#------------------------------------------------------------------------------
# File:         RandomAccess.pod -- Documentation for File::RandomAccess
#
# Description:  Buffer to support random access reading of sequential file
#
# Legal:        Copyright (c) 2003-2019 Phil Harvey (phil at owl.phy.queensu.ca)
#               This library is free software; you can redistribute it and/or
#               modify it under the same terms as Perl itself.
#------------------------------------------------------------------------------

=head1 NAME

File::RandomAccess - Random access reads of sequential file or scalar

=head1 SYNOPSIS

    use File::RandomAccess;

    $raf = new File::RandomAccess(\*FILE, $disableSeekTest);

    $raf = new File::RandomAccess(\$data);

    $err = $raf->Seek($pos);
    $num = $raf->Read($buff, $bytes);

=head1 DESCRIPTION

Allows random access to sequential file by buffering the file if necessary.
Also allows access to data in memory to be accessed as if it were a file.

=head1 METHODS

=over 4

=item B<new>

Creates a new RandomAccess object given a file reference or
reference to data in memory.

    # Read from open file or pipe
    $raf = new File::RandomAccess(\*FILE);

    # Read from data in memory
    $raf = new File::RandomAccess(\$data);

=over 4

=item Inputs:

0) Reference to RandomAccess object or RandomAccess class name.

1) File reference or scalar reference.

2) Flag set if file is already random access (disables automatic SeekTest).

=item Returns:

Reference to RandomAccess object.

=back

=item B<SeekTest>

Performs test seek() on file to determine if buffering is necessary.  If
the seek() fails, then the file is buffered to allow random access.
B<SeekTest>() is automatically called from B<new> unless specified.

    $result = $raf->SeekTest();

=over 4

=item Inputs:

0) Reference to RandomAccess object.

=item Returns:

1 if seek test passed (ie. no buffering required).

=item Notes:

Must be called before any other i/o.

=back

=item B<Tell>

Get current position in file

    $pos = $raf->Tell();

=over 4

=item Inputs:

0) Reference to RandomAccess object.

=item Returns:

Current position in file

=back

=item B<Seek>

Seek to specified position in file.  When buffered, this doesn't quite
behave like seek() since it returns success even if you seek outside the
limits of the file.

    $success = $raf->Seek($pos, 0);

=over 4

=item Inputs:

0) Reference to RandomAccess object.

1) Position.

2) Whence (0=from start, 1=from cur pos, 2=from end).

=item Returns:

1 on success, 0 otherwise

=back

=item B<Read>

Read data from the file.

    $num = $raf->Read($buff, 1024);

=over 4

=item Inputs:

0) Reference to RandomAccess object.

1) Buffer.

2) Number of bytes to read.

=item Returns:

Number of bytes actually read.

=back

=item B<ReadLine>

Read a line from file (end of line is $/).

=over 4

=item Inputs:

0) Reference to RandomAccess object.

1) Buffer.

=item Returns:

Number of bytes read.

=back

=item B<Slurp>

Read whole file into buffer, without changing read pointer.

=over 4

=item Inputs:

0) Reference to RandomAccess object.

=item Returns:

Nothing.

=back

=item B<BinMode>

Set binary mode for file.

=over 4

=item Inputs:

0) Reference to RandomAccess object.

=item Returns:

Nothing.

=back

=item B<Close>

Close the file and free the buffer.

=over 4

=item Inputs:

0) Reference to RandomAccess object.

=item Returns:

Nothing.

=back

=back

=head1 OPTIONS

=over 4

=item B<NoBuffer>

Avoid buffering sequential files.

    $raf->{NoBuffer} = 1;

When this option is set, old data is purged from the internal buffer before
a read operation on a sequential file.  In this mode, memory requirements
may be significantly reduced when reading sequential files, but seeking
backward is limited to within the size of the internal buffer (which will be
at least as large as the last returned data block), and seeking relative to
the end of file is not allowed.

=back

=head1 AUTHOR

Copyright 2003-2019 Phil Harvey (phil at owl.phy.queensu.ca)

This library is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.

=head1 SEE ALSO

L<Image::ExifTool(3pm)|Image::ExifTool>

=cut

# end
