Name
Data::Layout::BuddySystem - Layout data in memory allocated via a buddy system
Synopsis
use Test::More tests=>10;
use Data::Layout::BuddySystem;
use utf8;
my $b = Data::Layout::BuddySystem::new; # Create a new buddy system
$b->allocField(@$_) for # Allocate fields in the buddy system
[𝝳=>6], [𝝰=>0], [𝝙=>6],[𝝱=>0],[𝞈 =>4], [𝝺=>5], [𝝲=>0], [𝝖=>3], [𝝗=>3]; # Name and log2 size of each field
my $s = $b->generateStructureFields('Struct'); # Generate structure definition
ok nws($s->()) eq nws(<<'END'); # String representation of methods associated with generated structure
package Struct;
use utf8;
sub 𝝰 :lvalue {vec($_[1], 0, 1 )}
sub 𝝱 :lvalue {vec($_[1], 1, 1 )}
sub 𝝲 :lvalue {vec($_[1], 2, 1 )}
sub 𝝖 :lvalue {vec($_[1], 1, 8 )}
sub 𝝗 :lvalue {vec($_[1], 2, 8 )}
sub 𝞈 :lvalue {vec($_[1], 2, 16 )}
sub 𝝺 :lvalue {vec($_[1], 2, 32 )}
sub 𝝳 :lvalue {vec($_[1], 2, 64 )}
sub 𝝙 :lvalue {vec($_[1], 3, 64 )}
END
if (1) # Set fields
{$s->𝝰(my $𝕄) = 1; ok $𝕄 eq "\1";
$s->𝝱( $𝕄) = 0; ok $𝕄 eq "\1";
$s->𝝲( $𝕄) = 1; ok $𝕄 eq "\5";
$s->𝝖( $𝕄) = 3; ok $𝕄 eq "\x05\x03"; # Byte fields
$s->𝝗( $𝕄) = 7; ok $𝕄 eq "\x05\x03\x07";
$s->𝞈( $𝕄) = 9; ok $𝕄 eq "\x05\x03\x07\x00\x00\x09"; # Word field
}
if (1) # Set and get an integer field
{$s->𝝺(my $𝕄) = 2; ok $s->𝝺($𝕄) == 2; # Set field
$s->𝝺( $𝕄)++; ok $s->𝝺($𝕄) == 3; # Increment field
ok $𝕄 eq "\0\0\0\0\0\0\0\0\0\0\0\3"; # Dump the memory organised by the buddy system
}Description
Implements the buddy system described at https://en.wikipedia.org/wiki/Buddy_memory_allocation in 100% Pure Perl. Blocks can be identified by names or addresses which remain invariant even after one buddy system has been copied to a new one to compact free space. Each named allocation can be accessed via a generated method which identifies an lvalue area of a "vec" in perlfunc string used to back the memory organised by the buddy system.
Methods
new()
Create a new Buddy system
allocField($buddySystem, $name, $size)
Allocate a block in the buddy system, give it a name that is invariant even after this buddy system has been copied to a new buddy system to compact its storage, and return the address of its location in the buddy system
Parameter Description
1 $buddySystem Buddy system
2 $name name of block
3 $size integer log2(size of allocation)alloc($buddySystem, $size)
Allocate a block and return its address
Parameter Description
1 $buddySystem Buddy system
2 $size integer log2(size of allocation)locateAddress($buddySystem, $alloc)
Find the current location of a block by its original address after it has been copied to a new buddy system
Parameter Description
1 $buddySystem Buddy system
2 $alloc address at which the block was originally locatedlocateName($buddySystem, $name)
Find the current location of a named block after it has been copied to a new buddy system
Parameter Description
1 $buddySystem Buddy system
2 $name name of the blockfreeName($buddySystem, $name)
Free an allocated block via its name
Parameter Description
1 $buddySystem Buddy system
2 $name name used to allocate blockfree($buddySystem, $alloc)
Free an allocation via its original allocation address
Parameter Description
1 $buddySystem Buddy system
2 $alloc original allocation addressStatistics
These methods provide statistics on memory usage in the buddy system
usedSpace($buddySystem)
Total allocated space in this buddy system
Parameter Description
1 $buddySystem Buddy systemfreeSpace($buddySystem)
Total free space that can still be allocated in this buddy system without changing its size
Parameter Description
1 $buddySystem Buddy systemtotalSpace($buddySystem)
Total space currently occupied by this buddy system
Parameter Description
1 $buddySystem Buddy systemRelocation
These methods copy one buddy system to another compacting free space in the process.
copy($buddySystem, $order, $copy)
Copy a buddy system to compact its free space, the largest blocks are placed in (0) - ascending, (1) - descending order of size, blocks that get relocated to new positions in the new buddy system will still be accessible by their original address or name
Parameter Description
1 $buddySystem Buddy system
2 $order order
3 $copy optional copy method to copy an old allocation into its corresponding new allocationcopyLargestLast($buddySystem, $copy)
Copy a buddy system, compacting free space, the new addresses of allocations can be found in wentTo, the largest blocks are placed last
Parameter Description
1 $buddySystem BuddySystem
2 $copy copy method to copy an old allocation into a new allocationcopyLargestFirst($buddySystem, $copy)
Copy a buddy system, compacting free space, the new addresses of allocations can be found in wentTo, the largest blocks are placed first
Parameter Description
1 $buddySystem BuddySystem
2 $copy copy method to copy an old allocation into a new allocationStructure
This method generates a blessed sub whose methods provide named access to allocations backed by a "vec" in perlfunc string
generateStructureFields($buddySystem, $package)
Return a blessed sub whose methods access the named blocks in the buddy system. The blessed sub returns a text representation of the method definitions
Parameter Description
1 $buddySystem Buddy system
2 $package structure nameIndex
The following methods will be exported by the :all tag
"alloc($buddySystem, $size)" "allocField($buddySystem, $name, $size)" "copy($buddySystem, $order, $copy)" "copyLargestFirst($buddySystem, $copy)" "copyLargestLast($buddySystem, $copy)" "free($buddySystem, $alloc)" "freeName($buddySystem, $name)" "freeSpace($buddySystem)" "generateStructureFields($buddySystem, $package)" "locateAddress($buddySystem, $alloc)" "locateName($buddySystem, $name)" "new()" "totalSpace($buddySystem)" "usedSpace($buddySystem)"
Installation
This module is written in 100% Pure Perl and is thus easy to read, modify and install.
Standard Module::Build process for building and installing modules:
perl Build.PL
./Build
./Build test
./Build installAuthor
philiprbrenan@gmail.com
http://www.appaapps.com
Copyright
Copyright (c) 2016 Philip R Brenan.
This module is free software. It may be used, redistributed and/or modified under the same terms as Perl itself.