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__all__ = ['memmap']
import mmap
from numeric import uint8, ndarray, dtype
dtypedescr = dtype
valid_filemodes = ["r", "c", "r+", "w+"]
writeable_filemodes = ["r+","w+"]
mode_equivalents = {
"readonly":"r",
"copyonwrite":"c",
"readwrite":"r+",
"write":"w+"
}
class memmap(ndarray):
__array_priority__ = -100.0
def __new__(subtype, name, dtype=uint8, mode='r+', offset=0,
shape=None, order='C'):
try:
mode = mode_equivalents[mode]
except KeyError:
if mode not in valid_filemodes:
raise ValueError("mode must be one of %s" % \
(valid_filemodes + mode_equivalents.keys()))
fid = file(name, (mode == 'c' and 'r' or mode)+'b')
if (mode == 'w+') and shape is None:
raise ValueError, "shape must be given"
fid.seek(0,2)
flen = fid.tell()
descr = dtypedescr(dtype)
_dbytes = descr.itemsize
if shape is None:
bytes = flen-offset
if (bytes % _dbytes):
fid.close()
raise ValueError, "Size of available data is not a "\
"multiple of data-type size."
size = bytes // _dbytes
shape = (size,)
else:
if not isinstance(shape, tuple):
shape = (shape,)
size = 1
for k in shape:
size *= k
bytes = long(offset + size*_dbytes)
if mode == 'w+' or (mode == 'r+' and flen < bytes):
fid.seek(bytes-1,0)
fid.write(chr(0))
fid.flush()
if mode == 'c':
acc = mmap.ACCESS_COPY
elif mode == 'r':
acc = mmap.ACCESS_READ
else:
acc = mmap.ACCESS_WRITE
mm = mmap.mmap(fid.fileno(), bytes, access=acc)
self = ndarray.__new__(subtype, shape, dtype=descr, buffer=mm,
offset=offset, order=order)
self._mmap = mm
self._offset = offset
self._mode = mode
self._size = size
self._name = name
fid.close()
return self
def __array_finalize__(self, obj):
if obj is not None and not isinstance(obj, memmap):
raise ValueError, "Cannot create a memmap array that way"
self._mmap = None
def sync(self):
self._mmap.flush()
def close(self):
self._mmap.close()
def __del__(self):
if self._mmap is not None:
self._mmap.flush()
del self._mmap
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