Category: Win32 Stuff
Author/Contact Info Chad Johnston
Description: Memory information for Win32. Total and available physical, page, and virtual memory.
This is my first ever module, so any constructive criticism will be eagerly welcomed!
Update (1 Sept 00): Completely reworked the after tye's comments. This module is very different from the original.

This module has been superceded by Win32::SystemInfo.
#  Copyright (c) 2000 by Chad Johnston.  All rights reserved.

package Win32::MemoryInfo;

use Win32::API;
use strict;
use vars qw($VERSION);

$VERSION = '0.02';

sub MemoryStatus (\%;$) {
   my $return = shift;    #hash to return
   my $ret_type = shift;  #what format does the user want?
   my %fmt_types = 
   ( B => 1, KB => 1024, MB => 1024*1024, GB => 1024*1024*1024);
   my @params = qw(MemLoad TotalPhys AvailPhys TotalPage
                   AvailPage TotalVirtual AvailVirtual);
   my %results;          #results of fn call
   my $MemFormat;        #divisor for format
   my $dwMSLength;       #validator from fn call

   $MemFormat = 
   ($ret_type =~ /^[BKMG]B?$/) ? $fmt_types{$ret_type} : $fmt_types{B}

   my $GlobalMemoryStatus ||= 
   new Win32::API("kernel32", "GlobalMemoryStatus", ["P"], "V") or ret
   my $MEMORYSTATUS = pack "L8",(0, 0, 0, 0, 0, 0, 0, 0);

   ($dwMSLength, @results{@params})  =
   unpack "L8", $MEMORYSTATUS;
   return undef if ($dwMSLength == 0);

   if (keys(%$return) == 0) {
   foreach (@params) {
    $return->{$_} = ($_ eq "MemLoad") ? $results{$_} : $results{$_}/$M
   else {
    foreach (@params){
     $return->{$_} = $results{$_}/$MemFormat unless (!defined($return-


=head1 NAME

Win32::MemoryInfo - Memory information on Win32 systems


    use Win32::MemoryInfo;

    my %mHash;
    if (Win32::MemoryInfo::MemoryStatus(%mHash))
     ...process results...
    To get specific values: 
    my %mHash = (TotalPhys => 0, AvailPhys => 0);
    if (Win32::MemoryInfo::MemoryStatus(%mHash))
     ...mHash contains only TotalPhys and AvailPhys values...
    Change the default return value:


With this module you can get total/free memory on Win32 systems,
including installed RAM (physical memory) and page file. 

The current version of Win32::MemoryInfo is available at:

  [nowhere yet]


=over 4

Module provides one function:

=item MemoryStatus


   %mHash                      - The hash that will receive the result
                                 Certain values can be set prior to th
                                 call to retrieve a subset. (See below
   $format                     - Optional parameter. Used to set the o
                                 of magnitude of the results. (See bel

   Determines the current memory status of a Win32 machine. Populates
   %mHash with the results. Function returns undef on failure.
   Values returned through the hash:
   MemLoad                     - Windows NT 3.1 to 4.0: The percentage
+ of
                                 approximately the last 1000 pages of 
                                 memory that is in use.
                               - Windows 2000: The approximate percent
+age of
                                 total physical memory that is in use.
   TotalPhys                   - Total amount of physical memory (RAM)
   AvailPhys                   - Available physical memory (RAM).
   TotalPage                   - Allocated size of page (swap) file.
   AvailPage                   - Available page file memory.
   TotalVirtual                - Total physical + maximum page file.
   AvailableVirtual            - Total amount of available memory.
   Values returned through the hash can also be specified by setting
   them before the function is called. 
       my %mHash = (TotalPhys => 0);
   Will return only the total physical memory.
   MemoryStatus return values in bytes by default. This can be changed
+ with
   the $format parameter. Valid values for $format are:
       B        -  Bytes (default)
       KB       -  Kilobytes
       MB       -  Megabytes
       GB       -  Gigabytes


No functions are exported. 


This module can be used by simply placing it in your /Win32 directory
somewhere in @INC.

Use pod2html to build a html version of this POD.

This module requires
Win32::API module by Aldo Calpini

=head1 CAVEATS

The information returned by the MemoryStatus function is volatile. 
There is no guarantee that two sequential calls to this function
will return the same information. 

On computers with more than 4 GB of memory, the MemoryStatus function
can return incorrect information. Windows 2000 reports a value of -1
to indicate an overflow. Earlier versions of Windows NT report a value
that is the real amount of memory, modulo 4 GB. 

On Intel x86 computers with more than 2 GB and less than 4 GB of memor
the MemoryStatus function will always return 2 GB for TotalPhys. 
Similarly, if the total available memory is between 2 and 4 GB, AvailP
will be rounded down to 2 GB.  

This module has been created and tested in a WinNT 4.0 environment on 
port of Perl 5.6. It has B<not> been tested on Win95/98 or Windows 200
+0 yet.

=head1 CHANGES

 0.02 - Removed SetMemResultType and GetMemResultType
      - Changed return type and parameters.
      - Lots of other changes
 0.01 - Initial Release

=head1 BUGS

Please report.

=head1 VERSION

This man page documents Win32::MemoryInfo version 0.02

August 30, 2000.

=head1 AUTHOR

Chad Johnston C<<>cjohnston@rockstardevelopment.comC<>>


Copyright (C) 2000 by Chad Johnston. All rights reserved.

=head1 LICENSE

This package is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.