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129 lines
2.9 KiB
Perl
129 lines
2.9 KiB
Perl
#
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package IO::Seekable;
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=head1 NAME
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IO::Seekable - supply seek based methods for I/O objects
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=head1 SYNOPSIS
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use IO::Seekable;
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package IO::Something;
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@ISA = qw(IO::Seekable);
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=head1 DESCRIPTION
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C<IO::Seekable> does not have a constructor of its own as it is intended to
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be inherited by other C<IO::Handle> based objects. It provides methods
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which allow seeking of the file descriptors.
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=over 4
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=item $io->getpos
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Returns an opaque value that represents the current position of the
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IO::File, or C<undef> if this is not possible (eg an unseekable stream such
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as a terminal, pipe or socket). If the fgetpos() function is available in
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your C library it is used to implements getpos, else perl emulates getpos
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using C's ftell() function.
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=item $io->setpos
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Uses the value of a previous getpos call to return to a previously visited
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position. Returns "0 but true" on success, C<undef> on failure.
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=back
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See L<perlfunc> for complete descriptions of each of the following
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supported C<IO::Seekable> methods, which are just front ends for the
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corresponding built-in functions:
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=over 4
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=item $io->seek ( POS, WHENCE )
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Seek the IO::File to position POS, relative to WHENCE:
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=over 8
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=item WHENCE=0 (SEEK_SET)
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POS is absolute position. (Seek relative to the start of the file)
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=item WHENCE=1 (SEEK_CUR)
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POS is an offset from the current position. (Seek relative to current)
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=item WHENCE=2 (SEEK_END)
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POS is an offset from the end of the file. (Seek relative to end)
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=back
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The SEEK_* constants can be imported from the C<Fcntl> module if you
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don't wish to use the numbers C<0> C<1> or C<2> in your code.
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Returns C<1> upon success, C<0> otherwise.
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=item $io->sysseek( POS, WHENCE )
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Similar to $io->seek, but sets the IO::File's position using the system
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call lseek(2) directly, so will confuse most perl IO operators except
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sysread and syswrite (see L<perlfunc> for full details)
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Returns the new position, or C<undef> on failure. A position
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of zero is returned as the string C<"0 but true">
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=item $io->tell
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Returns the IO::File's current position, or -1 on error.
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=back
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=head1 SEE ALSO
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L<perlfunc>,
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L<perlop/"I/O Operators">,
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L<IO::Handle>
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L<IO::File>
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=head1 HISTORY
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Derived from FileHandle.pm by Graham Barr E<lt>gbarr@pobox.comE<gt>
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=cut
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use 5.006_001;
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use Carp;
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use strict;
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our($VERSION, @EXPORT, @ISA);
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use IO::Handle ();
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# XXX we can't get these from IO::Handle or we'll get prototype
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# mismatch warnings on C<use POSIX; use IO::File;> :-(
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use Fcntl qw(SEEK_SET SEEK_CUR SEEK_END);
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require Exporter;
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@EXPORT = qw(SEEK_SET SEEK_CUR SEEK_END);
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@ISA = qw(Exporter);
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$VERSION = "1.10";
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$VERSION = eval $VERSION;
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sub seek {
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@_ == 3 or croak 'usage: $io->seek(POS, WHENCE)';
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seek($_[0], $_[1], $_[2]);
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}
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sub sysseek {
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@_ == 3 or croak 'usage: $io->sysseek(POS, WHENCE)';
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sysseek($_[0], $_[1], $_[2]);
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}
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sub tell {
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@_ == 1 or croak 'usage: $io->tell()';
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tell($_[0]);
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}
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1;
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