org.apache.tomcat.jni

Class Shm

public class Shm extends Object

Shm

Version: $Revision: 467222 $, $Date: 2006-10-24 05:17:11 +0200 (Tue, 24 Oct 2006) $

Author: Mladen Turk

Method Summary
static longattach(String filename, long pool)
Attach to a shared memory segment that was created by another process.
static longbaseaddr(long m)
Retrieve the base address of the shared memory segment.
static ByteBufferbuffer(long m)
Retrieve new ByteBuffer base address of the shared memory segment.
static longcreate(long reqsize, String filename, long pool)
Create and make accessable a shared memory segment.
static intdestroy(long m)
Destroy a shared memory segment and associated memory.
static intdetach(long m)
Detach from a shared memory segment without destroying it.
static intremove(String filename, long pool)
Remove shared memory segment associated with a filename.
static longsize(long m)
Retrieve the length of a shared memory segment in bytes.

Method Detail

attach

public static long attach(String filename, long pool)
Attach to a shared memory segment that was created by another process.

Parameters: filename The file used to create the original segment. (This MUST match the original filename.) pool the pool from which to allocate the shared memory structure for this process.

Returns: The created shared memory structure.

baseaddr

public static long baseaddr(long m)
Retrieve the base address of the shared memory segment. NOTE: This address is only usable within the callers address space, since this API does not guarantee that other attaching processes will maintain the same address mapping.

Parameters: m The shared memory segment from which to retrieve the base address.

Returns: address, aligned by APR_ALIGN_DEFAULT.

buffer

public static ByteBuffer buffer(long m)
Retrieve new ByteBuffer base address of the shared memory segment. NOTE: This address is only usable within the callers address space, since this API does not guarantee that other attaching processes will maintain the same address mapping.

Parameters: m The shared memory segment from which to retrieve the base address.

Returns: address, aligned by APR_ALIGN_DEFAULT.

create

public static long create(long reqsize, String filename, long pool)
Create and make accessable a shared memory segment.
A note about Anonymous vs. Named shared memory segments:
Not all plaforms support anonymous shared memory segments, but in some cases it is prefered over other types of shared memory implementations. Passing a NULL 'file' parameter to this function will cause the subsystem to use anonymous shared memory segments. If such a system is not available, APR_ENOTIMPL is returned.
A note about allocation sizes:
On some platforms it is necessary to store some metainformation about the segment within the actual segment. In order to supply the caller with the requested size it may be necessary for the implementation to request a slightly greater segment length from the subsystem. In all cases, the apr_shm_baseaddr_get() function will return the first usable byte of memory.

Parameters: reqsize The desired size of the segment. filename The file to use for shared memory on platforms that require it. pool the pool from which to allocate the shared memory structure.

Returns: The created shared memory structure.

destroy

public static int destroy(long m)
Destroy a shared memory segment and associated memory.

Parameters: m The shared memory segment structure to destroy.

detach

public static int detach(long m)
Detach from a shared memory segment without destroying it.

Parameters: m The shared memory structure representing the segment to detach from.

remove

public static int remove(String filename, long pool)
Remove shared memory segment associated with a filename.
This function is only supported on platforms which support name-based shared memory segments, and will return APR_ENOTIMPL on platforms without such support.

Parameters: filename The filename associated with shared-memory segment which needs to be removed pool The pool used for file operations

size

public static long size(long m)
Retrieve the length of a shared memory segment in bytes.

Parameters: m The shared memory segment from which to retrieve the segment length.

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