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/** @file
* IPRT - Named shared memory.
*/
/*
* Copyright (C) 2018-2025 Oracle and/or its affiliates.
*
* This file is part of VirtualBox base platform packages, as
* available from https://www.virtualbox.org.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation, in version 3 of the
* License.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, see <https://www.gnu.org/licenses>.
*
* The contents of this file may alternatively be used under the terms
* of the Common Development and Distribution License Version 1.0
* (CDDL), a copy of it is provided in the "COPYING.CDDL" file included
* in the VirtualBox distribution, in which case the provisions of the
* CDDL are applicable instead of those of the GPL.
*
* You may elect to license modified versions of this file under the
* terms and conditions of either the GPL or the CDDL or both.
*
* SPDX-License-Identifier: GPL-3.0-only OR CDDL-1.0
*/
#ifndef IPRT_INCLUDED_shmem_h
#define IPRT_INCLUDED_shmem_h
#ifndef RT_WITHOUT_PRAGMA_ONCE
# pragma once
#endif
#include <iprt/types.h>
RT_C_DECLS_BEGIN
/** @defgroup grp_rt_shmem RTShMem - Shared memory.
* @ingroup grp_rt
* @{
*/
/** @name Open flags for RTShMemOpen().
* @{
*/
/** Creates a new shared memory object or opens an already existing one. */
#define RTSHMEM_O_F_CREATE RT_BIT_32(0)
/** Creates a new shared memory object failing if one with the same name exists already. */
#define RTSHMEM_O_F_CREATE_EXCL (RTSHMEM_O_F_CREATE | RT_BIT_32(1))
/** Opens the shared memory object for read access. */
#define RTSHMEM_O_F_READ RT_BIT_32(2)
/** Opens the shared memory object for write access. */
#define RTSHMEM_O_F_WRITE RT_BIT_32(3)
/** Opens the shared memory object for read and write access. */
#define RTSHMEM_O_F_READWRITE (RTSHMEM_O_F_READ | RTSHMEM_O_F_WRITE)
/** Truncates the shared memory object to 0 bytes on open. */
#define RTSHMEM_O_F_TRUNCATE RT_BIT_32(4)
/** Mappings may be created with executable access right (required to be known on Windows beforehand). */
#define RTSHMEM_O_F_MAYBE_EXEC RT_BIT_32(5)
/** Mask of all valid flags. */
#define RTSHMEM_O_F_VALID_MASK UINT32_C(0x0000003f)
/** @} */
/**
* Creates or opens a new shared memory object with the given name.
*
* @returns IPRT status code.
* @retval VERR_OUT_OF_RANGE if the mapping hint count is too big.
* @param phShMem Where to store the handle to the shared memory object on success.
* @param pszName Name of the shared memory object to open or create.
* @param fFlags Combination of RTSHMEM_O_F_* flags.
* @param cbMax Maximum number of bytes to reserve for the shared memory object.
* On some platforms this can be 0 and set to another value using RTShMemSetSize() afterwards.
* Giving 0 on Windows results in an error as shared memory objects there do not support
* changing the size afterwards.
* @param cMappingsHint Hint about the possible number of mappings created later on, set to 0 for a default value.
*/
RTDECL(int) RTShMemOpen(PRTSHMEM phShMem, const char *pszName, uint32_t fFlags, size_t cbMax, uint32_t cMappingsHint);
/**
* Closes the given shared memory object.
*
* @returns IPRT status code.
* @retval VERR_INVALID_STATE if there is still a mapping active for the given shared memory object.
* @param hShMem The shared memory object handle.
*
* @note The shared memory object will be deleted if the creator closes it.
*/
RTDECL(int) RTShMemClose(RTSHMEM hShMem);
/**
* Tries to delete a shared memory object with the given name.
*
* @returns IPRT status code.
* @retval VERR_NOT_SUPPORTED if the platform does not support deleting the shared memory object by name.
* @param pszName Name of the shared memory object to delete.
*/
RTDECL(int) RTShMemDelete(const char *pszName);
/**
* Returns the number of references (i.e. mappings) held for the given shared memory object.
*
* @returns Reference count or 0 on invalid handle.
* @param hShMem The shared memory object handle.
*/
RTDECL(uint32_t) RTShMemRefCount(RTSHMEM hShMem);
/**
* Sets the size of the given shared memory object.
*
* @returns IPRT status code.
* @retval VERR_INVALID_STATE if there are mappings active for the given shared memory object.
* @retval VERR_NOT_SUPPORTED on some hosts which do not support changing the size after creation.
* @param hShMem The shared memory object handle.
* @param cbMem Size of the memory object handle in bytes.
*/
RTDECL(int) RTShMemSetSize(RTSHMEM hShMem, size_t cbMem);
/**
* Queries the current size of the shared memory object.
*
* @returns IPRT status code.
* @param hShMem The shared memory object handle.
* @param pcbMem Where to store the size of the shared memory object on success.
*/
RTDECL(int) RTShMemQuerySize(RTSHMEM hShMem, size_t *pcbMem);
/** @name Region mapping flags for RTShMemMapRegion().
* @{
*/
/** Read access. */
#define RTSHMEM_MAP_F_READ RT_BIT_32(0)
/** Write access. */
#define RTSHMEM_MAP_F_WRITE RT_BIT_32(1)
/** Execute access. */
#define RTSHMEM_MAP_F_EXEC RT_BIT_32(2)
/** Copy on write, any write creates a new page private to the callers address space and changes
* in that area are not shared with other processes using the hsared memory object. */
#define RTSHMEM_MAP_F_COW RT_BIT_32(3)
/** Mask of all valid flags. */
#define RTSHMEM_MAP_F_VALID_MASK UINT32_C(0x0000000f)
/** @} */
/**
* Maps a region of the given shared memory object into the callers address space.
*
* @returns IPRT status code.
* @retval VERR_SHMEM_MAXIMUM_MAPPINGS_REACHED if the maximum number of mappings was reached (host dependent).
* @retval VERR_ACCESS_DENIED if the requested memory access rights do not line up with the flags given when opening
* the memory object (requesting write access for a readonly shared memory object for example).
* @param hShMem The shared memory object handle.
* @param offRegion Offset into the shared memory object to start mapping at.
* @param cbRegion Size of the region to map.
* @param fFlags Desired properties of the mapped region, combination of RTSHMEM_MAP_F_* defines.
* @param ppv Where to store the start address of the mapped region on success.
*/
RTDECL(int) RTShMemMapRegion(RTSHMEM hShMem, size_t offRegion, size_t cbRegion, uint32_t fFlags, void **ppv);
/**
* Unmaps the given region of the shared memory object.
*
* @returns IPRT status code.
* @param hShMem The shared memory object handle.
* @param pv Pointer to the mapped region obtained with RTShMemMapRegion() earlier on.
*/
RTDECL(int) RTShMemUnmapRegion(RTSHMEM hShMem, void *pv);
/** @} */
RT_C_DECLS_END
#endif /* !IPRT_INCLUDED_shmem_h */
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