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