btparse
(a C library to parse BibTeX files)
version 0.2
8 September, 1997
Greg Ward (greg@bic.mni.mcgill.ca)
Copyright (c) 1997 by Gregory P. Ward. All rights reserved.
This library is free software; you can redistribute it and/or modify it
under the terms of the GNU Library General Public License as published by
the Free Software Foundation; either version 2 of the License, or (at your
option) any later version.
This library 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 Library General Public
License for more details.
(Please note that this licence statement only covers the source files in
the top-level distribution directory. Source files in the "progs" and "t"
sub-directories are covered by either the GNU Library General Public
License (getopt.c, getopt1.c, and getopt.h, which come from the GNU C
Library) or the GNU General Public Licence (all other files, which were
written by me). The files in the "pccts" subdirectory are part of PCCTS
1.33, and were written (for the most part) by Terence Parr. They are *not*
covered by either GNU licence. In all cases, consult each file for the
appropriate copyright and licensing information.)
INTRODUCTION
------------
btparse is a C library for parsing and processing BibTeX files. Its
primary use is as the back-end to my Text::BibTeX module for Perl 5, but
there's nothing to prevent you from writing C programs using btparse (or
from writing extensions to other high-level languages using btparse as a
back-end). (Except, perhaps, that the documentation is a bit skimpy).
It is built on top of a lexical analyzer and parser constructed using PCCTS
(the Purdue Compiler Construction Tool Set), which provides efficient,
reliable parsing with excellent error detection, reporting, and recovery.
The library provides entry points to the parser, functions to traverse and
query the abstract-syntax tree that results, and some functions for
processing strings in "the BibTeX way". The only requirement for building
the library is an ANSI-compliant C compiler. In particular, you do *not*
need PCCTS, because enough of it is included in the distribution to build
btparse. (Of course, if you play with the grammar file (bibtex.g), then
you will need PCCTS to re-build the library. If you do this, though, you
probably know what you're doing and already have PCCTS.)
You can find the latest version of btparse (as well as its companion
Perl module, Text::BibTeX) at
ftp://ftp.bic.mni.mcgill.ca/pub/users/greg
as well as on any CPAN (Comprehensive Perl Archive Network) site, in
modules/by-authors/Greg_Ward/.
BUILDING
--------
To build the library (which you will have to do in any case, even if you
just want to use it through my Perl module), do the following:
1) Take a look in Makefile.defs; in particular, you might have to
change CC, OPT, ARFLAGS, and RANLIB, especially if you're running
an archaic OS such as SunOS.
2) Type `make lib'.
3) Type `make test'.
If anything goes wrong with the build process, double-check that your C
compiler is ANSI-compliant (if you're trying to use "cc" under SunOS or
Solaris, it isn't!). If you're sure that everything is in working order
at your end, feel free to email me.
If any of the tests fail, *please* contact me and let me know. It might
be helpful to run the test program manually (switch into the "t"
directory and run "simple_test"), as "make test" discards any error
messages.
If you're just doing this in order to build Text::BibTeX, you're done --
go back to the Text::BibTeX README for further instructions.
If you're building btparse for use in your own C programs, you might
want to install it and/or build a shared library. To install the
library:
4) Edit Makefile.dirs to reflect your preferred installation location.
5) Type `make install'.
`make install' will install the static library file (libbtparse.a), the
header file that you need to include in your programs to use btparse
(btparse.h), and the man pages from the "doc" directory.
To build a shared library on a modern, ELF-based system such as Linux,
IRIX 5+, or Solaris 2.x (?), just type `make shlib'. If this doesn't
work, you're on your own. You're also on your own when it comes to
installing the shared library; that's just too system dependent.
DOCUMENTATION
-------------
In the "doc" directory you will find some rudimentary man pages covering
btparse. Even if you're not planning on using the library from C, you
might be interested in the bt_language page, which covers the lexical
and syntactic grammars that btparse uses to parse BibTeX.
The documentation is written using the pod (plain ol' documentation)
format, but *roff-ready versions are included with the distribution.
These are the versions that will be installed by `make install'.
If you have Perl 5 installed, you can use one of the pod converters
supplied with it to read or print the documentation; try pod2text, pod2man,
pod2html, or pod2latex.
Otherwise, you can use nroff, troff, or groff to process the "man page"
versions of the documentation. For instance, "groff -Tps -man
doc/bt_language.3" will produce a PostScript version of the "bt_language"
entry, and "groff -Tascii -man doc/bt_language.3" will give you a text
version.
If you find the documentation useful and would like to see more, please
let me know.
EXAMPLE PROGRAMS
----------------
Included in the "progs" directory are two example programs, bibparse and
biblex. The former provides an example of a well-behaved, useful program
based on btparse; by default, it reads a series of BibTeX files (named on
the command line), parses them, and prints their data out in a form that is
dead easy to parse in almost any language. (I used this as a preliminary
to the full-blown Text::BibTeX Perl module; to parse BibTeX data, I just
opened a pipe reading the output of bibparse, and used simple Perl code to
parse the data.) bibparse uses GNU getopt, but I've included the necessary
files with the distribution so you shouldn't have any problems building it.
biblex is an example of what *not* to do; it rudely pokes into the
internals of both the library and the PCCTS-generated lexical scanner on
which it is based. It prints out the stream of tokens in a BibTeX file
according to my lexical grammar. Do *not* use this program as an example!
I found it useful in debugging the lexical analyzer and parser, and provide
it solely for your amusement.
Both of these programs are unsupported, under-commented, and
undocumented (apart from the above paragraphs). If you would like this
to change, tell me about it -- if nobody except me is interested in
them, then unsupported and undocumented they will remain.
BUGS
----
There is one known bug that probably isn't going to be fixed any time
soon: entries with a large number of fields (more than about 90, if each
field value is just a single string) will cause the parser to crash.
This is unavoidable due to the PCCTS-generated parser using
statically-allocated stacks for attributes and abstract-syntax tree
nodes. I could increase the static allocation, but that would just
decrease the likelihood of encountering the problem, not make it go
away. (Anyways, the only BibTeX file I've seen with anywhere near 90
fields in an entry is part of the test suite distributed with bibclean.
It's a long term goal to be able to handle this, but the design of PCCTS
1.x makes it pretty difficult.)
Any segmentation faults or bus errors from the library should be
considered bugs. They probably result from passing in bogus data, but I
do make an attempt to catch all such mistakes, and if I've missed any
I'd like to know about it.
Any memory leaks from the library are also a concern; as long as you are
conscientious about calling the cleanup functions (bt_free_ast() and
bt_cleanup()), then the library shouldn't leak.