--- /dev/null
+.\" Automatically generated by Pod::Man v1.37, Pod::Parser v1.3
+.\"
+.\" Standard preamble:
+.\" ========================================================================
+.de Sh \" Subsection heading
+.br
+.if t .Sp
+.ne 5
+.PP
+\fB\\$1\fR
+.PP
+..
+.de Sp \" Vertical space (when we can't use .PP)
+.if t .sp .5v
+.if n .sp
+..
+.de Vb \" Begin verbatim text
+.ft CW
+.nf
+.ne \\$1
+..
+.de Ve \" End verbatim text
+.ft R
+.fi
+..
+.\" Set up some character translations and predefined strings. \*(-- will
+.\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left
+.\" double quote, and \*(R" will give a right double quote. | will give a
+.\" real vertical bar. \*(C+ will give a nicer C++. Capital omega is used to
+.\" do unbreakable dashes and therefore won't be available. \*(C` and \*(C'
+.\" expand to `' in nroff, nothing in troff, for use with C<>.
+.tr \(*W-|\(bv\*(Tr
+.ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p'
+.ie n \{\
+. ds -- \(*W-
+. ds PI pi
+. if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch
+. if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch
+. ds L" ""
+. ds R" ""
+. ds C` ""
+. ds C' ""
+'br\}
+.el\{\
+. ds -- \|\(em\|
+. ds PI \(*p
+. ds L" ``
+. ds R" ''
+'br\}
+.\"
+.\" If the F register is turned on, we'll generate index entries on stderr for
+.\" titles (.TH), headers (.SH), subsections (.Sh), items (.Ip), and index
+.\" entries marked with X<> in POD. Of course, you'll have to process the
+.\" output yourself in some meaningful fashion.
+.if \nF \{\
+. de IX
+. tm Index:\\$1\t\\n%\t"\\$2"
+..
+. nr % 0
+. rr F
+.\}
+.\"
+.\" For nroff, turn off justification. Always turn off hyphenation; it makes
+.\" way too many mistakes in technical documents.
+.hy 0
+.if n .na
+.\"
+.\" Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2).
+.\" Fear. Run. Save yourself. No user-serviceable parts.
+. \" fudge factors for nroff and troff
+.if n \{\
+. ds #H 0
+. ds #V .8m
+. ds #F .3m
+. ds #[ \f1
+. ds #] \fP
+.\}
+.if t \{\
+. ds #H ((1u-(\\\\n(.fu%2u))*.13m)
+. ds #V .6m
+. ds #F 0
+. ds #[ \&
+. ds #] \&
+.\}
+. \" simple accents for nroff and troff
+.if n \{\
+. ds ' \&
+. ds ` \&
+. ds ^ \&
+. ds , \&
+. ds ~ ~
+. ds /
+.\}
+.if t \{\
+. ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u"
+. ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u'
+. ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'^\h'|\\n:u'
+. ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u'
+. ds ~ \\k:\h'-(\\n(.wu-\*(#H-.1m)'~\h'|\\n:u'
+. ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u'
+.\}
+. \" troff and (daisy-wheel) nroff accents
+.ds : \\k:\h'-(\\n(.wu*8/10-\*(#H+.1m+\*(#F)'\v'-\*(#V'\z.\h'.2m+\*(#F'.\h'|\\n:u'\v'\*(#V'
+.ds 8 \h'\*(#H'\(*b\h'-\*(#H'
+.ds o \\k:\h'-(\\n(.wu+\w'\(de'u-\*(#H)/2u'\v'-.3n'\*(#[\z\(de\v'.3n'\h'|\\n:u'\*(#]
+.ds d- \h'\*(#H'\(pd\h'-\w'~'u'\v'-.25m'\f2\(hy\fP\v'.25m'\h'-\*(#H'
+.ds D- D\\k:\h'-\w'D'u'\v'-.11m'\z\(hy\v'.11m'\h'|\\n:u'
+.ds th \*(#[\v'.3m'\s+1I\s-1\v'-.3m'\h'-(\w'I'u*2/3)'\s-1o\s+1\*(#]
+.ds Th \*(#[\s+2I\s-2\h'-\w'I'u*3/5'\v'-.3m'o\v'.3m'\*(#]
+.ds ae a\h'-(\w'a'u*4/10)'e
+.ds Ae A\h'-(\w'A'u*4/10)'E
+. \" corrections for vroff
+.if v .ds ~ \\k:\h'-(\\n(.wu*9/10-\*(#H)'\s-2\u~\d\s+2\h'|\\n:u'
+.if v .ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'\v'-.4m'^\v'.4m'\h'|\\n:u'
+. \" for low resolution devices (crt and lpr)
+.if \n(.H>23 .if \n(.V>19 \
+\{\
+. ds : e
+. ds 8 ss
+. ds o a
+. ds d- d\h'-1'\(ga
+. ds D- D\h'-1'\(hy
+. ds th \o'bp'
+. ds Th \o'LP'
+. ds ae ae
+. ds Ae AE
+.\}
+.rm #[ #] #H #V #F C
+.\" ========================================================================
+.\"
+.IX Title "IO::WrapTie 3"
+.TH IO::WrapTie 3 "2005-02-10" "perl v5.8.7" "User Contributed Perl Documentation"
+.SH "NAME"
+IO::WrapTie \- wrap tieable objects in IO::Handle interface
+.PP
+\&\fIThis is currently Alpha code, released for comments.
+ Please give me your feedback!\fR
+.SH "SYNOPSIS"
+.IX Header "SYNOPSIS"
+First of all, you'll need \fItie()\fR, so:
+.PP
+.Vb 1
+\& require 5.004;
+.Ve
+.PP
+\&\fIFunction interface (experimental).\fR
+Use this with any existing class...
+.PP
+.Vb 2
+\& use IO::WrapTie;
+\& use FooHandle; ### implements TIEHANDLE interface
+.Ve
+.PP
+.Vb 2
+\& ### Suppose we want a "FooHandle\->new(&FOO_RDWR, 2)".
+\& ### We can instead say...
+.Ve
+.PP
+.Vb 1
+\& $FH = wraptie('FooHandle', &FOO_RDWR, 2);
+.Ve
+.PP
+.Vb 3
+\& ### Now we can use...
+\& print $FH "Hello, "; ### traditional operator syntax...
+\& $FH\->print("world!\en"); ### ...and OO syntax as well!
+.Ve
+.PP
+\&\fI\s-1OO\s0 interface (preferred).\fR
+You can inherit from the IO::WrapTie::Slave mixin to get a
+nifty \f(CW\*(C`new_tie()\*(C'\fR constructor...
+.PP
+.Vb 2
+\& #\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-
+\& package FooHandle; ### a class which can TIEHANDLE
+.Ve
+.PP
+.Vb 3
+\& use IO::WrapTie;
+\& @ISA = qw(IO::WrapTie::Slave); ### inherit new_tie()
+\& ...
+.Ve
+.PP
+.Vb 2
+\& #\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-
+\& package main;
+.Ve
+.PP
+.Vb 3
+\& $FH = FooHandle\->new_tie(&FOO_RDWR, 2); ### $FH is an IO::WrapTie::Master
+\& print $FH "Hello, "; ### traditional operator syntax
+\& $FH\->print("world!\en"); ### OO syntax
+.Ve
+.PP
+See IO::Scalar as an example. It also shows you how to create classes
+which work both with and without 5.004.
+.SH "DESCRIPTION"
+.IX Header "DESCRIPTION"
+Suppose you have a class \f(CW\*(C`FooHandle\*(C'\fR, where...
+.IP "\(bu" 4
+\&\fBFooHandle does not inherit from IO::Handle;\fR that is, it performs
+filehandle-like I/O, but to something other than an underlying
+file descriptor. Good examples are IO::Scalar (for printing to a
+string) and IO::Lines (for printing to an array of lines).
+.IP "\(bu" 4
+\&\fBFooHandle implements the \s-1TIEHANDLE\s0 interface\fR (see perltie);
+that is, it provides methods \s-1TIEHANDLE\s0, \s-1GETC\s0, \s-1PRINT\s0, \s-1PRINTF\s0,
+\&\s-1READ\s0, and \s-1READLINE\s0.
+.IP "\(bu" 4
+\&\fBFooHandle implements the traditional \s-1OO\s0 interface\fR of
+FileHandle and IO::Handle; i.e., it contains methods like \fIgetline()\fR,
+\&\fIread()\fR, \fIprint()\fR, \fIseek()\fR, \fItell()\fR, \fIeof()\fR, etc.
+.PP
+Normally, users of your class would have two options:
+.IP "\(bu" 4
+\&\fBUse only \s-1OO\s0 syntax,\fR and forsake named I/O operators like 'print'.
+.IP "\(bu" 4
+\&\fBUse with tie,\fR and forsake treating it as a first-class object
+(i.e., class-specific methods can only be invoked through the underlying
+object via \fItied()\fR... giving the object a \*(L"split personality\*(R").
+.PP
+But now with IO::WrapTie, you can say:
+.PP
+.Vb 4
+\& $WT = wraptie('FooHandle', &FOO_RDWR, 2);
+\& $WT\->print("Hello, world\en"); ### OO syntax
+\& print $WT "Yes!\en"; ### Named operator syntax too!
+\& $WT\->weird_stuff; ### Other methods!
+.Ve
+.PP
+And if you're authoring a class like FooHandle, just have it inherit
+from \f(CW\*(C`IO::WrapTie::Slave\*(C'\fR and that first line becomes even prettier:
+.PP
+.Vb 1
+\& $WT = FooHandle\->new_tie(&FOO_RDWR, 2);
+.Ve
+.PP
+\&\fBThe bottom line:\fR now, almost any class can look and work exactly like
+an IO::Handle... and be used both with \s-1OO\s0 and non-OO filehandle syntax.
+.SH "HOW IT ALL WORKS"
+.IX Header "HOW IT ALL WORKS"
+.Sh "The data structures"
+.IX Subsection "The data structures"
+Consider this example code, using classes in this distribution:
+.PP
+.Vb 2
+\& use IO::Scalar;
+\& use IO::WrapTie;
+.Ve
+.PP
+.Vb 3
+\& $WT = wraptie('IO::Scalar',\e$s);
+\& print $WT "Hello, ";
+\& $WT\->print("world!\en");
+.Ve
+.PP
+In it, the \fIwraptie()\fR function creates a data structure as follows:
+.PP
+.Vb 24
+\& * $WT is a blessed reference to a tied filehandle
+\& $WT glob; that glob is tied to the "Slave" object.
+\& | * You would do all your i/o with $WT directly.
+\& |
+\& |
+\& | ,\-\-\-isa\-\-> IO::WrapTie::Master >\-\-isa\-\-> IO::Handle
+\& V /
+\& .\-\-\-\-\-\-\-\-\-\-\-\-\-.
+\& | |
+\& | | * Perl i/o operators work on the tied object,
+\& | "Master" | invoking the TIEHANDLE methods.
+\& | | * Method invocations are delegated to the tied
+\& | | slave.
+\& `\-\-\-\-\-\-\-\-\-\-\-\-\-'
+\& |
+\& tied(*$WT) | .\-\-\-isa\-\-> IO::WrapTie::Slave
+\& V /
+\& .\-\-\-\-\-\-\-\-\-\-\-\-\-.
+\& | |
+\& | "Slave" | * Instance of FileHandle\-like class which doesn't
+\& | | actually use file descriptors, like IO::Scalar.
+\& | IO::Scalar | * The slave can be any kind of object.
+\& | | * Must implement the TIEHANDLE interface.
+\& `\-\-\-\-\-\-\-\-\-\-\-\-\-'
+.Ve
+.PP
+\&\fI\s-1NOTE:\s0\fR just as an IO::Handle is really just a blessed reference to a
+\&\fItraditional\fR filehandle glob... so also, an IO::WrapTie::Master
+is really just a blessed reference to a filehandle
+glob \fIwhich has been tied to some \*(L"slave\*(R" class.\fR
+.Sh "How \fIwraptie()\fP works"
+.IX Subsection "How wraptie() works"
+.IP "1." 4
+The call to function \f(CW\*(C`wraptie(SLAVECLASS, TIEARGS...)\*(C'\fR is
+passed onto \f(CW\*(C`IO::WrapTie::Master::new()\*(C'\fR.
+Note that class IO::WrapTie::Master is a subclass of IO::Handle.
+.IP "2." 4
+The \f(CW\*(C`IO::WrapTie::Master::new\*(C'\fR method creates a new IO::Handle object,
+reblessed into class IO::WrapTie::Master. This object is the \fImaster\fR,
+which will be returned from the constructor. At the same time...
+.IP "3." 4
+The \f(CW\*(C`new\*(C'\fR method also creates the \fIslave\fR: this is an instance
+of \s-1SLAVECLASS\s0 which is created by tying the master's IO::Handle
+to \s-1SLAVECLASS\s0 via \f(CW\*(C`tie(HANDLE, SLAVECLASS, TIEARGS...)\*(C'\fR.
+This call to \f(CW\*(C`tie()\*(C'\fR creates the slave in the following manner:
+.IP "4." 4
+Class \s-1SLAVECLASS\s0 is sent the message \f(CW\*(C`TIEHANDLE(TIEARGS...)\*(C'\fR; it
+will usually delegate this to \f(CW\*(C`SLAVECLASS::new(TIEARGS...)\*(C'\fR, resulting
+in a new instance of \s-1SLAVECLASS\s0 being created and returned.
+.IP "5." 4
+Once both master and slave have been created, the master is returned
+to the caller.
+.Sh "How I/O operators work (on the master)"
+.IX Subsection "How I/O operators work (on the master)"
+Consider using an i/o operator on the master:
+.PP
+.Vb 1
+\& print $WT "Hello, world!\en";
+.Ve
+.PP
+Since the master ($WT) is really a [blessed] reference to a glob,
+the normal Perl i/o operators like \f(CW\*(C`print\*(C'\fR may be used on it.
+They will just operate on the symbol part of the glob.
+.PP
+Since the glob is tied to the slave, the slave's \s-1PRINT\s0 method
+(part of the \s-1TIEHANDLE\s0 interface) will be automatically invoked.
+.PP
+If the slave is an IO::Scalar, that means IO::Scalar::PRINT will be
+invoked, and that method happens to delegate to the \f(CW\*(C`print()\*(C'\fR method
+of the same class. So the \fIreal\fR work is ultimately done by
+\&\fIIO::Scalar::print()\fR.
+.Sh "How methods work (on the master)"
+.IX Subsection "How methods work (on the master)"
+Consider using a method on the master:
+.PP
+.Vb 1
+\& $WT\->print("Hello, world!\en");
+.Ve
+.PP
+Since the master ($WT) is blessed into the class IO::WrapTie::Master,
+Perl first attempts to find a \f(CW\*(C`print()\*(C'\fR method there. Failing that,
+Perl next attempts to find a \f(CW\*(C`print()\*(C'\fR method in the superclass,
+IO::Handle. It just so happens that there \fIis\fR such a method;
+that method merely invokes the \f(CW\*(C`print\*(C'\fR i/o operator on the self object...
+and for that, see above!
+.PP
+But let's suppose we're dealing with a method which \fIisn't\fR part
+of IO::Handle... for example:
+.PP
+.Vb 1
+\& my $sref = $WT\->sref;
+.Ve
+.PP
+In this case, the intuitive behavior is to have the master delegate the
+method invocation to the slave (now do you see where the designations
+come from?). This is indeed what happens: IO::WrapTie::Master contains
+an \s-1AUTOLOAD\s0 method which performs the delegation.
+.PP
+So: when \f(CW\*(C`sref()\*(C'\fR can't be found in IO::Handle, the \s-1AUTOLOAD\s0 method
+of IO::WrapTie::Master is invoked, and the standard behavior of
+delegating the method to the underlying slave (here, an IO::Scalar)
+is done.
+.PP
+Sometimes, to get this to work properly, you may need to create
+a subclass of IO::WrapTie::Master which is an effective master for
+\&\fIyour\fR class, and do the delegation there.
+.SH "NOTES"
+.IX Header "NOTES"
+\&\fBWhy not simply use the object's \s-1OO\s0 interface?\fR
+ Because that means forsaking the use of named operators
+like \fIprint()\fR, and you may need to pass the object to a subroutine
+which will attempt to use those operators:
+.PP
+.Vb 2
+\& $O = FooHandle\->new(&FOO_RDWR, 2);
+\& $O\->print("Hello, world\en"); ### OO syntax is okay, BUT....
+.Ve
+.PP
+.Vb 2
+\& sub nope { print $_[0] "Nope!\en" }
+\& X nope($O); ### ERROR!!! (not a glob ref)
+.Ve
+.PP
+\&\fBWhy not simply use \f(BItie()\fB?\fR
+ Because (1) you have to use \fItied()\fR to invoke methods in the
+object's public interface (yuck), and (2) you may need to pass
+the tied symbol to another subroutine which will attempt to treat
+it in an OO\-way... and that will break it:
+.PP
+.Vb 2
+\& tie *T, 'FooHandle', &FOO_RDWR, 2;
+\& print T "Hello, world\en"; ### Operator is okay, BUT...
+.Ve
+.PP
+.Vb 1
+\& tied(*T)\->other_stuff; ### yuck! AND...
+.Ve
+.PP
+.Vb 2
+\& sub nope { shift\->print("Nope!\en") }
+\& X nope(\e*T); ### ERROR!!! (method "print" on unblessed ref)
+.Ve
+.PP
+\&\fBWhy a master and slave?
+ Why not simply write FooHandle to inherit from IO::Handle?\fR
+ I tried this, with an implementation similar to that of IO::Socket.
+The problem is that \fIthe whole point is to use this with objects
+that don't have an underlying file/socket descriptor.\fR.
+Subclassing IO::Handle will work fine for the \s-1OO\s0 stuff, and fine with
+named operators \fIif\fR you \fItie()\fR... but if you just attempt to say:
+.PP
+.Vb 2
+\& $IO = FooHandle\->new(&FOO_RDWR, 2);
+\& print $IO "Hello!\en";
+.Ve
+.PP
+you get a warning from Perl like:
+.PP
+.Vb 1
+\& Filehandle GEN001 never opened
+.Ve
+.PP
+because it's trying to do system-level i/o on an (unopened) file
+descriptor. To avoid this, you apparently have to \fItie()\fR the handle...
+which brings us right back to where we started! At least the
+IO::WrapTie mixin lets us say:
+.PP
+.Vb 2
+\& $IO = FooHandle\->new_tie(&FOO_RDWR, 2);
+\& print $IO "Hello!\en";
+.Ve
+.PP
+and so is not \fItoo\fR bad. \f(CW\*(C`:\-)\*(C'\fR
+.SH "WARNINGS"
+.IX Header "WARNINGS"
+Remember: this stuff is for doing FileHandle-like i/o on things
+\&\fIwithout underlying file descriptors\fR. If you have an underlying
+file descriptor, you're better off just inheriting from IO::Handle.
+.PP
+\&\fBBe aware that \f(BInew_tie()\fB always returns an instance of a
+kind of IO::WrapTie::Master...\fR it does \fBnot\fR return an instance
+of the i/o class you're tying to!
+.PP
+Invoking some methods on the master object causes \s-1AUTOLOAD\s0 to delegate
+them to the slave object... so it \fIlooks\fR like you're manipulating a
+\&\*(L"FooHandle\*(R" object directly, but you're not.
+.PP
+I have not explored all the ramifications of this use of \fItie()\fR.
+\&\fIHere there be dragons\fR.
+.SH "VERSION"
+.IX Header "VERSION"
+$Id: WrapTie.pm,v 1.2 2005/02/10 21:21:53 dfs Exp $
+.SH "AUTHOR"
+.IX Header "AUTHOR"
+.RE
+.IP "Primary Maintainer"
+.IX Item "Primary Maintainer"
+David F. Skoll (\fIdfs@roaringpenguin.com\fR).
+.RE
+.IP "Original Author"
+.IX Item "Original Author"
+Eryq (\fIeryq@zeegee.com\fR).
+President, ZeeGee Software Inc (\fIhttp://www.zeegee.com\fR).
projects / catagits/Gitalist.git / blobdiff