NAME

       Mail::Mbox::MessageParser - A fast and simple mbox folder reader

SYNOPSIS

         #!/usr/bin/perl

         use Mail::Mbox::MessageParser;

         # Compression support
         my $file_name = 'mail/saved-mail.xz';
         my $file_handle = new FileHandle($file_name);

         # Set up cache. (Not necessary if enable_cache is false.)
         Mail::Mbox::MessageParser::SETUP_CACHE(
           { 'file_name' => '/tmp/cache' } );

         my $folder_reader =
           new Mail::Mbox::MessageParser( {
             'file_name' => $file_name,
             'file_handle' => $file_handle,
             'enable_cache' => 1,
             'enable_grep' => 1,
           } );

         die $folder_reader unless ref $folder_reader;

         # Any newlines or such before the start of the first email
         my $prologue = $folder_reader->prologue;
         print $prologue;

         # This is the main loop. It's executed once for each email
         while(!$folder_reader->end_of_file())
         {
           my $email = $folder_reader->read_next_email();
           print $$email;
         }

DESCRIPTION

       This module implements a fast but simple mbox folder reader. One of three implementations
       (Cache, Grep, Perl) will be used depending on the wishes of the user and the system
       configuration. The first implementation is a cached-based one which stores email
       information about mailboxes on the file system.  Subsequent accesses will be faster
       because no analysis of the mailbox will be needed. The second implementation is one based
       on GNU grep, and is significantly faster than the Perl version for mailboxes which contain
       very large (10MB) emails. The final implementation is a fast Perl-based one which should
       always be applicable.

       The Cache implementation is about 6 times faster than the standard Perl implementation.
       The Grep implementation is about 4 times faster than the standard Perl implementation. If
       you have GNU grep, it's best to enable both the Cache and Grep implementations. If the
       cache information is available, you'll get very fast speeds. Otherwise, you'll take about
       a 1/3 performance hit when the Grep version is used instead.

       The overriding requirement for this module is speed. If you wish more sophisticated
       parsing, use Mail::MboxParser (which is based on this module) or Mail::Box.

   METHODS AND FUNCTIONS
       SETUP_CACHE(...)
             SETUP_CACHE( { 'file_name' => <cache file name> } );

             <cache file name> - the file name of the cache

           Call this function once to set up the cache before creating any parsers. You must
           provide the location to the cache file. There is no default value.

       new(...)
             new( { 'file_name' => <mailbox file name>,
               'file_handle' => <mailbox file handle>,
               'enable_cache' => <1 or 0>,
               'enable_grep' => <1 or 0>,
               'force_processing' => <1 or 0>,
               'debug' => <1 or 0>,
             } );

             <mailbox file name> - the file name of the mailbox
             <mailbox file handle> - the already opened file handle for the mailbox
             <enable_cache> - true to attempt to use the cache implementation
             <enable_grep> - true to attempt to use the grep implementation
             <force_processing> - true to force processing of files that look invalid
             <debug> - true to print some debugging information to STDERR

           The constructor takes either a file name or a file handle, or both. If the file handle
           is not defined, Mail::Mbox::MessageParser will attempt to open the file using the file
           name. You should always pass the file name if you have it, so that the parser can
           cache the mailbox information.

           This module will automatically decompress the mailbox as necessary. If a filename is
           available but the file handle is undef, the module will call bzip, bzip2, gzip, lzip,
           xz to decompress the file in memory if the filename ends with the appropriate suffix.
           If the file handle is defined, it will detect the type of compression and apply the
           correct decompression program.

           The Cache, Grep, or Perl implementation of the parser will be loaded, whichever is
           most appropriate. For example, the first time you use caching, there will be no cache.
           In this case, the grep implementation can be used instead. The cache will be updated
           in memory as the grep implementation parses the mailbox, and the cache will be written
           after the program exits. The file name is optional, in which case enable_cache and
           enable_grep must both be false.

           force_processing will cause the module to process folders that look to be binary, or
           whose text data doesn't look like a mailbox.

           Returns a reference to a Mail::Mbox::MessageParser object on success, and a scalar
           desribing an error on failure. ("Not a mailbox", "Can't open <filename>: <system
           error>", "Can't execute <uncompress command> for file <filename>"

       reset()
           Reset the filehandle and all internal state. Note that this will not work with
           filehandles which are streams. If there is enough demand, I may add the ability to
           store the previously read stream data internally so that reset() will work correctly.

       endline()
           Returns "\n" or "\r\n", depending on the file format.

       prologue()
           Returns any newlines or other content at the start of the mailbox prior to the first
           email.

       end_of_file()
           Returns true if the end of the file has been encountered.

       line_number()
           Returns the line number for the start of the last email read.

       number()
           Returns the number of the last email read. (i.e. The first email will have a number of
           1.)

       length()
           Returns the length of the last email read.

       offset()
           Returns the byte offset of the last email read.

       read_next_email()
           Returns a reference to a scalar holding the text of the next email in the mailbox, or
           undef at the end of the file.

BUGS

       No known bugs.

       Contact david@coppit.org for bug reports and suggestions.

AUTHOR

       David Coppit <david@coppit.org>.

LICENSE

       This code is distributed under the GNU General Public License (GPL) Version 2.  See the
       file LICENSE in the distribution for details.

HISTORY

       This code was originally part of the grepmail distribution. See http://grepmail.sf.net/
       for previous versions of grepmail which included early versions of this code.

SEE ALSO

       Mail::MboxParser, Mail::Box