
=head1 NAME

Mail::Box::Parser - reading and writing messages

=head1 CLASS INHERITANCE

 Mail::Box::Parser
   is a Mail::Reporter

 Mail::Box::Parser is extended by
   Mail::Box::Parser::Perl

=head1 SYNOPSIS


=head1 DESCRIPTION

The Mail::Box::Parser manages the parsing of folders.  Usually, you won't
need to know anything about this module, except the options which are
involved with this code.

There are two implementations of this module planned:

=over 4

=item * Mail::Box::Parser::Perl

A slower parser which only uses plain Perl.  This module is a bit slower,
and does less checking and less recovery.

=item * Mail::Box::Parser::C

A fast parser written in C<C>.  However, this parser is still under
development.

=back

On the moment the C parser comes available, and a C compiler is available
on your system, it will be used automatically.

=head1 METHODS

=head2 Initiation

=over 4

=item B<new> OPTIONS

(Class method) 
Create a parser object which can handle one file.  For
mbox-like mailboxes, this object can be used to read a whole folder.  In
case of MH-like mailboxes, each message is contained in a single file,
so each message has its own parser object.

 OPTION               DEFAULT
 file                 undef
 filename             <required>
 log                  'WARNINGS'
 mode                 'r'
 trace                'WARNINGS'

=over 4

=item B<file> =E<gt> FILE-HANDLE

Any C<IO::File> or C<GLOB> which can be used to read the data from.  In
case this option is specified, the C<filename> is informational only.

=item B<filename> =E<gt> FILENAME

(Required) The name of the file to be read.

=item B<log> =E<gt> LEVEL

See Mail::Reporter::new(log)

=item B<mode> =E<gt> OPENMODE

File-open mode, which defaults to C<'r'>, which means `read-only'.
See C<perldoc -f open> for possible modes.  Only applicable 
when no C<file> is specified.

=item B<trace> =E<gt> LEVEL

See Mail::Reporter::new(trace)

=back

=back

=head2 The Parser

=over 4

=item B<defaultParserType> [CLASS]

(Class or Instance method) 
Returns the parser to be used to parse all subsequent
messages, possibly first setting the parser using the optional argument.
Usually, the parser is autodetected; the C<C>-based parser will be used
when it can be, and the Perl-based parser will be used otherwise.

The CLASS argument allows you to specify a package name to force a
particular parser to be used (such as your own custom parser). You have
to C<use> or C<require> the package yourself before calling this method
with an argument. The parser must be a sub-class of Mail::Box::Parser.

=item B<fileChanged> 

Returns whether the file which is parsed has changed after the last
time takeFileInfo() was called.

=item B<filename> 

Returns the name of the file this parser is working on.

=item B<restart> 

Restart the parser on a certain file, usually because the content has
changed.

=item B<start> OPTIONS

Start the parser by opening a file.

 OPTION               DEFAULT
 file                 undef

=over 4

=item B<file> =E<gt> FILEHANDLE|undef

The file is already open, for instance because the data must be read
from STDIN.

=back

=item B<stop> 

Stop the parser, which will include a close of the file.  The lock on the
folder will not be removed (is not the responsibility of the parser).

=item B<takeFileInfo> 

Capture some data about the file being parsed, to be compared later.

=back

=head2 Parsing

=over 4

=item B<bodyAsFile> FILEHANDLE [,CHARS [,LINES]]

Try to read one message-body from the file, and immediately write
it to the specified file-handle.  Optionally, the predicted number
of CHARacterS and/or LINES to be read can be supplied.  These values may be
C<undef> and may be wrong.

The return is a list of three scalars: the location of the body (begin
and end) and the number of lines in the body.

=item B<bodyAsList> [,CHARS [,LINES]]

Try to read one message-body from the file.  Optionally, the predicted number
of CHARacterS and/or LINES to be read can be supplied.  These values may be
C<undef> and may be wrong.

The return is a list of scalars, each containing one line (including
line terminator), preceded by two integers representing the location
in the file where this body started and ended.

=item B<bodyAsString> [,CHARS [,LINES]]

Try to read one message-body from the file.  Optionally, the predicted number
of CHARacterS and/or LINES to be read can be supplied.  These values may be
C<undef> and may be wrong.

The return is a list of three scalars, the location in the file
where the body starts, where the body ends, and the string containing the
whole body.

=item B<bodyDelayed> [,CHARS [,LINES]]

Try to read one message-body from the file, but the data is skipped.
Optionally, the predicted number of CHARacterS and/or LINES to be skipped
can be supplied.  These values may be C<undef> and may be wrong.

The return is a list of four scalars: the location of the body (begin and
end), the size of the body, and the number of lines in the body.  The
number of lines may be C<undef>.

=item B<filePosition> [POSITION]

Returns the location of the next byte to be used in the file which is
parsed.  When a POSITION is specified, the location in the file is
moved to the indicated spot first.

=item B<lineSeparator> 

Returns the character or characters which are used to separate lines
in the folder file.  This is based on the first line of the file.
UNIX systems use a single LF to separate lines.  Windows uses a CR and
a LF.  Mac uses CR.

=item B<popSeparator> 

Remove the last-pushed separator from the list which is maintained by the
parser.  This will return C<undef> when there is none left.

=item B<pushSeparator> STRING|REGEXP

Add a boundary line.  Separators tell the parser where to stop reading.
A famous separator is the C<From>-line, which is used in Mbox-like
folders to separate messages.  But also parts (I<attachments>) is a
message are divided by separators.

The specified STRING describes the start of the separator-line.  The
REGEXP can specify a more complicated format.

=item B<readHeader> 

Read the whole message-header and return it as list
C<< field => value, field => value >>.  Mind that some fields will
appear more than once.

The first element will represent the position in the file where the
header starts.  The follows the list of header field names and bodies.

Examples:

 my ($where, @header) = $parser->readHeader;

=item B<readSeparator> OPTIONS

Read the currently active separator (the last one which was pushed).  The
line (or C<undef>) is returned.  Blank-lines before the separator lines
are ignored.

The return are two scalars, where the first gives the location of the
separator in the file, and the second the line which is found as
separator.  A new separator is activated using the pushSeparator() method.

=back

=head2 Reading and Writing [internals]

=over 4

=item B<closeFile> 

Close the file which was being parsed.

=item B<openFile> ARGS

Open the file to be parsed.  ARGS is a ref-hash of options.

 OPTION               DEFAULT
 filename             <required>
 mode                 <required>

=over 4

=item B<filename> =E<gt> FILENAME

=item B<mode> =E<gt> STRING

=back

=back

=head2 Logging and Tracing

=over 4

=item B<defaultTrace> [LEVEL, [LEVEL]

See Mail::Reporter::defaultTrace()

=item B<errors> 

See Mail::Reporter::errors()

=item B<log> [LEVEL [,STRINGS]]

See Mail::Reporter::log()

=item B<report> [LEVEL]

See Mail::Reporter::report()

=item B<reportAll> [LEVEL]

See Mail::Reporter::reportAll()

=item B<trace> [LEVEL]

See Mail::Reporter::trace()

=item B<warnings> 

See Mail::Reporter::warnings()

=back

=head2 Other Methods

=over 4

=item B<AUTOLOAD> 

See Mail::Reporter::AUTOLOAD()

=item B<DESTROY> 

See Mail::Reporter::DESTROY()

=item B<inGlobalDestruction> 

See Mail::Reporter::inGlobalDestruction()

=item B<logPriority> LEVEL

See Mail::Reporter::logPriority()

=item B<logSettings> 

See Mail::Reporter::logSettings()

=item B<notImplemented> 

See Mail::Reporter::notImplemented()

=back

=head1 SEE ALSO

A good start to read is Mail::Box-Overview.
More documentation and a mailinglist are available from the project's
website at L<http://perl.overmeer.net/mailbox/>.

=head1 AUTHOR

Written by Mark Overmeer (L<mark@overmeer.net|mailto:mark@overmeer.net>)
with the help of many.  See the ChangeLog for details.

=head1 VERSION

This code is beta, version 2.037.

Copyright (c) 2001-2003 by the authors. All rights reserved.
This program is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.
