）rule的定義
rule代表一條上下文無關文法規則，rule的定義是：
rule = rulename defined-as elements c-nl
; continues if next line starts
; with white space對於Rule類來說，rulename、defined-as、elements是有具體內容的，我們將其定義爲Rule類的成員即可，而c-nl只是分隔符，其具體內容（例如是一個空格還是兩個空格），對於Rule沒有影響，因此我們把Rule類定義爲：
/*
This file is one of the component a Context-free Grammar Parser Generator,
which accept a piece of text as the input, and generates a parser
for the inputted context-free grammar.
Copyright (C) 2013, Junbiao Pan (Email: [email protected])
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
public class Rule {
private RuleName ruleName;
public RuleName getRuleName() { return ruleName; }
private String definedAs;
public String getDefinedAs() { return definedAs; }
public void setDefinedAs(String definedAs) { this.definedAs = definedAs; }
private Elements elements;
public Elements getElements() { return elements; }
public Rule(RuleName ruleName, String definedAs, Elements elements) {
this.ruleName = ruleName;
this.definedAs = definedAs;
this.elements = elements;
}
}
defined-as = *c-wsp ("=" / "=/") *c-wsp
; basic rules definition and
; incremental alternatives（三）rulename的定義
不廢話了，直接上代碼：
/*
This file is one of the component a Context-free Grammar Parser Generator,
which accept a piece of text as the input, and generates a parser
for the inputted context-free grammar.
Copyright (C) 2013, Junbiao Pan (Email: [email protected])
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
public class RuleName implements Element {
private String prefix;
private String rulename;
public String toString() { return prefix + rulename; }
public RuleName(String rulename) {
this.prefix = "";
this.rulename = rulename;
}
public RuleName(String prefix, String rulename) {
this.prefix = prefix;
this.rulename = rulename;
}
}
（四）elements的定義
/*
This file is one of the component a Context-free Grammar Parser Generator,
which accept a piece of text as the input, and generates a parser
for the inputted context-free grammar.
Copyright (C) 2013, Junbiao Pan (Email: [email protected])
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
// elements = alternation *c-wsp
public class Elements {
private Alternation alternation;
public Alternation getAlternation() { return alternation; }
public Elements(Alternation alternation) {
this.alternation = alternation;
}
}
elements其實就是alternation，我把alternation定義爲elements的成員（而不是定義爲子類），主要是因爲elements比alternation多了後面的*c-wsp。
（五）Alternation的定義
/*
This file is one of the component a Context-free Grammar Parser Generator,
which accept a piece of text as the input, and generates a parser
for the inputted context-free grammar.
Copyright (C) 2013, Junbiao Pan (Email: [email protected])
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
// alternation = concatenation
// *(*c-wsp "/" *c-wsp concatenation)
public class Alternation {
private Set<Concatenation> concatenations = new HashSet<Concatenation>();
public void addConcatenation(Concatenation concatenation) {
concatenations.add(concatenation);
}
public Set<Concatenation> getConcatenations() {
return concatenations;
}
}
這裏把concatenation定義在集合Set而不是List中，是因爲alternation並無先後順序。
（六）Concatenation的定義
/*
This file is one of the component a Context-free Grammar Parser Generator,
which accept a piece of text as the input, and generates a parser
for the inputted context-free grammar.
Copyright (C) 2013, Junbiao Pan (Email: [email protected])
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
// concatenation = repetition *(1*c-wsp repetition)
public class Concatenation {
private List<Repetition> repetitions = new ArrayList<Repetition>();
public void addRepetition(Repetition repetition) {
repetitions.add(repetition);
}
public List<Repetition> getRepetitions() { return repetitions; }
}
一個concatenation由一個或多個repetition組成，這些repetition是有先後順序的。
（七）Repetition的定義
/*
This file is one of the component a Context-free Grammar Parser Generator,
which accept a piece of text as the input, and generates a parser
for the inputted context-free grammar.
Copyright (C) 2013, Junbiao Pan (Email: [email protected])
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
// repetition = [repeat] element
public class Repetition {
private Repeat repeat;
private Element element;
public Repetition(Repeat repeat, Element element) {
this.repeat = repeat;
this.element = element;
}
public Repetition(Element element) {
this(null, element);
}
}
/*
This file is one of the component a Context-free Grammar Parser Generator,
which accept a piece of text as the input, and generates a parser
for the inputted context-free grammar.
Copyright (C) 2013, Junbiao Pan (Email: [email protected])
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
// repeat = 1*DIGIT / (*DIGIT "*" *DIGIT)
public class Repeat {
private int min = 0, max = 0;
public int getMin() { return this.min; }
public int getMax() { return this.max; }
public Repeat(int min, int max) {this.min = min;this.max = max;}
}
再看element的定義：
// element = rulename / group / option /
// char-val / num-val / prose-val
public interface Element {
}（九）group的定義
/*
This file is one of the component a Context-free Grammar Parser Generator,
which accept a piece of text as the input, and generates a parser
for the inputted context-free grammar.
Copyright (C) 2013, Junbiao Pan (Email: [email protected])
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
// group = "(" *c-wsp alternation *c-wsp ")"
public class Group implements Element {
private Alternation alternation;
public Group(Alternation alternation) {this.alternation = alternation;}
}
（十）option的定義
/*
This file is one of the component a Context-free Grammar Parser Generator,
which accept a piece of text as the input, and generates a parser
for the inputted context-free grammar.
Copyright (C) 2013, Junbiao Pan (Email: [email protected])
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
// option = "[" *c-wsp alternation *c-wsp "]"
public class Option implements Element {
private Alternation alternation;
public Alternation getAlternation() { return alternation; }
public Option(Alternation alternation) {this.alternation = alternation;}
}
（十一）num_val的定義
num_val包括二進制、十進制和十六進制的形式。
/*
This file is one of the component a Context-free Grammar Parser Generator,
which accept a piece of text as the input, and generates a parser
for the inputted context-free grammar.
Copyright (C) 2013, Junbiao Pan (Email: [email protected])
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/*
num-val = "%" (bin-val / dec-val / hex-val)
bin-val = "b" 1*BIT
[ 1*("." 1*BIT) / ("-" 1*BIT) ]
; series of concatenated bit values
; or single ONEOF range
dec-val = "d" 1*DIGIT
[ 1*("." 1*DIGIT) / ("-" 1*DIGIT) ]
hex-val = "x" 1*HEXDIG
[ 1*("." 1*HEXDIG) / ("-" 1*HEXDIG) ]
*/
public class NumVal implements Element {//, Terminal {
private String base;
private List<String> values = new ArrayList<String>();
public List<String> getValues() { return values; }
public NumVal(String base) {
this.base = base;
}
}
無論是二進制、十進制還是十六進制，都有列舉和範圍兩種形式，例如%d11.22.33.44表示4個十進制的數字11、22、33、44，而%x00-ff表示十六進制從0x00到0xff之間。
這裏單獨定義範圍類型的數值：
/*
This file is one of the component a Context-free Grammar Parser Generator,
which accept a piece of text as the input, and generates a parser
for the inputted context-free grammar.
Copyright (C) 2013, Junbiao Pan (Email: [email protected])
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
public class RangedNumVal implements Element {
private String base, from ,to;
public RangedNumVal(String base, String from, String to) {
this.base = base;
this.from = from;
this.to = to;
}
}
（十二）char-val和prose-val
char-val和prose-val的ABNF定義：
char-val = DQUOTE *(%x20-21 / %x23-7E) DQUOTE
; quoted string of SP and VCHAR
without DQUOTE
prose-val = "<" *(%x20-3D / %x3F-7E) ">"
; bracketed string of SP and VCHAR
without angles
; prose description, to be used as
last resort/*
This file is one of the component a Context-free Grammar Parser Generator,
which accept a piece of text as the input, and generates a parser
for the inputted context-free grammar.
Copyright (C) 2013, Junbiao Pan (Email: [email protected])
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
public class CharVal implements Element {
private String value;
public CharVal(String value) {
this.value = value;
}
}
/*
This file is one of the component a Context-free Grammar Parser Generator,
which accept a piece of text as the input, and generates a parser
for the inputted context-free grammar.
Copyright (C) 2013, Junbiao Pan (Email: [email protected])
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
public class ProseVal implements Element {
private String value;
public ProseVal(String value) {
this.value = value;
}
}
有了這些元素對應的類定義，下一步我們就可以開始正式寫預測分析器的代碼了。
上面的版權聲明比較累贅，還請包涵，代碼會在完善的時候逐步加上去的。
午休去 :)
本系列文章索引：基於預測的ABNF文法分析器