MM(3) User Contributed Perl Documentation MM(3)NAMEIPC::MM - Perl interface to Ralf Engelschall's mm library
SYNOPSIS
use IPC::MM;
$MMSIZE = 65536;
$MMFILE = 'mm_file';
$mm = mm_create($MMSIZE, $MM_FILE);
$scalar = mm_make_scalar($mm);
tie $tied_scalar, 'IPC::MM::Scalar', $scalar;
$tied_scalar = 'hello';
$btree = mm_make_btree_table($mm);
tie %tied_hash, 'IPC::MM::BTree', $btree;
$tied_hash{key} = 'val';
$hash = mm_make_hash($mm);
tie %tied_hash, 'IPC::MM::Hash', $hash;
$tied_hash{key} = 'val';
$num = mm_maxsize();
$num = mm_available($mm);
$errstr = mm_error();
mm_display_info($mm);
mm_destroy($mm);
DESCRIPTIONIPC::MM provides an interface to Ralf Engelschall's mm library, allow-
ing memory to be shared between multiple processes in a relatively con-
venient way.
IPC::MM provides methods to create and destoy shared memory segments
and to access data structures within those shared memory segments, as
well as miscellaneous methods. Additionally, it provides a tied inter-
face for scalars and hashes.
METHODS
$mm = mm_create($size, $file)
This method creates a shared memory segment. It corresponds to the
function in mm of the same name.
$size is the size of the shared memory segment, in bytes. A size of
0 means to allocate the maximum allowed size which is platform
dependent.
$file is a filesystem path to a file which may be used as a lock
file for synchronizing access.
$rc = mm_permission($mm, $mode, $owner, $group)
This method sets the filesystem mode, owner, and group for the
shared memory segment mm. It will only do anything when the under-
lying shared memory segment is based on files. It corresponds to
the function in mm of the same name.
$mm is the shared memory segment returned by mm_create.
$mode, $owner, and $group are passed directly to chown and chmod.
mm_destroy($mm)
This method destroys a shared memory segment created by mm_create.
$mm is the shared memory segment returned by mm_create.
$scalar = mm_make_scalar($mm)
mm_free_scalar($scalar)
$val = mm_scalar_get($scalar)
$rc = mm_scalar_set($scalar, $val)
This family of methods provides a data structure for use by scalar
variables.
mm_make_scalar allocates the data structure used by the scalar.
mm_free_scalar frees a data structure created by mm_make_scalar.
mm_scalar_get returns the contents of the scalar, $scalar.
mm_scalar_set sets the contents of the scalar, $scalar, to $val.
$val is simply a Perl scalar value, meaning that it can be a
string, a number, a reference, et al.
It is possible for mm_scalar_set to fail if there is not enough
shared memory.
It is possible to make the scalar a tied variable, like so:
tie $tied_scalar, 'IPC::MM::Scalar', $scalar;
$btree = mm_make_btree_table($mm)
mm_clear_btree_table($btree)
mm_free_btree_table($btree)
$val = mm_btree_table_get($btree, $key)
$rc = mm_btree_table_insert($btree, $key, $val)
$oldval = mm_btree_table_delete($btree, $key)
$rc = mm_btree_table_exists($btree, $key)
$key = mm_btree_table_first_key($btree)
$key = mm_btree_table_next_key($btree, $key)
This family of methods provides a btree data structure for use by
hashes.
mm_make_btree_table allocates the data structure.
mm_clear_btree_table clears the data structure, making it empty.
mm_free_btree_table frees the data structure.
mm_btree_table_get returns the value associated with $key.
mm_btree_table_insert inserts a new entry into the btree, with $key
equal to $val.
mm_btree_table_delete deletes the entry in the btree identified by
$key.
mm_btree_table_exists tests for the existence of an entry in the
btree identified by $key.
mm_btree_table_first_key returns the first key in the btree.
mm_btree_table_next_key returns the next key after $key in the
btree.
It is possible to tie a btree to a hash, like so:
tie %tied_hash, 'IPC::MM::BTree', $btree;
One interesting characteristic of the btree is that it is pre-
sorted, so keys %tied_hash will return a sorted list of items.
$hash = mm_make_hash($mm)
mm_hash_clear($hash)
mm_free_hash($hash)
$val = mm_hash_get($hash, $key)
$rc = mm_hash_insert($hash, $key, $val)
$oldval = mm_hash_delete($hash, $key)
$rc = mm_hash_exists($hash, $key)
$key = mm_hash_first_key($hash)
$key = mm_hash_next_key($hash, $key)
This family of methods implements a shared memory hash list. These
hash lists are not presorted like btrees, but they can be faster
than btrees (especially unbalanced btrees).
mm_make_hash allocates the data structure.
mm_clear_hash clears the data structure, making it empty.
mm_free_hash frees the data structure.
mm_hash_get returns the value associated with $key.
mm_hash_insert inserts a new entry into the hash, with $key equal
to $val.
mm_hash_delete deletes the entry in the hash identified by $key.
mm_hash_exists tests for the existence of an entry in the hash
identified by $key.
mm_hash_first_key returns the first key in the hash.
mm_hash_next_key returns the next key after $key in the hash.
It is possible to tie a shared-memory hash to a perl hash, like so:
tie %tied_hash, 'IPC::MM::Hash', $hash;
$rc = mm_lock($mm, $mode)
This method locks the shared memory pool $mm for the current
process in order to perform either shared/read-only (mode
MM_LOCK_RD) or exclusive/read-write (mode MM_LOCK_RW) operations.
$rc = mm_unlock($mm)
This method unlocks the shared memory pool $mm.
$num = mm_maxsize
This method returns the maximum allowable size for a shared memory
segment. It corresponds to the function of the same name in the mm
library.
$num = mm_available($mm)
This method returns the number of free bytes left in a shared mem-
ory segment. It corresponds to the function of the same name in
the mm library.
$mm is a shared memory segment created by mm_create.
$errstr = mm_error
This method returns an error string, if any. It corresponds to the
function of the same name in mm.
mm_display_info($mm)
This method displays some miscellaneous information about a shared
memory segment. It corresponds to the function of the same name in
mm.
BUGS
No effort is made to balance the btree.
AUTHOR
Copyright (c) 1999, Arthur Choung <arthur@etoys.com>. All rights
reserved.
This module is free software; you may redistribute it and/or modify it
under the same terms as Perl itself.
SEE ALSO
mm, IPC::Shareable, perl.
perl(1).
perl v5.8.8 2000-08-11 MM(3)
