APR::Table - Perl API for manipulating APR opaque string-content tables
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";
}
"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.
"APR::Table" provides the following functions and/or methods:
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.
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
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:
- •
- "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.
- •
- "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.
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
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:
- •
- 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";
$filter_count++;
return 1;
}
Notice that "my_filter" always returns 1, ensuring that
"do()" will pass all the key/value pairs.
- •
- This filter is similar to the one from the previous
example, but this time it decides to abort the filtering after seeing half
of the table, by returning 0 when this happens.
sub my_filter {
my ($key, $value) = @_;
$filter_count++;
return $filter_count == int(TABLE_SIZE)/2 ? 0 : 1;
}
Get 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 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.
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:
- •
- 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";
- •
- 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.
- •
- Have no entry and merge "a";
$table->merge(miss => 'a');
$val = $table->get('miss');
Result:
$val == "a";
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:
- •
- "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".
- •
- "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".
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:
- •
- 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"
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.
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
"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".
$ret = $table->EXISTS($key);
- obj: $table ( "APR::Table object" )
- arg1: $key ( string )
- ret: $ret ( integer )
- true or false
- since: 2.0.00
$table->CLEAR();
- obj: $table ( "APR::Table object" )
- ret: no return value
- since: 2.0.00
$table->STORE($key, $val);
- obj: $table ( "APR::Table object" )
- arg1: $key ( string )
- arg2: $val ( string )
- ret: no return value
- since: 2.0.00
$table->DELETE($key);
- obj: $table ( "APR::Table object" )
- arg1: $key ( string )
- ret: no return value
- since: 2.0.00
$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
mod_perl 2.0 documentation.
mod_perl 2.0 and its core modules are copyrighted under The Apache Software
License, Version 2.0.
The mod_perl development team and numerous contributors.