Integrate from mainperl.

p4raw-id: //depot/cfgperl@3337

7 files changed, 202 insertions, 3 deletions

diff --git a/pod/Makefile b/pod/Makefile
index f70c11b173..7db379ca90 100644
--- a/pod/Makefile
+++ b/pod/Makefile
@@ -43,6 +43,7 @@ POD = \
 	perlbot.pod	\
 	perlipc.pod	\
 	perlthrtut.pod	\
+	perldbmfilter.pod	\
 	perldebug.pod	\
 	perldiag.pod	\
 	perlsec.pod	\
@@ -100,6 +101,7 @@ MAN = \
 	perlbot.man	\
 	perlipc.man	\
 	perlthrtut.man	\
+	perldbmfilter.man	\
 	perldebug.man	\
 	perldiag.man	\
 	perlsec.man	\
@@ -157,6 +159,7 @@ HTML = \
 	perlbot.html	\
 	perlipc.html	\
 	perlthrtut.html	\
+	perldbmfilter.html	\
 	perldebug.html	\
 	perldiag.html	\
 	perlsec.html	\
@@ -214,6 +217,7 @@ TEX = \
 	perlbot.tex	\
 	perlipc.tex	\
 	perlthrtut.tex	\
+	perldbmfilter.tex	\
 	perldebug.tex	\
 	perldiag.tex	\
 	perlsec.tex	\
diff --git a/pod/buildtoc b/pod/buildtoc
index 8df5726771..62df02baba 100644
--- a/pod/buildtoc
+++ b/pod/buildtoc
@@ -10,7 +10,7 @@ sub output ($);
 	   perlsyn perlop perlre perlrun perlfunc perlvar perlsub
 	   perlmod perlmodlib perlmodinstall perlform perllocale 
 	   perlref perlreftut perldsc
-	   perllol perltoot perlobj perltie perlbot perlipc perldebug
+	   perllol perltoot perlobj perltie perlbot perlipc perldbmfilter perldebug
 	   perldiag perlsec perltrap perlport perlstyle perlpod perlbook
 	   perlembed perlapio perlxs perlxstut perlguts perlcall
 	   perlhist
diff --git a/pod/perl.pod b/pod/perl.pod
index 6605097689..8f688c72c4 100644
--- a/pod/perl.pod
+++ b/pod/perl.pod
@@ -50,6 +50,7 @@ of sections:
     perlbot		Perl OO tricks and examples
     perlipc		Perl interprocess communication
     perlthrtut		Perl threads tutorial
+    perldbmfilter	Perl DBM Filters
 
     perldebug		Perl debugging
     perldiag		Perl diagnostic messages
diff --git a/pod/perldbmfilter.pod b/pod/perldbmfilter.pod
new file mode 100644
index 0000000000..faed2d25d2
--- /dev/null
+++ b/pod/perldbmfilter.pod
@@ -0,0 +1,165 @@
+=head1 NAME
+
+perldbmfilter - Perl DBM Filters
+
+=head1 SYNOPSIS
+
+    $db = tie %hash, 'DBM', ...
+
+    $old_filter = $db->filter_store_key  ( sub { ... } ) ;
+    $old_filter = $db->filter_store_value( sub { ... } ) ;
+    $old_filter = $db->filter_fetch_key  ( sub { ... } ) ;
+    $old_filter = $db->filter_fetch_value( sub { ... } ) ;
+
+=head1 DESCRIPTION
+
+The four C<filter_*> methods shown above are available in all the DBM
+modules that ship with Perl, namely DB_File, GDBM_File, NDBM_File,
+ODBM_File and SDBM_File.
+
+Each of the methods work identically, and are used to install (or
+uninstall) a single DBM Filter. The only difference between them is the
+place that the filter is installed.
+
+To summarise:
+
+=over 5
+
+=item B<filter_store_key>
+
+If a filter has been installed with this method, it will be invoked
+every time you write a key to a DBM database.
+
+=item B<filter_store_value>
+
+If a filter has been installed with this method, it will be invoked
+every time you write a value to a DBM database.
+
+
+=item B<filter_fetch_key>
+
+If a filter has been installed with this method, it will be invoked
+every time you read a key from a DBM database.
+
+=item B<filter_fetch_value>
+
+If a filter has been installed with this method, it will be invoked
+every time you read a value from a DBM database.
+
+=back
+
+You can use any combination of the methods from none to all four.
+
+All filter methods return the existing filter, if present, or C<undef>
+in not.
+
+To delete a filter pass C<undef> to it.
+
+=head2 The Filter
+
+When each filter is called by Perl, a local copy of C<$_> will contain
+the key or value to be filtered. Filtering is achieved by modifying
+the contents of C<$_>. The return code from the filter is ignored.
+
+=head2 An Example -- the NULL termination problem.
+
+DBM Filters are useful for a class of problems where you I<always>
+want to make the same transformation to all keys, all values or both.
+
+For example, consider the following scenario. You have a DBM database
+that you need to share with a third-party C application. The C application
+assumes that I<all> keys and values are NULL terminated. Unfortunately
+when Perl writes to DBM databases it doesn't use NULL termination, so
+your Perl application will have to manage NULL termination itself. When
+you write to the database you will have to use something like this:
+
+    $hash{"$key\0"} = "$value\0" ;
+
+Similarly the NULL needs to be taken into account when you are considering
+the length of existing keys/values.
+
+It would be much better if you could ignore the NULL terminations issue
+in the main application code and have a mechanism that automatically
+added the terminating NULL to all keys and values whenever you write to
+the database and have them removed when you read from the database. As I'm
+sure you have already guessed, this is a problem that DBM Filters can
+fix very easily.
+
+    use strict ;
+    use SDBM_File ;
+    use Fcntl ;
+
+    my %hash ;
+    my $filename = "/tmp/filt" ;
+    unlink $filename ;
+
+    my $db = tie(%hash, 'SDBM_File', $filename, O_RDWR|O_CREAT, 0640)
+      or die "Cannot open $filename: $!\n" ;
+
+    # Install DBM Filters
+    $db->filter_fetch_key  ( sub { s/\0$//    } ) ;
+    $db->filter_store_key  ( sub { $_ .= "\0" } ) ;
+    $db->filter_fetch_value( sub { s/\0$//    } ) ;
+    $db->filter_store_value( sub { $_ .= "\0" } ) ;
+
+    $hash{"abc"} = "def" ;
+    my $a = $hash{"ABC"} ;
+    # ...
+    undef $db ;
+    untie %hash ;
+
+The code above uses SDBM_File, but it will work with any of the DBM
+modules.
+
+Hopefully the contents of each of the filters should be
+self-explanatory. Both "fetch" filters remove the terminating NULL,
+and both "store" filters add a terminating NULL.
+
+
+=head2 Another Example -- Key is a C int.
+
+Here is another real-life example. By default, whenever Perl writes to
+a DBM database it always writes the key and value as strings. So when
+you use this:
+
+    $hash{12345} = "soemthing" ;
+
+the key 12345 will get stored in the DBM database as the 5 byte string
+"12345". If you actually want the key to be stored in the DBM database
+as a C int, you will have to use C<pack> when writing, and C<unpack>
+when reading.
+
+Here is a DBM Filter that does it:
+
+    use strict ;
+    use DB_File ;
+    my %hash ;
+    my $filename = "/tmp/filt" ;
+    unlink $filename ;
+
+
+    my $db = tie %hash, 'DB_File', $filename, O_CREAT|O_RDWR, 0666, $DB_HASH 
+      or die "Cannot open $filename: $!\n" ;
+
+    $db->filter_fetch_key  ( sub { $_ = unpack("i", $_) } ) ;
+    $db->filter_store_key  ( sub { $_ = pack ("i", $_) } ) ;
+    $hash{123} = "def" ;
+    # ...
+    undef $db ;
+    untie %hash ;
+
+The code above uses DB_File, but again it will work with any of the
+DBM modules.
+
+This time only two filters have been used -- we only need to manipulate
+the contents of the key, so it wasn't necessary to install any value
+filters.
+
+=head1 SEE ALSO
+
+L<DB_File>, L<GDBM_File>, L<NDBM_File>, L<ODBM_File> and L<SDBM_File>.
+
+=head1 AUTHOR
+
+Paul Marquess
+
diff --git a/pod/perldelta.pod b/pod/perldelta.pod
index 8bf59abae9..ca6a6386b8 100644
--- a/pod/perldelta.pod
+++ b/pod/perldelta.pod
@@ -341,6 +341,11 @@ instead of
 
 	$fullname = File::Spec->catfile($dir1, $dir2, $file);
 
+=item Math::BigInt
+
+The logical operations C<E<lt>E<lt>>, C<E<gt>E<gt>>, C<&>, C<|>
+and C<~> are now supported on bigints.
+
 =item Math::Complex
 
 The accessor methods Re, Im, arg, abs, rho, and theta, can now also
@@ -386,6 +391,21 @@ pathname for FILENAME in scalar context. In list context it returns
 a two element list containing the fully qualified directory name and
 the filename.
 
+=item DBM Filters
+
+A new feature called "DBM Filters" has been added to all the
+DBM modules -- DB_File, GDBM_File, NDBM_File, ODBM_File and SDBM_File.
+DBM Filters add four new methods to each of the DBM modules 
+
+    filter_store_key
+    filter_store_value
+    filter_fetch_key
+    filter_fetch_value
+
+These can be used to filter the contents of keys/values before they are
+written to the database or just after they are read from the database.
+See L<perldbmfilter> for further information.
+
 =back
 
 =head2 Pragmata
diff --git a/pod/perlfunc.pod b/pod/perlfunc.pod
index c973d0c367..a65e3e3e46 100644
--- a/pod/perlfunc.pod
+++ b/pod/perlfunc.pod
@@ -546,7 +546,9 @@ number of characters removed from all its arguments.  It's often used to
 remove the newline from the end of an input record when you're worried
 that the final record may be missing its newline.  When in paragraph
 mode (C<$/ = "">), it removes all trailing newlines from the string.
-If VARIABLE is omitted, it chomps C<$_>.  Example:
+When in slurp mode (C<$/ = undef>) or fixed-length record mode (C<$/> is
+a reference to an integer or the like, see L<perlvar>) chomp() won't
+remove anything.  If VARIABLE is omitted, it chomps C<$_>.  Example:
 
     while (<>) {
 	chomp;	# avoid \n on last field
@@ -4611,6 +4613,11 @@ The following efficiently counts the number of set bits in a bit vector:
 
     $setbits = unpack("%32b*", $selectmask);
 
+The C<"p"> and C<"P"> formats should be used with care.  Since Perl
+has no way of checking whether the value passed to C<unpack()>
+corresponds to a valid memory location, passing a pointer value that's
+not known to be valid is likely to have disastrous consequences.
+
 See L</pack> for more examples.
 
 =item untie VARIABLE
diff --git a/pod/perltie.pod b/pod/perltie.pod
index 665265818d..581b4abd65 100644
--- a/pod/perltie.pod
+++ b/pod/perltie.pod
@@ -621,7 +621,9 @@ This is partially implemented now.
 
 A class implementing a tied filehandle should define the following
 methods: TIEHANDLE, at least one of PRINT, PRINTF, WRITE, READLINE, GETC,
-READ, and possibly CLOSE and DESTROY.
+READ, and possibly CLOSE and DESTROY.  The class can also provide: BINMODE, 
+OPEN, EOF, FILENO, SEEK, TELL - if the corresponding perl operators are
+used on the handle.
 
 It is especially useful when perl is embedded in some other program,
 where output to STDOUT and STDERR may have to be redirected in some