lib/charnames.t: Move initialization line

[perl5.git] / lib / PerlIO.pm

diff --git a/lib/PerlIO.pm b/lib/PerlIO.pm
index 24bc2b2..7658ce4 100644 (file)
--- a/lib/PerlIO.pm
+++ b/lib/PerlIO.pm
@@ -1,6 +1,6 @@
 package PerlIO;
 
 package PerlIO;
 

-our $VERSION = '1.02';
+our $VERSION = '1.10';

 
 # Map layer name to package that defines it
 our %alias;
 
 # Map layer name to package that defines it
 our %alias;


@@ -19,7 +19,7 @@ sub import
     {
      $layer = "${class}::$layer";
     }
     {
      $layer = "${class}::$layer";
     }

-   eval "require $layer";
+   eval { require $layer =~ s{::}{/}gr . '.pm' };

    warn $@ if $@;
   }
 }
    warn $@ if $@;
   }
 }


@@ -35,9 +35,10 @@ PerlIO - On demand loader for PerlIO layers and root of PerlIO::* name space
 
 =head1 SYNOPSIS
 
 
 =head1 SYNOPSIS
 

-  open($fh,"<:crlf", "my.txt"); # portably open a text file for reading
+  open($fh, "<:crlf", "my.txt"); # support platform-native and 
+                                 # CRLF text files

 
 

-  open($fh,"<","his.jpg");      # portably open a binary file for reading
+  open($fh, "<", "his.jpg"); # portably open a binary file for reading

   binmode($fh);
 
   Shell:
   binmode($fh);
 
   Shell:


@@ -61,38 +62,50 @@ The following layers are currently defined:
 
 =over 4
 
 
 =over 4
 

-=item unix
+=item :unix

 
 

-Low level layer which calls C<read>, C<write> and C<lseek> etc.
+Lowest level layer which provides basic PerlIO operations in terms of
+UNIX/POSIX numeric file descriptor calls
+(open(), read(), write(), lseek(), close()).

 
 

-=item stdio
+=item :stdio

 
 Layer which calls C<fread>, C<fwrite> and C<fseek>/C<ftell> etc.  Note
 that as this is "real" stdio it will ignore any layers beneath it and
 
 Layer which calls C<fread>, C<fwrite> and C<fseek>/C<ftell> etc.  Note
 that as this is "real" stdio it will ignore any layers beneath it and

-got straight to the operating system via the C library as usual.
+go straight to the operating system via the C library as usual.

 
 

-=item perlio
+=item :perlio

 
 

-This is a re-implementation of "stdio-like" buffering written as a
-PerlIO "layer".  As such it will call whatever layer is below it for
-its operations.
+A from scratch implementation of buffering for PerlIO. Provides fast
+access to the buffer for C<sv_gets> which implements perl's readline/E<lt>E<gt>
+and in general attempts to minimize data copying.

 
 

-=item crlf
+C<:perlio> will insert a C<:unix> layer below itself to do low level IO.

 
 

-A layer which does CRLF to "\n" translation distinguishing "text" and
-"binary" files in the manner of MS-DOS and similar operating systems.
-(It currently does I<not> mimic MS-DOS as far as treating of Control-Z
-as being an end-of-file marker.)
+=item :crlf

 
 

-=item utf8
+A layer that implements DOS/Windows like CRLF line endings.  On read
+converts pairs of CR,LF to a single "\n" newline character.  On write
+converts each "\n" to a CR,LF pair.  Note that this layer will silently
+refuse to be pushed on top of itself.

 
 

-Declares that the stream accepts perl's internal encoding of
+It currently does I<not> mimic MS-DOS as far as treating of Control-Z
+as being an end-of-file marker.
+
+Based on the C<:perlio> layer.
+
+=item :utf8
+
+Declares that the stream accepts perl's I<internal> encoding of

 characters.  (Which really is UTF-8 on ASCII machines, but is
 UTF-EBCDIC on EBCDIC machines.)  This allows any character perl can
 represent to be read from or written to the stream. The UTF-X encoding
 is chosen to render simple text parts (i.e.  non-accented letters,
 digits and common punctuation) human readable in the encoded file.
 
 characters.  (Which really is UTF-8 on ASCII machines, but is
 UTF-EBCDIC on EBCDIC machines.)  This allows any character perl can
 represent to be read from or written to the stream. The UTF-X encoding
 is chosen to render simple text parts (i.e.  non-accented letters,
 digits and common punctuation) human readable in the encoded file.
 

+(B<CAUTION>: This layer does not validate byte sequences.  For reading input,
+you should instead use C<:encoding(UTF-8)> instead of bare C<:utf8>.)
+

 Here is how to write your native data out using UTF-8 (or UTF-EBCDIC)
 and then read it back in.
 
 Here is how to write your native data out using UTF-8 (or UTF-EBCDIC)
 and then read it back in.
 


@@ -104,29 +117,36 @@ and then read it back in.
        $in = <F>;
        close(F);
 
        $in = <F>;
        close(F);
 

-=item bytes

 
 

-This is the inverse of C<:utf8> layer. It turns off the flag
+=item :bytes
+
+This is the inverse of the C<:utf8> layer. It turns off the flag

 on the layer below so that data read from it is considered to
 on the layer below so that data read from it is considered to

-be "octets" i.e. characters in range 0..255 only. Likewise
+be "octets" i.e. characters in the range 0..255 only. Likewise

 on output perl will warn if a "wide" character is written
 to a such a stream.
 
 on output perl will warn if a "wide" character is written
 to a such a stream.
 

-=item raw
+=item :raw

 
 The C<:raw> layer is I<defined> as being identical to calling
 
 The C<:raw> layer is I<defined> as being identical to calling

-C<binmode($fh)> - the stream is made suitable for passing binary
-data i.e. each byte is passed as-is. The stream will still be
-buffered. Unlike earlier versions of perl C<:raw> is I<not> just the
-inverse of C<:crlf> - other layers which would affect the binary nature of
-the stream are also removed or disabled.
+C<binmode($fh)> - the stream is made suitable for passing binary data,
+i.e. each byte is passed as-is. The stream will still be
+buffered.
+
+In Perl 5.6 and some books the C<:raw> layer (previously sometimes also
+referred to as a "discipline") is documented as the inverse of the
+C<:crlf> layer. That is no longer the case - other layers which would
+alter the binary nature of the stream are also disabled.  If you want UNIX
+line endings on a platform that normally does CRLF translation, but still
+want UTF-8 or encoding defaults, the appropriate thing to do is to add
+C<:perlio> to the PERLIO environment variable.

 
 The implementation of C<:raw> is as a pseudo-layer which when "pushed"
 pops itself and then any layers which do not declare themselves as suitable
 for binary data. (Undoing :utf8 and :crlf are implemented by clearing
 flags rather than popping layers but that is an implementation detail.)
 
 
 The implementation of C<:raw> is as a pseudo-layer which when "pushed"
 pops itself and then any layers which do not declare themselves as suitable
 for binary data. (Undoing :utf8 and :crlf are implemented by clearing
 flags rather than popping layers but that is an implementation detail.)
 

-As a consequence of the fact that C<:raw> normally pops layers
+As a consequence of the fact that C<:raw> normally pops layers,

 it usually only makes sense to have it as the only or first element in
 a layer specification.  When used as the first element it provides
 a known base on which to build e.g.
 it usually only makes sense to have it as the only or first element in
 a layer specification.  When used as the first element it provides
 a known base on which to build e.g.


@@ -135,22 +155,27 @@ a known base on which to build e.g.
 
 will construct a "binary" stream, but then enable UTF-8 translation.
 
 
 will construct a "binary" stream, but then enable UTF-8 translation.
 

-=item pop
+=item :pop

 
 

-A pseudo layer that removes the top-most layer. Gives perl code
-a way to manipulate the layer stack. Should be considered
-as experimental. Note that C<:pop> only works on real layers
-and will not undo the effects of pseudo layers like C<:utf8>.
-An example of a possible use might be:
+A pseudo layer that removes the top-most layer. Gives perl code a
+way to manipulate the layer stack.  Note that C<:pop> only works on
+real layers and will not undo the effects of pseudo layers like
+C<:utf8>.  An example of a possible use might be:

 
     open($fh,...)
     ...
     binmode($fh,":encoding(...)");  # next chunk is encoded
     ...
 
     open($fh,...)
     ...
     binmode($fh,":encoding(...)");  # next chunk is encoded
     ...

-    binmode($fh,":pop");            # back to un-encocded
+    binmode($fh,":pop");            # back to un-encoded

 
 A more elegant (and safer) interface is needed.
 
 
 A more elegant (and safer) interface is needed.
 

+=item :win32
+
+On Win32 platforms this I<experimental> layer uses the native "handle" IO
+rather than the unix-like numeric file descriptor layer. Known to be
+buggy as of perl 5.8.2.
+

 =back
 
 =head2 Custom Layers
 =back
 
 =head2 Custom Layers


@@ -164,11 +189,25 @@ in Perl using the latter) come with the Perl distribution.
 =item :encoding
 
 Use C<:encoding(ENCODING)> either in open() or binmode() to install
 =item :encoding
 
 Use C<:encoding(ENCODING)> either in open() or binmode() to install

-a layer that does transparently character set and encoding transformations,
+a layer that transparently does character set and encoding transformations,

 for example from Shift-JIS to Unicode.  Note that under C<stdio>
 an C<:encoding> also enables C<:utf8>.  See L<PerlIO::encoding>
 for more information.
 
 for example from Shift-JIS to Unicode.  Note that under C<stdio>
 an C<:encoding> also enables C<:utf8>.  See L<PerlIO::encoding>
 for more information.
 

+=item :mmap
+
+A layer which implements "reading" of files by using C<mmap()> to
+make a (whole) file appear in the process's address space, and then
+using that as PerlIO's "buffer". This I<may> be faster in certain
+circumstances for large files, and may result in less physical memory
+use when multiple processes are reading the same file.
+
+Files which are not C<mmap()>-able revert to behaving like the C<:perlio>
+layer. Writes also behave like the C<:perlio> layer, as C<mmap()> for write
+needs extra house-keeping (to extend the file) which negates any advantage.
+
+The C<:mmap> layer will not exist if the platform does not support C<mmap()>.
+

 =item :via
 
 Use C<:via(MODULE)> either in open() or binmode() to install a layer
 =item :via
 
 Use C<:via(MODULE)> either in open() or binmode() to install a layer


@@ -185,10 +224,10 @@ To get a binary stream an alternate method is to use:
     open($fh,"whatever")
     binmode($fh);
 
     open($fh,"whatever")
     binmode($fh);
 

-this has advantage of being backward compatible with how such things have
+this has the advantage of being backward compatible with how such things have

 had to be coded on some platforms for years.
 
 had to be coded on some platforms for years.
 

-To get an un-buffered stream specify an unbuffered layer (e.g. C<:unix>)
+To get an unbuffered stream specify an unbuffered layer (e.g. C<:unix>)

 in the open call:
 
     open($fh,"<:unix",$path)
 in the open call:
 
     open($fh,"<:unix",$path)


@@ -203,8 +242,8 @@ translation for text files then the default layers are :
 (The low level "unix" layer may be replaced by a platform specific low
 level layer.)
 
 (The low level "unix" layer may be replaced by a platform specific low
 level layer.)
 

-Otherwise if C<Configure> found out how to do "fast" IO using system's
-stdio, then the default layers are :
+Otherwise if C<Configure> found out how to do "fast" IO using the system's
+stdio, then the default layers are:

 
   unix stdio
 
 
   unix stdio
 


@@ -224,32 +263,33 @@ This can be used to see the effect of/bugs in the various layers e.g.
   PERLIO=stdio  ./perl harness
   PERLIO=perlio ./perl harness
 
   PERLIO=stdio  ./perl harness
   PERLIO=perlio ./perl harness
 

-For the various value of PERLIO see L<perlrun/PERLIO>.
+For the various values of PERLIO see L<perlrun/PERLIO>.

 
 

-=head2 Querying the layers of filehandle
+=head2 Querying the layers of filehandles

 
 The following returns the B<names> of the PerlIO layers on a filehandle.
 
    my @layers = PerlIO::get_layers($fh); # Or FH, *FH, "FH".
 
 The layers are returned in the order an open() or binmode() call would
 
 The following returns the B<names> of the PerlIO layers on a filehandle.
 
    my @layers = PerlIO::get_layers($fh); # Or FH, *FH, "FH".
 
 The layers are returned in the order an open() or binmode() call would

-use them.  Note that the stack begins (normally) from C<stdio> or from
-C<perlio>.  Under C<stdio> the platform specific low-level I/O (like
-C<unix>) is not part of the stack, but under C<perlio> (and the
-experimental C<mmap>) it is.
+use them.  Note that the "default stack" depends on the operating
+system and on the Perl version, and both the compile-time and
+runtime configurations of Perl.

 
 The following table summarizes the default layers on UNIX-like and
 
 The following table summarizes the default layers on UNIX-like and

-DOS-like platforms and depending on the setting of the C<$ENV{PERLIO}>:
+DOS-like platforms and depending on the setting of C<$ENV{PERLIO}>:
+
+ PERLIO     UNIX-like                   DOS-like
+ ------     ---------                   --------
+ unset / "" unix perlio / stdio [1]     unix crlf
+ stdio      unix perlio / stdio [1]     stdio
+ perlio     unix perlio                 unix perlio

 
 

- PERLIO     UNIX-like       DOS-like
- 
- none or "" stdio           unix crlf
- stdio      stdio           stdio
- perlio     unix perlio     unix perlio
- mmap       unix mmap       unix mmap
+ # [1] "stdio" if Configure found out how to do "fast stdio" (depends
+ # on the stdio implementation) and in Perl 5.8, otherwise "unix perlio"

 
 

-By default the layers from the input side of the filehandle is
-returned, to get the output side use the optional C<output> argument:
+By default the layers from the input side of the filehandle are
+returned; to get the output side, use the optional C<output> argument:

 
    my @layers = PerlIO::get_layers($fh, output => 1);
 
 
    my @layers = PerlIO::get_layers($fh, output => 1);
 


@@ -265,10 +305,10 @@ You are supposed to use open() and binmode() to manipulate the stack.
 
 B<Implementation details follow, please close your eyes.>
 
 
 B<Implementation details follow, please close your eyes.>
 

-The arguments to layers are by default returned in parenthesis after
+The arguments to layers are by default returned in parentheses after

 the name of the layer, and certain layers (like C<utf8>) are not real
 the name of the layer, and certain layers (like C<utf8>) are not real

-layers but instead flags on real layers: to get all of these returned
-separately use the optional C<separate> argument:
+layers but instead flags on real layers; to get all of these returned
+separately, use the optional C<details> argument:

 
    my @layer_and_args_and_flags = PerlIO::get_layers($fh, details => 1);
 
 
    my @layer_and_args_and_flags = PerlIO::get_layers($fh, details => 1);
 


@@ -289,4 +329,3 @@ L<perlfunc/"binmode">, L<perlfunc/"open">, L<perlunicode>, L<perliol>,
 L<Encode>
 
 =cut
 L<Encode>
 
 =cut

-