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APR::Table - Perl API for for manipulating opaque string-content table | ||||
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use APR::Table (); $table = make($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 => $val); overlap($table_a, $table_b, $flags); $new_table = overlay($table_base, $table_overlay, $pool); $table->do(sub {print "key $_[0], value $_[1]\n"}, @valid_keys); #Tied Interface $value = $table->{$key}; $table->{$key} = $value; $table->{$key} = $value; exists $table->{$key}; foreach my $key (keys %{$table}) { print "$key = $table->{$key}\n"; }
APR::Table
allows its users to manipulate opaque string-content
tables.
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.
add
Add data to a table, regardless of whether there is another element with the same key.
$t->add($key, $val);
$t
(APR::Table
)
The table to add to.
$key
(string)
The key to use.
$val
(string)
The value to add.
When adding data, this function makes a copy of both the key and the value.
clear
Delete all of the elements from a table.
$t->clear();
$t
(APR::Table
)
The table to clear.
compress
Eliminate redundant entries in a table by either overwriting or merging duplicates:
$t->compress($flags);
$t
(APR::Table
)
The table to compress.
$flags
(integer)
APR::OVERLAP_TABLES_MERGE -- to merge APR::OVERLAP_TABLES_SET -- to overwrite
Converts multi-valued keys in $table
to 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::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::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.
copy
Create a new table and copy another table into it.
$ret = $t->copy($p);
$t
(APR::Table
)
The table to copy.
$p
(APR::Pool
)
The pool to allocate the new table out of.
$ret
(APR::Table
)
A copy of the table passed in.
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);
$p
(APR::Table
)
The table to operate on.
$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.
@filter
(ARRAY)
If passed, only keys matching one of the entries in the @filter
will be processed.
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);
$t
(APR::Table
)
The table to search for the key.
$key
(string)
The key to search for.
$val
or @val
In the scalar context the first matching value returned. (The oldest in the table, if there is more than one value.)
In the list context the whole table is traversed and all matching
values are returned. If nothing matches undef
is returned.
make
Make a new table.
$ret = make($p, $nelts);
$p
(APR::Pool
)
The pool to allocate the pool out of.
$nelts
(integer)
The number of elements in the initial table.
$ret
(APR::Table
)
The new table.
Note: This table can only store text data.
merge
Add data to a table by merging the value with data that has already been stored:
$t->merge($key, $val);
$t
(APR::Table
)
The table to search for the data.
$key
(string)
The key to merge data for.
$val
(string)
The data to add.
Note: if the key is not found, then this function acts like
add()
.
overlap
For each key/value pair in $t_b
, add the data to $t_a
. The
definition of $flags
explains how $flags
define the overlapping
method.
$t_a->overlap($t_b, $flags);
$t_a
(APR::Table
)
The table to add the data to.
$t_b
(APR::Table
)
The table to iterate over, adding its data to table $t_a
$flags
(integer)
How to add the table to table $t_a
.
When $flags
== APR::OVERLAP_TABLES_SET
, if another element
already exists with the same key, this will over-write the old data.
When $flags
== APR::OVERLAP_TABLES_MERGE
, the key/value pair
from $t_b
is added, regardless of whether there is another element
with the same key in $t_a
.
This function is highly optimized, and uses less memory and CPU cycles
than a function that just loops through table $t_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 E<lt> barr-E<gt>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 $t_b
has many elements.
Notice the assumptions on the keys and values in $t_b
-- they must
be in an ancestor of $t_a
's pool. In practice $t_b
and $t_a
are
usually from the same pool.
overlay
Merge two tables into one new table. The resulting table may have more than one value for the same key.
$t = $t_base->overlay($t_overlay, $p);
$t_base
(APR::Table
)
The table to add at the end of the new table.
$t_overlay
(APR::Table
)
The first table to put in the new table.
$p
(APR::Pool
)
The pool to use for the new table.
$t
(APR::Table
)
A new table containing all of the data from the two passed in.
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.
$t->set($key, $val);
$t
(APR::Table
)
The table to add the data to.
$key
(string)
The key to use.
$val
(string)
The value to add.
When adding data, this function makes a copy of both the key and the value.
unset
Remove data from the table.
$t->unset($key);
$t
(APR::Table
)
The table to remove data from.
$key
(string)
The key of the data being removed.
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.
remark: 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. The only
exception to this is if you iterate over the list with each, then
you can access all key-value pairs that share the same key.
STORE
$t->STORE($key, $value);
$t
(APR::Table
)
$key
(string)
$value
(string)
mod_perl 2.0 and its core modules are copyrighted under The Apache Software License, Version 1.1.
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