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package IO::Scalar;
=head1 NAME
IO::Scalar - IO:: interface for reading/writing a scalar
=head1 SYNOPSIS
Perform I/O on strings, using the basic OO interface...
use 5.005;
use IO::Scalar;
$data = "My message:\n";
### Open a handle on a string, and append to it:
$SH = new IO::Scalar \$data;
$SH->print("Hello");
$SH->print(", world!\nBye now!\n");
print "The string is now: ", $data, "\n";
### Open a handle on a string, read it line-by-line, then close it:
$SH = new IO::Scalar \$data;
while (defined($_ = $SH->getline)) {
print "Got line: $_";
}
$SH->close;
### Open a handle on a string, and slurp in all the lines:
$SH = new IO::Scalar \$data;
print "All lines:\n", $SH->getlines;
### Get the current position (either of two ways):
$pos = $SH->getpos;
$offset = $SH->tell;
### Set the current position (either of two ways):
$SH->setpos($pos);
$SH->seek($offset, 0);
### Open an anonymous temporary scalar:
$SH = new IO::Scalar;
$SH->print("Hi there!");
print "I printed: ", ${$SH->sref}, "\n"; ### get at value
Don't like OO for your I/O? No problem.
Thanks to the magic of an invisible tie(), the following now
works out of the box, just as it does with IO::Handle:
use 5.005;
use IO::Scalar;
$data = "My message:\n";
### Open a handle on a string, and append to it:
$SH = new IO::Scalar \$data;
print $SH "Hello";
print $SH ", world!\nBye now!\n";
print "The string is now: ", $data, "\n";
### Open a handle on a string, read it line-by-line, then close it:
$SH = new IO::Scalar \$data;
while (<$SH>) {
print "Got line: $_";
}
close $SH;
### Open a handle on a string, and slurp in all the lines:
$SH = new IO::Scalar \$data;
print "All lines:\n", <$SH>;
### Get the current position (WARNING: requires 5.6):
$offset = tell $SH;
### Set the current position (WARNING: requires 5.6):
seek $SH, $offset, 0;
### Open an anonymous temporary scalar:
$SH = new IO::Scalar;
print $SH "Hi there!";
print "I printed: ", ${$SH->sref}, "\n"; ### get at value
And for you folks with 1.x code out there: the old tie() style still works,
though this is I<unnecessary and deprecated>:
use IO::Scalar;
### Writing to a scalar...
my $s;
tie *OUT, 'IO::Scalar', \$s;
print OUT "line 1\nline 2\n", "line 3\n";
print "String is now: $s\n"
### Reading and writing an anonymous scalar...
tie *OUT, 'IO::Scalar';
print OUT "line 1\nline 2\n", "line 3\n";
tied(OUT)->seek(0,0);
while (<OUT>) {
print "Got line: ", $_;
}
Stringification works, too!
my $SH = new IO::Scalar \$data;
print $SH "Hello, ";
print $SH "world!";
print "I printed: $SH\n";
=head1 DESCRIPTION
This class is part of the IO::Stringy distribution;
see L<IO::Stringy> for change log and general information.
The IO::Scalar class implements objects which behave just like
IO::Handle (or FileHandle) objects, except that you may use them
to write to (or read from) scalars. These handles are
automatically tiehandle'd (though please see L<"WARNINGS">
for information relevant to your Perl version).
Basically, this:
my $s;
$SH = new IO::Scalar \$s;
$SH->print("Hel", "lo, "); ### OO style
$SH->print("world!\n"); ### ditto
Or this:
my $s;
$SH = tie *OUT, 'IO::Scalar', \$s;
print OUT "Hel", "lo, "; ### non-OO style
print OUT "world!\n"; ### ditto
Causes $s to be set to:
"Hello, world!\n"
=head1 PUBLIC INTERFACE
=cut
use Carp;
use strict;
use vars qw($VERSION @ISA);
use IO::Handle;
use 5.005;
### Stringification, courtesy of B. K. Oxley (binkley): :-)
use overload '""' => sub { ${*{$_[0]}->{SR}} };
use overload 'bool' => sub { 1 }; ### have to do this, so object is true!
### The package version, both in 1.23 style *and* usable by MakeMaker:
$VERSION = "2.110";
### Inheritance:
@ISA = qw(IO::Handle);
### This stuff should be got rid of ASAP.
require IO::WrapTie and push @ISA, 'IO::WrapTie::Slave' if ($] >= 5.004);
#==============================
=head2 Construction
=over 4
=cut
#------------------------------
=item new [ARGS...]
I<Class method.>
Return a new, unattached scalar handle.
If any arguments are given, they're sent to open().
=cut
sub new {
my $proto = shift;
my $class = ref($proto) || $proto;
my $self = bless \do { local *FH }, $class;
tie *$self, $class, $self;
$self->open(@_); ### open on anonymous by default
$self;
}
sub DESTROY {
shift->close;
}
#------------------------------
=item open [SCALARREF]
I<Instance method.>
Open the scalar handle on a new scalar, pointed to by SCALARREF.
If no SCALARREF is given, a "private" scalar is created to hold
the file data.
Returns the self object on success, undefined on error.
=cut
sub open {
my ($self, $sref) = @_;
### Sanity:
defined($sref) or do {my $s = ''; $sref = \$s};
(ref($sref) eq "SCALAR") or croak "open() needs a ref to a scalar";
### Setup:
*$self->{Pos} = 0; ### seek position
*$self->{SR} = $sref; ### scalar reference
$self;
}
#------------------------------
=item opened
I<Instance method.>
Is the scalar handle opened on something?
=cut
sub opened {
*{shift()}->{SR};
}
#------------------------------
=item close
I<Instance method.>
Disassociate the scalar handle from its underlying scalar.
Done automatically on destroy.
=cut
sub close {
my $self = shift;
%{*$self} = ();
1;
}
=back
=cut
#==============================
=head2 Input and output
=over 4
=cut
#------------------------------
=item flush
I<Instance method.>
No-op, provided for OO compatibility.
=cut
sub flush { "0 but true" }
#------------------------------
=item getc
I<Instance method.>
Return the next character, or undef if none remain.
=cut
sub getc {
my $self = shift;
### Return undef right away if at EOF; else, move pos forward:
return undef if $self->eof;
substr(${*$self->{SR}}, *$self->{Pos}++, 1);
}
#------------------------------
=item getline
I<Instance method.>
Return the next line, or undef on end of string.
Can safely be called in an array context.
Currently, lines are delimited by "\n".
=cut
sub getline {
my $self = shift;
### Return undef right away if at EOF:
return undef if $self->eof;
### Get next line:
my $sr = *$self->{SR};
my $i = *$self->{Pos}; ### Start matching at this point.
### Minimal impact implementation!
### We do the fast fast thing (no regexps) if using the
### classic input record separator.
### Case 1: $/ is undef: slurp all...
if (!defined($/)) {
*$self->{Pos} = length $$sr;
return substr($$sr, $i);
}
### Case 2: $/ is "\n": zoom zoom zoom...
elsif ($/ eq "\012") {
### Seek ahead for "\n"... yes, this really is faster than regexps.
my $len = length($$sr);
for (; $i < $len; ++$i) {
last if ord (substr ($$sr, $i, 1)) == 10;
}
### Extract the line:
my $line;
if ($i < $len) { ### We found a "\n":
$line = substr ($$sr, *$self->{Pos}, $i - *$self->{Pos} + 1);
*$self->{Pos} = $i+1; ### Remember where we finished up.
}
else { ### No "\n"; slurp the remainder:
$line = substr ($$sr, *$self->{Pos}, $i - *$self->{Pos});
*$self->{Pos} = $len;
}
return $line;
}
### Case 3: $/ is ref to int. Do fixed-size records.
### (Thanks to Dominique Quatravaux.)
elsif (ref($/)) {
my $len = length($$sr);
my $i = ${$/} + 0;
my $line = substr ($$sr, *$self->{Pos}, $i);
*$self->{Pos} += $i;
*$self->{Pos} = $len if (*$self->{Pos} > $len);
return $line;
}
### Case 4: $/ is either "" (paragraphs) or something weird...
### This is Graham's general-purpose stuff, which might be
### a tad slower than Case 2 for typical data, because
### of the regexps.
else {
pos($$sr) = $i;
### If in paragraph mode, skip leading lines (and update i!):
length($/) or
(($$sr =~ m/\G\n*/g) and ($i = pos($$sr)));
### If we see the separator in the buffer ahead...
if (length($/)
? $$sr =~ m,\Q$/\E,g ### (ordinary sep) TBD: precomp!
: $$sr =~ m,\n\n,g ### (a paragraph)
) {
*$self->{Pos} = pos $$sr;
return substr($$sr, $i, *$self->{Pos}-$i);
}
### Else if no separator remains, just slurp the rest:
else {
*$self->{Pos} = length $$sr;
return substr($$sr, $i);
}
}
}
#------------------------------
=item getlines
I<Instance method.>
Get all remaining lines.
It will croak() if accidentally called in a scalar context.
=cut
sub getlines {
my $self = shift;
wantarray or croak("can't call getlines in scalar context!");
my ($line, @lines);
push @lines, $line while (defined($line = $self->getline));
@lines;
}
#------------------------------
=item print ARGS...
I<Instance method.>
Print ARGS to the underlying scalar.
B<Warning:> this continues to always cause a seek to the end
of the string, but if you perform seek()s and tell()s, it is
still safer to explicitly seek-to-end before subsequent print()s.
=cut
sub print {
my $self = shift;
*$self->{Pos} = length(${*$self->{SR}} .= join('', @_) . (defined($\) ? $\ : ""));
1;
}
sub _unsafe_print {
my $self = shift;
my $append = join('', @_) . $\;
${*$self->{SR}} .= $append;
*$self->{Pos} += length($append);
1;
}
sub _old_print {
my $self = shift;
${*$self->{SR}} .= join('', @_) . $\;
*$self->{Pos} = length(${*$self->{SR}});
1;
}
#------------------------------
=item read BUF, NBYTES, [OFFSET]
I<Instance method.>
Read some bytes from the scalar.
Returns the number of bytes actually read, 0 on end-of-file, undef on error.
=cut
sub read {
my $self = $_[0];
my $n = $_[2];
my $off = $_[3] || 0;
my $read = substr(${*$self->{SR}}, *$self->{Pos}, $n);
$n = length($read);
*$self->{Pos} += $n;
($off ? substr($_[1], $off) : $_[1]) = $read;
return $n;
}
#------------------------------
=item write BUF, NBYTES, [OFFSET]
I<Instance method.>
Write some bytes to the scalar.
=cut
sub write {
my $self = $_[0];
my $n = $_[2];
my $off = $_[3] || 0;
my $data = substr($_[1], $off, $n);
$n = length($data);
$self->print($data);
return $n;
}
#------------------------------
=item sysread BUF, LEN, [OFFSET]
I<Instance method.>
Read some bytes from the scalar.
Returns the number of bytes actually read, 0 on end-of-file, undef on error.
=cut
sub sysread {
my $self = shift;
$self->read(@_);
}
#------------------------------
=item syswrite BUF, NBYTES, [OFFSET]
I<Instance method.>
Write some bytes to the scalar.
=cut
sub syswrite {
my $self = shift;
$self->write(@_);
}
=back
=cut
#==============================
=head2 Seeking/telling and other attributes
=over 4
=cut
#------------------------------
=item autoflush
I<Instance method.>
No-op, provided for OO compatibility.
=cut
sub autoflush {}
#------------------------------
=item binmode
I<Instance method.>
No-op, provided for OO compatibility.
=cut
sub binmode {}
#------------------------------
=item clearerr
I<Instance method.> Clear the error and EOF flags. A no-op.
=cut
sub clearerr { 1 }
#------------------------------
=item eof
I<Instance method.> Are we at end of file?
=cut
sub eof {
my $self = shift;
(*$self->{Pos} >= length(${*$self->{SR}}));
}
#------------------------------
=item seek OFFSET, WHENCE
I<Instance method.> Seek to a given position in the stream.
=cut
sub seek {
my ($self, $pos, $whence) = @_;
my $eofpos = length(${*$self->{SR}});
### Seek:
if ($whence == 0) { *$self->{Pos} = $pos } ### SEEK_SET
elsif ($whence == 1) { *$self->{Pos} += $pos } ### SEEK_CUR
elsif ($whence == 2) { *$self->{Pos} = $eofpos + $pos} ### SEEK_END
else { croak "bad seek whence ($whence)" }
### Fixup:
if (*$self->{Pos} < 0) { *$self->{Pos} = 0 }
if (*$self->{Pos} > $eofpos) { *$self->{Pos} = $eofpos }
return 1;
}
#------------------------------
=item sysseek OFFSET, WHENCE
I<Instance method.> Identical to C<seek OFFSET, WHENCE>, I<q.v.>
=cut
sub sysseek {
my $self = shift;
$self->seek (@_);
}
#------------------------------
=item tell
I<Instance method.>
Return the current position in the stream, as a numeric offset.
=cut
sub tell { *{shift()}->{Pos} }
#------------------------------
#
# use_RS [YESNO]
#
# I<Instance method.>
# Obey the curent setting of $/, like IO::Handle does?
# Default is false in 1.x, but cold-welded true in 2.x and later.
#
sub use_RS {
my ($self, $yesno) = @_;
carp "use_RS is deprecated and ignored; \$/ is always consulted\n";
}
#------------------------------
=item setpos POS
I<Instance method.>
Set the current position, using the opaque value returned by C<getpos()>.
=cut
sub setpos { shift->seek($_[0],0) }
#------------------------------
=item getpos
I<Instance method.>
Return the current position in the string, as an opaque object.
=cut
*getpos = \&tell;
#------------------------------
=item sref
I<Instance method.>
Return a reference to the underlying scalar.
=cut
sub sref { *{shift()}->{SR} }
#------------------------------
# Tied handle methods...
#------------------------------
# Conventional tiehandle interface:
sub TIEHANDLE {
((defined($_[1]) && UNIVERSAL::isa($_[1], "IO::Scalar"))
? $_[1]
: shift->new(@_));
}
sub GETC { shift->getc(@_) }
sub PRINT { shift->print(@_) }
sub PRINTF { shift->print(sprintf(shift, @_)) }
sub READ { shift->read(@_) }
sub READLINE { wantarray ? shift->getlines(@_) : shift->getline(@_) }
sub WRITE { shift->write(@_); }
sub CLOSE { shift->close(@_); }
sub SEEK { shift->seek(@_); }
sub TELL { shift->tell(@_); }
sub EOF { shift->eof(@_); }
#------------------------------------------------------------
1;
__END__
=back
=cut
=head1 WARNINGS
Perl's TIEHANDLE spec was incomplete prior to 5.005_57;
it was missing support for C<seek()>, C<tell()>, and C<eof()>.
Attempting to use these functions with an IO::Scalar will not work
prior to 5.005_57. IO::Scalar will not have the relevant methods
invoked; and even worse, this kind of bug can lie dormant for a while.
If you turn warnings on (via C<$^W> or C<perl -w>),
and you see something like this...
attempt to seek on unopened filehandle
...then you are probably trying to use one of these functions
on an IO::Scalar with an old Perl. The remedy is to simply
use the OO version; e.g.:
$SH->seek(0,0); ### GOOD: will work on any 5.005
seek($SH,0,0); ### WARNING: will only work on 5.005_57 and beyond
=head1 VERSION
$Id: Scalar.pm,v 1.6 2005/02/10 21:21:53 dfs Exp $
=head1 AUTHORS
=head2 Primary Maintainer
David F. Skoll (F<dfs@roaringpenguin.com>).
=head2 Principal author
Eryq (F<eryq@zeegee.com>).
President, ZeeGee Software Inc (F<http://www.zeegee.com>).
=head2 Other contributors
The full set of contributors always includes the folks mentioned
in L<IO::Stringy/"CHANGE LOG">. But just the same, special
thanks to the following individuals for their invaluable contributions
(if I've forgotten or misspelled your name, please email me!):
I<Andy Glew,>
for contributing C<getc()>.
I<Brandon Browning,>
for suggesting C<opened()>.
I<David Richter,>
for finding and fixing the bug in C<PRINTF()>.
I<Eric L. Brine,>
for his offset-using read() and write() implementations.
I<Richard Jones,>
for his patches to massively improve the performance of C<getline()>
and add C<sysread> and C<syswrite>.
I<B. K. Oxley (binkley),>
for stringification and inheritance improvements,
and sundry good ideas.
I<Doug Wilson,>
for the IO::Handle inheritance and automatic tie-ing.
=head1 SEE ALSO
L<IO::String>, which is quite similar but which was designed
more-recently and with an IO::Handle-like interface in mind,
so you could mix OO- and native-filehandle usage without using tied().
I<Note:> as of version 2.x, these classes all work like
their IO::Handle counterparts, so we have comparable
functionality to IO::String.
=cut