File::Map - Memory mapping made simple and safe.
Version 0.19
use File::Map ':map';
map_file my $map, $filename;
if ($map ne "foobar") {
$map =~ s/bar/quz/g;
}
File::Map maps files or anonymous memory into perl variables.
This module is safe yet fast. Alternatives are either fast but can cause segfaults or loose the mapping when not used correctly, or are safe but rather slow. File::Map is as fast as a normal string yet safe.
It offers a simple interface targeted at common usage patterns
substr.File::Map supports Unix, VMS and Windows.
It has built-in support for thread synchronization.
The following functions for mapping a variable are available for exportation. They all take an lvalue as their first argument, except page_size.
Use a filehandle to map into an lvalue. *filehandle may be a bareword, constant, scalar expression, typeglob, or a reference to a typeglob. $mode uses the same format as open does. $offset and $length are byte positions in the file, and default to mapping the whole file.
Open a file and map it into an lvalue. Other than $filename, all arguments work as in map_handle.
Map an anonymous piece of memory.
Low level map operation. It accepts the same constants as map does (except its first argument obviously). If you don't know how mmap works you probably shouldn't be using this.
Flush changes made to the memory map back to disk. Mappings are always flushed when unmapped, so this is usually not necessary. If $synchronous is true and your operating system supports it, the flushing will be done synchronously.
Try to remap $lvalue to a new size. It may fail if there is not sufficient space to expand a mapping at its current location. This call is linux specific and currently not supported on other systems.
Unmap a variable. Note that normally this is not necessary, but it is included for completeness.
Disable paging for this map, thus locking it in physical memory. Depending on your operating system there may be limits on pinning.
Unlock the map from physical memory.
Advise a certain memory usage pattern. This is not implemented on all operating systems, and may be a no-op. The following values for $advice are always accepted:.
Specifies that the application has no advice to give on its behavior with respect to the mapped variable. It is the default characteristic if no advice is given.
Specifies that the application expects to access the mapped variable in a random order.
Specifies that the application expects to access the mapped variable sequentially from start to end.
Specifies that the application expects to access the mapped variable in the near future.
Specifies that the application expects that it will not access the mapped variable in the near future.
On some systems there may be more values available, but this can not be relied on. Non-existent values for $advice will be ignored.
These locking functions provide locking for threads for the mapped region. The mapped region has an internal lock and condition variable. The condition variable functions(wait_until, notify, broadcast) can only be used inside a locked block. If your perl has been compiled without thread support the condition functions will not be available.
Lock $lvalue until the end of the scope. If your perl does not support threads, this will be a no-op.
Wait for block to become true. After every failed try, wait for a signal. It returns the value returned by the block.
This will signal to one listener that the map is available.
This will signal to all listeners that the map is available.
These constants are used for sys_map. If you think you need them your mmap manpage will explain them, but in most cases you can skip sys_map altogether.
All previously mentioned functions are available for exportation, but none are exported by default. Some functions may not be available on your OS or your version of perl as specified above. A number of tags are defined to make importation easier.
map_handle, map_file, map_anonymous, sys_map, unmap
remap, sync, pin, unpin, advise
lock_map, wait_until, notify, broadcast
PROT_NONE, PROT_READ, PROT_WRITE, PROT_EXEC, MAP_ANONYMOUS, MAP_SHARED, MAP_PRIVATE, MAP_ANON, MAP_FILE
If you use warnings, this module will give warnings if the variable is improperly used (anything that changes its size). This can be turned off lexically by using no warnings 'substr'.
If an error occurs in any of these functions, an exception will be thrown. In particular; trying to sync, remap, unmap, pin, unpin, advise or lock_map a variable that hasn't been mapped will cause an exception to be thrown.
This module does not have any dependencies on non-standard modules.
You probably don't want to use > as a mode. This does not give you reading permissions on many architectures, resulting in segmentation faults (confusingly, it will work on some others).
As any piece of software, bugs are likely to exist here. Bug reports are welcome.
Please report any bugs or feature requests to bug-file-map at rt.cpan.org, or through the web interface at http://rt.cpan.org/NoAuth/ReportBug.html?Queue=File-Map. I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.
Leon Timmermans, <leont at cpan.org>
You can find documentation for this module with the perldoc command.
perldoc File::Map
You can also look for information at:
Copyright 2008, 2009 Leon Timmermans, all rights reserved.
This program is free software; you can redistribute it and/or modify it under the same terms as perl itself.
