BibTex grammar for ANTLR - parsing

Question

I'm looking for a bibtex grammar in ANTLR to use in a hobby project. I don't want to spend my time for writing ANTLR grammar (this may take some time for me because it will involve a learning curve). So I'd appreciate for any pointers.
Note: I've found bibtex grammars for bison and yacc but couldn't find any for antlr.
Edit: As Bart pointed the I don't need to parse the preambles and tex in the quoted strings.

Answer 1

Here's a (very) rudimentary BibTex grammar that emits an AST (contrary to a simple parse tree):
grammar BibTex;
options {
output=AST;
ASTLabelType=CommonTree;
}
tokens {
BIBTEXFILE;
TYPE;
STRING;
PREAMBLE;
COMMENT;
TAG;
CONCAT;
}
//////////////////////////////// Parser rules ////////////////////////////////
parse
: (entry (Comma? entry)* Comma?)? EOF -> ^(BIBTEXFILE entry*)
;
entry
: Type Name Comma tags CloseBrace -> ^(TYPE Name tags)
| StringType Name Assign QuotedContent CloseBrace -> ^(STRING Name QuotedContent)
| PreambleType content CloseBrace -> ^(PREAMBLE content)
| CommentType -> ^(COMMENT CommentType)
;
tags
: (tag (Comma tag)* Comma?)? -> tag*
;
tag
: Name Assign content -> ^(TAG Name content)
;
content
: concatable (Concat concatable)* -> ^(CONCAT concatable+)
| Number
| BracedContent
;
concatable
: QuotedContent
| Name
;
//////////////////////////////// Lexer rules ////////////////////////////////
Assign
: '='
;
Concat
: '#'
;
Comma
: ','
;
CloseBrace
: '}'
;
QuotedContent
: '"' (~('\\' | '{' | '}' | '"') | '\\' . | BracedContent)* '"'
;
BracedContent
: '{' (~('\\' | '{' | '}') | '\\' . | BracedContent)* '}'
;
StringType
: '#' ('s'|'S') ('t'|'T') ('r'|'R') ('i'|'I') ('n'|'N') ('g'|'G') SP? '{'
;
PreambleType
: '#' ('p'|'P') ('r'|'R') ('e'|'E') ('a'|'A') ('m'|'M') ('b'|'B') ('l'|'L') ('e'|'E') SP? '{'
;
CommentType
: '#' ('c'|'C') ('o'|'O') ('m'|'M') ('m'|'M') ('e'|'E') ('n'|'N') ('t'|'T') SP? BracedContent
| '%' ~('\r' | '\n')*
;
Type
: '#' Letter+ SP? '{'
;
Number
: Digit+
;
Name
: Letter (Letter | Digit | ':' | '-')*
;
Spaces
: SP {skip();}
;
//////////////////////////////// Lexer fragments ////////////////////////////////
fragment Letter
: 'a'..'z'
| 'A'..'Z'
;
fragment Digit
: '0'..'9'
;
fragment SP
: (' ' | '\t' | '\r' | '\n' | '\f')+
;
(if you don't want the AST, remove all -> and everything to the right of it and remove both the options{...} and tokens{...} blocks)
which can be tested with the following class:
import org.antlr.runtime.*;
import org.antlr.runtime.tree.*;
import org.antlr.stringtemplate.*;
public class Main {
public static void main(String[] args) throws Exception {
// parse the file 'test.bib'
BibTexLexer lexer = new BibTexLexer(new ANTLRFileStream("test.bib"));
BibTexParser parser = new BibTexParser(new CommonTokenStream(lexer));
// you can use the following tree in your code
// see: http://www.antlr.org/api/Java/classorg_1_1antlr_1_1runtime_1_1tree_1_1_common_tree.html
CommonTree tree = (CommonTree)parser.parse().getTree();
// print a DOT tree of our AST
DOTTreeGenerator gen = new DOTTreeGenerator();
StringTemplate st = gen.toDOT(tree);
System.out.println(st);
}
}
and the following example Bib-input (file: test.bib):
#PREAMBLE{
"\newcommand{\noopsort}[1]{} "
# "\newcommand{\singleletter}[1]{#1} "
}
#string {
me = "Bart Kiers"
}
#ComMENt{some comments here}
% or some comments here
#article{mrx05,
auTHor = me # "Mr. X",
Title = {Something Great},
publisher = "nob" # "ody",
YEAR = 2005,
x = {{Bib}\TeX},
y = "{Bib}\TeX",
z = "{Bib}" # "\TeX",
},
#misc{ patashnik-bibtexing,
author = "Oren Patashnik",
title = "BIBTEXing",
year = "1988"
} % no comma here
#techreport{presstudy2002,
author = "Dr. Diessen, van R. J. and Drs. Steenbergen, J. F.",
title = "Long {T}erm {P}reservation {S}tudy of the {DNEP} {P}roject",
institution = "IBM, National Library of the Netherlands",
year = "2002",
month = "December",
}
Run the demo
If you now generate a parser & lexer from the grammar:
java -cp antlr-3.3.jar org.antlr.Tool BibTex.g
and compile all .java source files:
javac -cp antlr-3.3.jar *.java
and finally run the Main class:
*nix/MacOS
java -cp .:antlr-3.3.jar Main
Windows
java -cp .;antlr-3.3.jar Main
You'll see some output on your console which corresponds to the following AST:
(click the image to enlarge it, generated with graphviz-dev.appspot.com)
To emphasize: I did not properly test the grammar! I wrote it a while back and never really used it in any project.