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work::mod_perl-2.0.10:UsersContributedoPerlrDoc.0.10::docs::api::APR::Table(3)

NAME
       APR::Table - Perl API for manipulating APR opaque string-content	tables

Synopsis
	 use APR::Table	();

	 $table	= APR::Table::make($pool, $nelts);
	 $table_copy = $table->copy($pool);

	 $table->clear();

	 $table->set($key => $val);
	 $table->unset($key);
	 $table->add($key, $val);

	 $val =	$table->get($key);
	 @val =	$table->get($key);

	 $table->merge($key => $val);

	 use APR::Const	-compile qw(:table);
	 $table_overlay	= $table_base->overlay($table_overlay, $pool);
	 $table_overlay->compress(APR::Const::OVERLAP_TABLES_MERGE);

	 $table_a->overlap($table_b, APR::Const::OVERLAP_TABLES_SET);

	 $table->do(sub	{print "key $_[0], value $_[1]\n"}, @valid_keys);

	 #Tied Interface
	 $value	= $table->{$key};
	 $table->{$key}	= $value;
	 print "got it"	if exists $table->{$key};

	 foreach my $key (keys %{$table}) {
	     print "$key = $table->{$key}\n";
	 }

Description
       "APR::Table" allows its users to	manipulate opaque string-content
       tables.

       On the C	level the "opaque string-content" means: you can put in
       '\0'-terminated strings and whatever you	put in your get	out.

       On the Perl level that means that we convert scalars into strings and
       store those strings. Any	special	information that was in	the Perl
       scalar is not stored. So	for example if a scalar	was marked as utf8,
       tainted or tied,	that information is not	stored.	When you get the data
       back as a Perl scalar you get only the string.

       The table's structure is	somewhat similar to the	Perl's hash structure,
       but allows multiple values for the same key.  An	access to the records
       stored in the table always requires a key.

       The key-value pairs are stored in the order they	are added.

       The keys	are case-insensitive.

       However as of the current implementation	if more	than value for the
       same key	is requested, the whole	table is lineary searched, which is
       very inefficient	unless the table is very small.

       "APR::Table" provides a TIE Interface.

       See apr/include/apr_tables.h in ASF's apr project for low level
       details.

API
       "APR::Table" provides the following functions and/or methods:

   "add"
       Add data	to a table, regardless of whether there	is another element
       with the	same key.

	 $table->add($key, $val);

       obj: $table ( "APR::Table object" )
	   The table to	add to.

       arg1: $key ( string )
	   The key to use.

       arg2: $val ( string )
	   The value to	add.

       ret: no return value
       since: 2.0.00

       When adding data, this function makes a copy of both the	key and	the
       value.

   "clear"
       Delete all of the elements from a table.

	 $table->clear();

       obj: $table ( "APR::Table object" )
	   The table to	clear.

       ret: no return value
       since: 2.0.00

   "compress"
       Eliminate redundant entries in a	table by either	overwriting or merging
       duplicates:

	 $table->compress($flags);

       obj: $table ( "APR::Table object" )
	   The table to	compress.

       arg1: $flags ("APR::Const constant")
	     APR::Const::OVERLAP_TABLES_MERGE -- to merge
	     APR::Const::OVERLAP_TABLES_SET   -- to overwrite

       ret: no return value
       since: 2.0.00

       Converts	multi-valued keys in $table into single-valued keys.  This
       function	takes duplicate	table entries and flattens them	into a single
       entry.  The flattening behavior is controlled by	the (mandatory)	$flags
       argument.

       When $flags == "APR::Const::OVERLAP_TABLES_SET",	each key will be set
       to the last value seen for that key.  For example, given	key/value
       pairs 'foo => bar' and 'foo => baz', 'foo' would	have a final value of
       'baz' after compression -- the 'bar' value would	be lost.

       When $flags == "APR::Const::OVERLAP_TABLES_MERGE", multiple values for
       the same	key are	flattened into a comma-separated list.	Given
       key/value pairs 'foo => bar' and	'foo =>	baz', 'foo' would have a final
       value of	'bar, baz' after compression.

       Access the constants via:

	 use APR::Const	-compile qw(:table);

       or an explicit:

	 use APR::Const	-compile qw(OVERLAP_TABLES_SET OVERLAP_TABLES_MERGE);

       "compress()" combined with "overlay()" does the same thing as
       "overlap()".

       Examples:

       o   "APR::Const::OVERLAP_TABLES_SET"

	   Start with table $table:

	     foo => "one"
	     foo => "two"
	     foo => "three"
	     bar => "beer"

	   which is done by:

	     use APR::Const    -compile	=> ':table';
	     my	$table = APR::Table::make($r->pool, TABLE_SIZE);

	     $table->set(bar =>	'beer');
	     $table->set(foo =>	'one');
	     $table->add(foo =>	'two');
	     $table->add(foo =>	'three');

	   Now compress	it using "APR::Const::OVERLAP_TABLES_SET":

	     $table->compress(APR::Const::OVERLAP_TABLES_SET);

	   Now table $table contains:

	     foo => "three"
	     bar => "beer"

	   The value three for the key foo, that was added last, took over the
	   other values.

       o   "APR::Const::OVERLAP_TABLES_MERGE"

	   Start with table $table:

	     foo => "one"
	     foo => "two"
	     foo => "three"
	     bar => "beer"

	   as in the previous example, now compress it using
	   "APR::Const::OVERLAP_TABLES_MERGE":

	     $table->compress(APR::Const::OVERLAP_TABLES_MERGE);

	   Now table $table contains:

	     foo => "one, two, three"
	     bar => "beer"

	   All the values for the same key were	merged into one	value.

   "copy"
       Create a	new table and copy another table into it.

	 $table_copy = $table->copy($p);

       obj: $table ( "APR::Table object" )
	   The table to	copy.

       arg1: $p	( "APR::Pool object" )
	   The pool to allocate	the new	table out of.

       ret: $table_copy	( "APR::Table object" )
	   A copy of the table passed in.

       since: 2.0.00

   "do"
       Iterate over all	the elements of	the table, invoking provided
       subroutine for each element.  The subroutine gets passed	as argument, a
       key-value pair.

	 $table->do(sub	{...}, @filter);

       obj: $table ( "APR::Table object" )
	   The table to	operate	on.

       arg1: $sub ( CODE ref/string )
	   A subroutine	reference or name to be	called on each item in the
	   table.  The subroutine can abort the	iteration by returning 0 and
	   should always return	1 otherwise.

       opt arg3: @filter ( ARRAY )
	   If passed, only keys	matching one of	the entries in f@filter	will
	   be processed.

       ret: no return value
       since: 2.0.00

       Examples:

       o   This	filter simply prints out the key/value pairs and counts	how
	   many	pairs did it see.

	     use constant TABLE_SIZE =>	20;
	     our $filter_count;
	     my	$table = APR::Table::make($r->pool, TABLE_SIZE);

	     # populate	the table with ascii data
	     for (1..TABLE_SIZE) {
		 $table->set(chr($_+97), $_);
	     }

	     $filter_count = 0;
	     $table->do("my_filter");
	     print "Counted $filter_count elements";

	     sub my_filter {
		 my ($key, $value) = @_;
		 warn "$key => $value\n";
		 $filter_count++;
		 return	1;
	     }

	   Notice that "my_filter" always returns 1, ensuring that "do()" will
	   pass	all the	key/value pairs.

       o   This	filter is similar to the one from the previous example,	but
	   this	time it	decides	to abort the filtering after seeing half of
	   the table, by returning 0 when this happens.

	     sub my_filter {
		 my ($key, $value) = @_;
		 $filter_count++;
		 return	$filter_count == int(TABLE_SIZE)/2 ? 0 : 1;
	     }

   "get"
       Get the value(s)	associated with	a given	key.  After this call, the
       data is still in	the table.

	 $val =	$table->get($key);
	 @val =	$table->get($key);

       obj: $table ( "APR::Table object" )
	   The table to	search for the key.

       arg1: $key ( string )
	   The key to search for.

       ret: $val or @val
	   In the scalar context the first matching value returned (the	oldest
	   in the table, if there is more than one value). If nothing matches
	   "undef" is returned.

	   In the list context the whole table is traversed and	all matching
	   values are returned.	An empty list is returned if nothing matches.

       since: 2.0.00

   "make"
       Make a new table.

	 $table	= APR::Table::make($p, $nelts);

       obj: $p ( "APR::Pool object" )
	   The pool to allocate	the pool out of.

       arg1: $nelts ( integer )
	   The number of elements in the initial table.	At least 1 or more. If
	   0 is	passed APR will	still allocate 1.

       ret: $table ( "APR::Table object" )
	   The new table.

       since: 2.0.00

       This table can only store text data.

   "merge"
       Add data	to a table by merging the value	with data that has already
       been stored using ", " as a separator:

	 $table->merge($key, $val);

       obj: $table ( "APR::Table object" )
	   The table to	search for the data.

       arg1: $key ( string )
	   The key to merge data for.

       arg2: $val ( string )
	   The data to add.

       ret: no return value
       since: 2.0.00

       If the key is not found,	then this function acts	like "add()".

       If there	is more	than one value for the same key, only the first	(the
       oldest) value gets merged.

       Examples:

       o   Start with a	pair:

	     merge => "1"

	   and merge "a" to the	value:

	     $table->set(  merge => '1');
	     $table->merge(merge => 'a');
	     $val = $table->get('merge');

	   Result:

	     $val == "1, a";

       o   Start with a	multivalued pair:

	     merge => "1"
	     merge => "2"

	   and merge "a" to the	first value;

	     $table->set(  merge => '1');
	     $table->add(  merge => '2');
	     $table->merge(merge => 'a');
	     @val = $table->get('merge');

	   Result:

	     $val[0] ==	"1, a";
	     $val[1] ==	"2";

	   Only	the first value	for the	same key is affected.

       o   Have	no entry and merge "a";

	     $table->merge(miss	=> 'a');
	     $val = $table->get('miss');

	   Result:

	     $val == "a";

   "overlap"
       For each	key/value pair in $table_b, add	the data to $table_a. The
       definition of $flags explains how $flags	define the overlapping method.

	 $table_a->overlap($table_b, $flags);

       obj: $table_a ( "APR::Table object" )
	   The table to	add the	data to.

       arg1: $table_b (	"APR::Table object" )
	   The table to	iterate	over, adding its data to table $table_a

       arg2: $flags ( integer )
	   How to add the table	to table $table_a.

	   When	$flags == "APR::Const::OVERLAP_TABLES_SET", if another element
	   already exists with the same	key, this will over-write the old
	   data.

	   When	$flags == "APR::Const::OVERLAP_TABLES_MERGE", the key/value
	   pair	from $table_b is added,	regardless of whether there is another
	   element with	the same key in	$table_a.

       ret: no return value
       since: 2.0.00

       Access the constants via:

	 use APR::Const	-compile qw(:table);

       or an explicit:

	 use APR::Const	-compile qw(OVERLAP_TABLES_SET OVERLAP_TABLES_MERGE);

       This function is	highly optimized, and uses less	memory and CPU cycles
       than a function that just loops through table $table_b calling other
       functions.

       Conceptually, "overlap()" does this:

	 apr_array_header_t *barr = apr_table_elts(b);
	 apr_table_entry_t *belt = (apr_table_entry_t *)barr-E<gt>elts;
	 int i;

	 for (i	= 0; i < barr->nelts; ++i) {
	     if	(flags & APR_OVERLAP_TABLES_MERGE) {
		 apr_table_mergen(a, belt[i].key, belt[i].val);
	     }
	     else {
		 apr_table_setn(a, belt[i].key,	belt[i].val);
	     }
	 }

       Except that it is more efficient	(less space and	cpu-time) especially
       when $table_b has many elements.

       Notice the assumptions on the keys and values in	$table_b -- they must
       be in an	ancestor of $table_a's pool.  In practice $table_b and
       $table_a	are usually from the same pool.

       Examples:

       o   "APR::Const::OVERLAP_TABLES_SET"

	   Start with table $base:

	     foo => "one"
	     foo => "two"
	     bar => "beer"

	   and table $add:

	     foo => "three"

	   which is done by:

	     use APR::Const    -compile	=> ':table';
	     my	$base =	APR::Table::make($r->pool, TABLE_SIZE);
	     my	$add  =	APR::Table::make($r->pool, TABLE_SIZE);

	     $base->set(bar => 'beer');
	     $base->set(foo => 'one');
	     $base->add(foo => 'two');

	     $add->set(foo => 'three');

	   Now overlap using "APR::Const::OVERLAP_TABLES_SET":

	     $base->overlap($add, APR::Const::OVERLAP_TABLES_SET);

	   Now table $add is unmodified	and table $base	contains:

	     foo => "three"
	     bar => "beer"

	   The value from table	"add" has overwritten all previous values for
	   the same key	both had (foo).	 This is the same as doing "overlay()"
	   followed by "compress()" with "APR::Const::OVERLAP_TABLES_SET".

       o   "APR::Const::OVERLAP_TABLES_MERGE"

	   Start with table $base:

	     foo => "one"
	     foo => "two"

	   and table $add:

	     foo => "three"
	     bar => "beer"

	   which is done by:

	     use APR::Const    -compile	=> ':table';
	     my	$base =	APR::Table::make($r->pool, TABLE_SIZE);
	     my	$add  =	APR::Table::make($r->pool, TABLE_SIZE);

	     $base->set(foo => 'one');
	     $base->add(foo => 'two');

	     $add->set(foo => 'three');
	     $add->set(bar => 'beer');

	   Now overlap using "APR::Const::OVERLAP_TABLES_MERGE":

	     $base->overlap($add, APR::Const::OVERLAP_TABLES_MERGE);

	   Now table $add is unmodified	and table $base	contains:

	     foo => "one, two, three"
	     bar => "beer"

	   Values from both tables for the same	key were merged	into one
	   value. This is the same as doing "overlay()"	followed by
	   "compress()"	with "APR::Const::OVERLAP_TABLES_MERGE".

   "overlay"
       Merge two tables	into one new table. The	resulting table	may have more
       than one	value for the same key.

	 $table	= $table_base->overlay($table_overlay, $p);

       obj: $table_base	( "APR::Table object" )
	   The table to	add at the end of the new table.

       arg1: $table_overlay ( "APR::Table object" )
	   The first table to put in the new table.

       arg2: $p	( "APR::Pool object" )
	   The pool to use for the new table.

       ret: $table ( "APR::Table object" )
	   A new table containing all of the data from the two passed in.

       since: 2.0.00

       Examples:

       o   Start with table $base:

	     foo => "one"
	     foo => "two"
	     bar => "beer"

	   and table $add:

	     foo => "three"

	   which is done by:

	     use APR::Const    -compile	=> ':table';
	     my	$base =	APR::Table::make($r->pool, TABLE_SIZE);
	     my	$add  =	APR::Table::make($r->pool, TABLE_SIZE);

	     $base->set(bar => 'beer');
	     $base->set(foo => 'one');
	     $base->add(foo => 'two');

	     $add->set(foo => 'three');

	   Now overlay using "APR::Const::OVERLAP_TABLES_SET":

	     my	$overlay = $base->overlay($add,	APR::Const::OVERLAP_TABLES_SET);

	   That	resulted in a new table	$overlay (tables "add" and $base are
	   unmodified) which contains:

	     foo => "one"
	     foo => "two"
	     foo => "three"
	     bar => "beer"

   "set"
       Add a key/value pair to a table,	if another element already exists with
       the same	key, this will over-write the old data.

	 $table->set($key, $val);

       obj: $table ( "APR::Table object" )
	   The table to	add the	data to.

       arg1: $key ( string )
	   The key to use.

       arg2: $val ( string )
	   The value to	add.

       ret: no return value
       since: 2.0.00

       When adding data, this function makes a copy of both the	key and	the
       value.

   "unset"
       Remove data from	the table.

	 $table->unset($key);

       obj: $table ( "APR::Table object" )
	   The table to	remove data from.

       arg1: $key ( string )
	   The key of the data being removed.

       ret: no return value
       since: 2.0.00

TIE Interface
       "APR::Table" also implements a tied interface, so you can work with the
       $table object as	a hash reference.

       The following tied-hash function	are supported: "FETCH",	"STORE",
       "DELETE", "CLEAR", "EXISTS", "FIRSTKEY",	"NEXTKEY" and "DESTROY".

       Note regarding the use of "values()". "APR::Table" can hold more	than
       one key-value pair sharing the same key,	so when	using a	table through
       the tied	interface, the first entry found with the right	key will be
       used, completely	disregarding possible other entries with the same key.
       With Perl 5.8.0 and higher "values()" will correctly list values	the
       corresponding to	the list generated by "keys()".	That doesn't work with
       Perl 5.6. Therefore to portably iterate over the	key-value pairs, use
       "each()"	(which fully supports multivalued keys), or "APR::Table::do".

   "EXISTS"
	 $ret =	$table->EXISTS($key);

       obj: $table ( "APR::Table object" )
       arg1: $key ( string )
       ret: $ret ( integer )
	   true	or false

       since: 2.0.00

   "CLEAR"
	 $table->CLEAR();

       obj: $table ( "APR::Table object" )
       ret: no return value
       since: 2.0.00

   "STORE"
	 $table->STORE($key, $val);

       obj: $table ( "APR::Table object" )
       arg1: $key ( string )
       arg2: $val ( string )
       ret: no return value
       since: 2.0.00

   "DELETE"
	 $table->DELETE($key);

       obj: $table ( "APR::Table object" )
       arg1: $key ( string )
       ret: no return value
       since: 2.0.00

   "FETCH"
	 $ret =	$table->FETCH($key);

       obj: $table ( "APR::Table object" )
       arg1: $key ( string )
       ret: $ret ( string )
       since: 2.0.00

       When iterating through the table's entries with "each()", "FETCH" will
       return the current value	of a multivalued key.  For example:

	 $table->add("a" => 1);
	 $table->add("b" => 2);
	 $table->add("a" => 3);

	 ($k, $v) = each %$table; # (a,	1)
	 print $table->{a};	  # prints 1

	 ($k, $v) = each %$table; # (b,	2)
	 print $table->{a};	  # prints 1

	 ($k, $v) = each %$table; # (a,	3)
	 print $table->{a};	  # prints 3 !!!

	 ($k, $v) = each %$table; # (undef, undef)
	 print $table->{a};	  # prints 1

See Also
       mod_perl	2.0 documentation.

Copyright
       mod_perl	2.0 and	its core modules are copyrighted under The Apache
       Software	License, Version 2.0.

Authors
       The mod_perl development	team and numerous contributors.

perl v5.24.1		       work::mod_perl-2.0.10::docs::api::APR::Table(3)

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