def __init__(self, name=None, create=False, size=0):
if not size >= 0:
raise ValueError("'size' must be a positive integer")
if create:
self._flags = _O_CREX | os.O_RDWR
if size == 0:
raise ValueError(
"'size' must be a positive number different from zero")
if name is None and not self._flags & os.O_EXCL:
raise ValueError("'name' can only be None if create=True")
if _USE_POSIX:
# POSIX Shared Memory
if name is None:
while True:
name = _make_filename()
try:
self._fd = _posixshmem.shm_open(name,
self._flags,
mode=self._mode)
except FileExistsError:
continue
self._name = name
break
else:
name = "/" + name if self._prepend_leading_slash else name
self._fd = _posixshmem.shm_open(name,
self._flags,
mode=self._mode)
self._name = name
try:
if create and size:
os.ftruncate(self._fd, size)
stats = os.fstat(self._fd)
size = stats.st_size
self._mmap = mmap.mmap(self._fd, size)
except OSError:
self.unlink()
raise
from multiprocessing.resource_tracker import register
register(self._name, "shared_memory")
else:
# Windows Named Shared Memory
if create:
while True:
temp_name = _make_filename() if name is None else name
# Create and reserve shared memory block with this name
# until it can be attached to by mmap.
h_map = _winapi.CreateFileMapping(
_winapi.INVALID_HANDLE_VALUE, _winapi.NULL,
_winapi.PAGE_READWRITE, (size >> 32) & 0xFFFFFFFF,
size & 0xFFFFFFFF, temp_name)
try:
last_error_code = _winapi.GetLastError()
if last_error_code == _winapi.ERROR_ALREADY_EXISTS:
if name is not None:
raise FileExistsError(
errno.EEXIST, os.strerror(errno.EEXIST),
name, _winapi.ERROR_ALREADY_EXISTS)
else:
continue
self._mmap = mmap.mmap(-1, size, tagname=temp_name)
finally:
_winapi.CloseHandle(h_map)
self._name = temp_name
break
else:
self._name = name
# Dynamically determine the existing named shared memory
# block's size which is likely a multiple of mmap.PAGESIZE.
h_map = _winapi.OpenFileMapping(_winapi.FILE_MAP_READ, False,
name)
try:
p_buf = _winapi.MapViewOfFile(h_map, _winapi.FILE_MAP_READ,
0, 0, 0)
finally:
_winapi.CloseHandle(h_map)
size = _winapi.VirtualQuerySize(p_buf)
self._mmap = mmap.mmap(-1, size, tagname=name)
self._size = size
self._buf = memoryview(self._mmap)
def __init__(self,
name: str = '',
size: int = 0,
readonly: bool = False,
mode: int = stat.S_IREAD | stat.S_IWRITE,
prefix: str = 'calibre-'):
if size < 0:
raise TypeError("'size' must be a non-negative integer")
if size and name:
raise TypeError('Cannot specify both name and size')
if not name:
flags = os.O_CREAT | os.O_EXCL
if not size:
raise TypeError("'size' must be > 0")
else:
flags = 0
flags |= os.O_RDONLY if readonly else os.O_RDWR
access = mmap.ACCESS_READ if readonly else mmap.ACCESS_WRITE
create = not name
tries = 30
while not name and tries > 0:
tries -= 1
q = make_filename(prefix)
if iswindows:
h_map = _winapi.CreateFileMapping(
_winapi.INVALID_HANDLE_VALUE, _winapi.NULL,
_winapi.PAGE_READONLY
if readonly else _winapi.PAGE_READWRITE,
(size >> 32) & 0xFFFFFFFF, size & 0xFFFFFFFF, q)
try:
last_error_code = _winapi.GetLastError()
if last_error_code == _winapi.ERROR_ALREADY_EXISTS:
continue
self._mmap = mmap.mmap(-1, size, tagname=q, access=access)
name = q
finally:
_winapi.CloseHandle(h_map)
else:
try:
self._fd = _posixshmem.shm_open(q, flags, mode=mode)
name = q
except FileExistsError:
continue
if tries <= 0:
raise OSError(
f'Failed to create a uniquely named SHM file, try shortening the prefix from: {prefix}'
)
self._name = name
if not create and iswindows:
h_map = _winapi.OpenFileMapping(_winapi.FILE_MAP_READ, False, name)
try:
p_buf = _winapi.MapViewOfFile(h_map, _winapi.FILE_MAP_READ, 0,
0, 0)
finally:
_winapi.CloseHandle(h_map)
size = _winapi.VirtualQuerySize(p_buf)
self._mmap = mmap.mmap(-1, size, tagname=name)
if not iswindows:
if not create:
self._fd = _posixshmem.shm_open(name, flags, mode)
try:
if flags & os.O_CREAT and size:
os.ftruncate(self._fd, size)
self.stats = os.fstat(self._fd)
size = self.stats.st_size
self._mmap = mmap.mmap(self._fd, size, access=access)
except OSError:
self.unlink()
raise
self._size = size
