C++ MapViewOfFileEx函数代码示例

    void* MemoryMappedFile::remapPrivateView(void *oldPrivateAddr) {
        verify( Lock::isW() );

        LockMongoFilesExclusive lockMongoFiles;

        RemapLock lk;   // Interlock with PortMessageServer::acceptedMP() to stop thread creation

        clearWritableBits(oldPrivateAddr);
        if( !UnmapViewOfFile(oldPrivateAddr) ) {
            DWORD dosError = GetLastError();
            log() << "UnMapViewOfFile for " << filename()
                    << " failed with error " << errnoWithDescription( dosError )
                    << " in MemoryMappedFile::remapPrivateView"
                    << endl;
            fassertFailed( 16168 );
        }

        void* newPrivateView = MapViewOfFileEx(
                maphandle,          // file mapping handle
                FILE_MAP_READ,      // access
                0, 0,               // file offset, high and low
                0,                  // bytes to map, 0 == all
                oldPrivateAddr );   // we want the same address we had before
        if ( 0 == newPrivateView ) {
            DWORD dosError = GetLastError();
            log() << "MapViewOfFileEx for " << filename()
                    << " failed with error " << errnoWithDescription( dosError )
                    << " (file size is " << len << ")"
                    << " in MemoryMappedFile::remapPrivateView"
                    << endl;
        }
        fassert( 16148, newPrivateView == oldPrivateAddr );
        return newPrivateView;
    }

LPVOID DL_MapViewOfFileExNuma(HANDLE hFileMappingObject, DWORD dwDesiredAccess, DWORD dwFileOffsetHigh, DWORD dwFileOffsetLow, SIZE_T dwNumberOfBytesToMap, LPVOID lpBaseAddress, DWORD nndPreferred)
{
    typedef LPVOID (WINAPI * MapViewOfFileExNuma_t)(HANDLE, DWORD, DWORD, DWORD, SIZE_T, LPVOID, DWORD);
    static auto fcn = (MapViewOfFileExNuma_t)GetKernelProcAddress("MapViewOfFileExNuma");
    if (not fcn) return MapViewOfFileEx(hFileMappingObject, dwDesiredAccess, dwFileOffsetHigh, dwFileOffsetLow, dwNumberOfBytesToMap, lpBaseAddress);
    return fcn(hFileMappingObject, dwDesiredAccess, dwFileOffsetHigh, dwFileOffsetLow, dwNumberOfBytesToMap, lpBaseAddress, nndPreferred);
}

/* mmap(NULL, size, PROT_READ, MAP_SHARED, fd, 0); */
void *mmap(void *start, size_t length, int prot, int flags, int fd, off_t offset) {
    HANDLE h;
    void *data;

    (void) offset;

    if ((flags != MAP_SHARED) || (prot != PROT_READ)) {
        /*  Not supported  in this port */
        return MAP_FAILED;
    };

    h = CreateFileMapping((HANDLE) FDAPI_get_osfhandle(fd), NULL, PAGE_READONLY, 0, 0, NULL);
    if (!h) {
        return MAP_FAILED;
    }

    data = MapViewOfFileEx(h, FILE_MAP_READ, 0, 0, length, start);
    CloseHandle(h);

    if (!data) {
        return MAP_FAILED;
    }

    return data;
}

/*
In order to create a new message queue, or access an existing queue, the shmget() system call is used.

  SYSTEM CALL: shmget();                                                          

  PROTOTYPE: int shmget ( key_t key, int size, int shmflg );                                             
    RETURNS: shared memory segment identifier on success                                                       
             -1 on error: errno = EINVAL (Invalid segment size specified)
                                  EEXIST (Segment exists, cannot create)
                                  EIDRM (Segment is marked for deletion, or was removed)
                                  ENOENT (Segment does not exist)
                                  EACCES (Permission denied)
                                  ENOMEM (Not enough memory to create segment)
  NOTES:
This particular call should almost seem like old news at this point. 
It is strikingly similar to the corresponding get calls for message queues and semaphore sets.
The first argument to shmget() is the key value (in our case returned by a call to ftok()). 
This key value is then compared to existing key values that exist within the kernel for other shared memory segments. 
At that point, the open or access operation is dependent upon the contents of the shmflg argument.

IPC_CREAT
Create the segment if it doesn't already exist in the kernel.

IPC_EXCL
When used with IPC_CREAT, fail if segment already exists.

If IPC_CREAT is used alone, shmget() either returns the segment identifier for a newly created segment, 
or returns the identifier for a segment which exists with the same key value. 
If IPC_EXCL is used along with IPC_CREAT, then either a new segment is created, or if the segment exists, the call fails with -1. 
IPC_EXCL is useless by itself, but when combined with IPC_CREAT, it can be used as a facility to guarantee that no existing segment is opened for access.

Once again, an optional octal mode may be OR'd into the mask.

Let's create a wrapper function for locating or creating a shared memory segment :

int open_segment( key_t keyval, int segsize )
{
        int     shmid;
        
        if((shmid = shmget( keyval, segsize, IPC_CREAT | 0660 )) == -1)
        {
                return(-1);
        }
        
        return(shmid);
}
Note the use of the explicit permissions of 0660. 
This small function either returns a shared memory segment identifier (int), or -1 on error. 
The key value and requested segment size (in bytes) are passed as arguments.
Once a process has a valid IPC identifier for a given segment, the next step is for the process to attach or map the segment into its own addressing space.
*/ 
TSRM_API int shmget ( key_t key, int size, int shmflg ) { //int shmget(int key, int size, int flags) {
	shm_pair *shm;
	char shm_segment[26], shm_info[29];
	HANDLE shm_handle, info_handle;
	BOOL created = FALSE;
	DWORD errnum;	//for DEBUG

	if (size < 0) {
		return -1;
	}

	sprintf(shm_segment, "TSRM_SHM_SEGMENT:%d", key);
	sprintf(shm_info, "TSRM_SHM_DESCRIPTOR:%d", key);

	shm_handle  = OpenFileMapping(FILE_MAP_ALL_ACCESS, FALSE, shm_segment);
	info_handle = OpenFileMapping(FILE_MAP_ALL_ACCESS, FALSE, shm_info);

	if ((!shm_handle && !info_handle)) {
		if (shmflg & IPC_CREAT) {
			shm_handle	= CreateFileMapping(INVALID_HANDLE_VALUE, NULL, PAGE_READWRITE, 0, size, shm_segment);
			info_handle	= CreateFileMapping(INVALID_HANDLE_VALUE, NULL, PAGE_READWRITE, 0, sizeof(shm->descriptor), shm_info);
			created		= TRUE;
		}
		if ((!shm_handle || !info_handle)) {
			errnum = GetLastError();
			return -1;
		}
	} else {
		if (shmflg & IPC_EXCL) {
			return -1;
		}
	}
	
	if ((shm = shm_get(CREATE_NEW_IF_NOT_EXISTS, key, NULL)) == NULL)	return -1;
	shm->segment = shm_handle;
	shm->info	 = info_handle;
	shm->descriptor = MapViewOfFileEx(shm->info, FILE_MAP_ALL_ACCESS, 0, 0, 0, NULL);

	if (created) {
		shm->descriptor->shm_perm.key	= key;
		shm->descriptor->shm_segsz		= size;
		shm->descriptor->shm_ctime		= time(NULL);
		shm->descriptor->shm_cpid		= getpid();
		shm->descriptor->shm_perm.mode	= shmflg;

		shm->descriptor->shm_perm.cuid	= shm->descriptor->shm_perm.cgid= 0;
		shm->descriptor->shm_perm.gid	= shm->descriptor->shm_perm.uid = 0;
		shm->descriptor->shm_atime		= shm->descriptor->shm_dtime	= 0;
		shm->descriptor->shm_lpid		= shm->descriptor->shm_nattch	= 0;
//.........这里部分代码省略.........

void* MemArena::CreateViewAt(s64 offset, size_t size, void* base)
{
#ifdef _WIN32
	return MapViewOfFileEx(hMemoryMapping, FILE_MAP_ALL_ACCESS, 0, (DWORD)((u64)offset), size, base);
#else
	return mmap(base, size, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_FIXED, fd, offset);
#endif
}

/* A template function which creates/attaches shm seg handle
 * to the shared memory. Used by user-exposed functions below
 */
static inline int MPL_shm_seg_create_attach_templ(MPL_shm_hnd_t hnd, intptr_t seg_sz,
                                                  void **shm_addr_ptr, int offset, int flag)
{
    HANDLE lhnd = INVALID_HANDLE_VALUE;
    int rc = MPL_SHM_SUCCESS;
    ULARGE_INTEGER seg_sz_large;
    seg_sz_large.QuadPart = seg_sz;

    if (!MPLI_shm_ghnd_is_valid(hnd)) {
        rc = MPLI_shm_ghnd_set_uniq(hnd);
        if (rc) {
            goto fn_exit;
        }
    }

    if (flag & MPLI_SHM_FLAG_SHM_CREATE) {
        lhnd = CreateFileMapping(INVALID_HANDLE_VALUE, NULL,
                                 PAGE_READWRITE, seg_sz_large.HighPart, seg_sz_large.LowPart,
                                 MPLI_shm_ghnd_get_by_ref(hnd));
        if (lhnd == NULL) {
            rc = MPL_SHM_EINTERN;
            goto fn_exit;
        }
        MPLI_shm_lhnd_set(hnd, lhnd);
    } else {
        if (!MPLI_shm_lhnd_is_valid(hnd)) {
            /* Strangely OpenFileMapping() returns NULL on error! */
            lhnd = OpenFileMapping(FILE_MAP_WRITE, FALSE, MPLI_shm_ghnd_get_by_ref(hnd));
            if (lhnd == NULL) {
                rc = MPL_SHM_EINTERN;
                goto fn_exit;
            }

            MPLI_shm_lhnd_set(hnd, lhnd);
        }
    }

    if (flag & MPLI_SHM_FLAG_SHM_ATTACH) {
        if (flag & MPLI_SHM_FLAG_FIXED_ADDR) {
            void *start_addr = (void *) *shm_addr_ptr;
            /* The start_addr must be a multiple of the system's memory allocation granularity,
             * or the function fails. To determine the memory allocation granularity of the system,
             * use the GetSystemInfo function. If there is not enough address space at the
             * specified address, the function fails.
             * If the function fails, the return value is NULL.*/
            *shm_addr_ptr = MapViewOfFileEx(MPLI_shm_lhnd_get(hnd),
                                            FILE_MAP_WRITE, 0, offset, 0, start_addr);
        } else {
            *shm_addr_ptr = MapViewOfFile(MPLI_shm_lhnd_get(hnd), FILE_MAP_WRITE, 0, offset, 0);
        }
        if (*shm_addr_ptr == NULL) {
            rc = MPL_SHM_EINVAL;
        }
    }

  fn_exit:
    return rc;
}

APIRET os2APIENTRY DosGetSharedMem(PVOID pb,
                                   ULONG flag)
{
        if(!pb)
                return 487; //error_invalid_address
        if(flag&(PAG_READ|PAG_WRITE|PAG_EXECUTE|PAG_GUARD)!=flag)
                return 87; //error_invalid_parameter

        PoolLock pl;
        SM_Pool *ppool=lockPool(&pl);

        for(int i=0; i<MAXSHAREDMEMOBJECTS; i++)
                if(ppool->SM_Object[i].SM_ReferenceCount && ppool->SM_Object[i].SM_BaseAddress==(DWORD)pb)
                        break;
        if(i>=MAXSHAREDMEMOBJECTS) {
                unlockPool(&pl);
                return 487; //error_invalid_address
        }

        if(hFileMapping[i]!=NULL) {
                //already mapped
                unlockPool(&pl);
                return 0;
        }
        
        //open file mapping
        hFileMapping[i] = OpenFileMapping(flag&PAG_WRITE?FILE_MAP_WRITE:FILE_MAP_READ,
                                          FALSE,
                                          ppool->SM_Object[i].SM_Filemapname
                                         );
        if(hFileMapping[i]==NULL) {
                unlockPool(&pl);
                return 8; //error_not_enough_memory
        }
        
        //map
        unreserveObjectAddresses(i);
        LPVOID lpv = MapViewOfFileEx(hFileMapping[i],
                                     flag&PAG_WRITE ? FILE_MAP_WRITE:FILE_MAP_READ,
                                     0,0,
                                     (DWORD)ppool->SM_Object[i].SM_Size,
                                     (LPVOID)ppool->SM_Object[i].SM_BaseAddress
                                    );
        if((DWORD)lpv!=ppool->SM_Object[i].SM_BaseAddress) {
                //nt didn't like it
                reserveObjectAddresses(i);
                CloseHandle(hFileMapping[i]);
                hFileMapping[i]=NULL;
                return 8; //error_not_enough_memory
        }

        unlockPool(&pl);
        return 0;
}

    void* MemoryMappedFile::remapPrivateView(void *oldPrivateAddr) {
        bool ok = UnmapViewOfFile(oldPrivateAddr);
        assert(ok);

        // we want the new address to be the same as the old address in case things keep pointers around (as namespaceindex does).
        void *p = MapViewOfFileEx(maphandle, FILE_MAP_COPY, 0, 0, 
                                  /*dwNumberOfBytesToMap 0 means to eof*/0 /*len*/,
                                  oldPrivateAddr);
        assert(p);
        assert(p == oldPrivateAddr);
        return p;
    }

void *shmat(int shmid, LPVOID shmaddr, int shmflg)
{
    struct shmid_ds *shm = &shmids[shmid];

    if(shm->addr == shmaddr )
	return shm->addr;
    shm->addr = MapViewOfFileEx (shm->filemapping, FILE_MAP_WRITE, 0, 0, shm->size, shmaddr);
    if (addr == NULL)
	win32_error("MapViewOfFileEx %08X", shmaddr);
    write_log ("shmat %08X -> %08X\n", shmaddr, shm->addr);
    shm->attached = 1;
    return shm->addr;
}

BOOL My_MapViewOfFileEx()
{
	HANDLE hFileMappingObject=NULL;
	DWORD dwDesiredAccess=NULL;
	DWORD dwFileOffsetHigh=NULL;
	DWORD dwFileOffsetLow=NULL;
	SIZE_T dwNumberOfBytesToMap=NULL;
	LPVOID lpBaseAddress=NULL;
	LPVOID returnVal_Real = NULL;
	LPVOID returnVal_Intercepted = NULL;

	DWORD error_Real = 0;
	DWORD error_Intercepted = 0;
	__try{
	disableInterception();
	returnVal_Real = MapViewOfFileEx (hFileMappingObject,dwDesiredAccess,dwFileOffsetHigh,dwFileOffsetLow,dwNumberOfBytesToMap,lpBaseAddress);
	error_Real = GetLastError();
	enableInterception();
	returnVal_Intercepted = MapViewOfFileEx (hFileMappingObject,dwDesiredAccess,dwFileOffsetHigh,dwFileOffsetLow,dwNumberOfBytesToMap,lpBaseAddress);
	error_Intercepted = GetLastError();
	}__except(puts("in filter"), 1){puts("exception caught");}
	return ((returnVal_Real == returnVal_Intercepted) && (error_Real == error_Intercepted));
}

int File::mmread()
{
#if POSIX
    return read();
#elif _WIN32
    HANDLE hFile;
    HANDLE hFileMap;
    DWORD size;
    char *name;

    name = this->name->toChars();
    hFile = CreateFile(name, GENERIC_READ,
                        FILE_SHARE_READ, NULL,
                        OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
    if (hFile == INVALID_HANDLE_VALUE)
        goto Lerr;
    size = GetFileSize(hFile, NULL);
    //printf(" file created, size %d\n", size);

    hFileMap = CreateFileMapping(hFile,NULL,PAGE_READONLY,0,size,NULL);
    if (CloseHandle(hFile) != TRUE)
        goto Lerr;

    if (hFileMap == NULL)
        goto Lerr;

    //printf(" mapping created\n");

    if (!ref)
        mem.free(buffer);
    ref = 2;
    buffer = (utf8_t *)MapViewOfFileEx(hFileMap, FILE_MAP_READ,0,0,size,NULL);
    if (CloseHandle(hFileMap) != TRUE)
        goto Lerr;
    if (buffer == NULL)                 // mapping view failed
        goto Lerr;

    len = size;
    //printf(" buffer = %p\n", buffer);

    return 0;

Lerr:
    return GetLastError();                      // failure
#else
    assert(0);
#endif
}

TSRM_API void *shmat(int key, const void *shmaddr, int flags)
{
	shm_pair *shm = shm_get(key, NULL);

	if (!shm->segment) {
		return (void*)-1;
	}

	shm->descriptor->shm_atime = time(NULL);
	shm->descriptor->shm_lpid  = getpid();
	shm->descriptor->shm_nattch++;

	shm->addr = MapViewOfFileEx(shm->segment, FILE_MAP_ALL_ACCESS, 0, 0, 0, NULL);

	return shm->addr;
}

/*
  SYSTEM CALL: shmat();                                                          

  PROTOTYPE: int shmat ( int shmid, char *shmaddr, int shmflg);
    RETURNS: address at which segment was attached to the process, or
             -1 on error: errno = EINVAL (Invalid IPC ID value or attach address passed)
                                  ENOMEM (Not enough memory to attach segment)
                                  EACCES (Permission denied)
  NOTES:
If the addr argument is zero (0), the kernel tries to find an unmapped region. 
This is the recommended method. 
An address can be specified, but is typically only used to facilitate proprietary hardware 
or to resolve conflicts with other apps. 
The SHM_RND flag can be OR'd into the flag argument to force a passed address to be page aligned (rounds down to the nearest page size).
In addition, if the SHM_RDONLY flag is OR'd in with the flag argument, then the shared memory segment will be mapped in, but marked as readonly.

This call is perhaps the simplest to use. 
Consider this wrapper function, which is passed a valid IPC identifier for a segment, and returns the address that the segment was attached to:

char *attach_segment( int shmid )
{
        return(shmat(shmid, 0, 0));
}
Once a segment has been properly attached, and a process has a pointer to the start of that segment, 
reading and writing to the segment become as easy as simply referencing or dereferencing the pointer! 
Be careful not to lose the value of the original pointer! If this happens, you will have no way of accessing the base (start) of the segment.
*/
TSRM_API void *shmat(int shmid, const void *shmaddr, int shmflg) {	//void *shmat(int key, const void *shmaddr, int flags) {
	shm_pair *shm;
	if ((shm = shm_get(GET_IF_EXISTS_BY_KEY, shmid, NULL)) == NULL)	return (void*)-1;
	
	if (!shm->segment) {
		return (void*)-1;
	}

	shm->descriptor->shm_atime = time(NULL);
	shm->descriptor->shm_lpid  = getpid();
	shm->descriptor->shm_nattch++;

	shm->addr = MapViewOfFileEx(shm->segment, FILE_MAP_ALL_ACCESS, 0, 0, 0, NULL);

	return shm->addr;
}

/*
 * @implemented
 */
LPVOID
NTAPI
MapViewOfFile(HANDLE hFileMappingObject,
              DWORD dwDesiredAccess,
              DWORD dwFileOffsetHigh,
              DWORD dwFileOffsetLow,
              SIZE_T dwNumberOfBytesToMap)
{
    /* Call the extended API */
    return MapViewOfFileEx(hFileMappingObject,
                           dwDesiredAccess,
                           dwFileOffsetHigh,
                           dwFileOffsetLow,
                           dwNumberOfBytesToMap,
                           NULL);
}

int MmapFile::open(const char* fileName) {
  int filedes = ::open(fileName, O_RDONLY);
  if (filedes < 0) {
    REprintf("Cannot open file");
    // exit(1);
    return -1;
  }
  this->fileSize = ::getFileSize(fileName);
  if (data) {
    this->close();
  }
#ifndef _WIN32
  this->data = mmap(0, this->fileSize, PROT_READ, MAP_SHARED, filedes, 0);
  if (this->data == MAP_FAILED) {
    REprintf("mmap() failed!");
    // exit(1);
    return -1;
  }
#else
  // see:
  // http://courses.washington.edu/hypertxt/cwb/cl/windows-mmap.c
  // https://docs.microsoft.com/en-us/windows/desktop/api/winbase/nf-winbase-createfilemappinga
  this->handle = CreateFileMapping(
      (HANDLE)_get_osfhandle(filedes),
      NULL,  //  the file mapping object gets a default security descriptor
      PAGE_READONLY,  // can also be PAGE_WRITECOPY,
      0,  // dwMaximumSizeHigh are 0 (zero), the maximum size of the file
          // mapping object is equal to the current size of the file that hFile
          // identifies
      0,  // dwMaximumSizeLow (see above)
      NULL);  // lpName = NULL, the file mapping object is created without a
              // name.
  if (handle == NULL) {
    return -1;
  }
  this->data = MapViewOfFileEx(handle, FILE_MAP_READ,
                               0,  // dwFileOffsetHigh: The high-order DWORD of
                                   // the file offset where the view is to begin
                               0,  // dwFileOffsetLow: see above
                               this->fileSize,  // dwNumberOfBytesToMap
                               NULL);  // lpBaseAddress: A pointer to the memory
                                       // address in the calling process address
                                       // space where mapping begins.

#endif
  return 0;
}