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surfice.py
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surfice.py
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import io
import struct
import gzip
import numpy as np
from .wrapstruct import LabeledWrapStruct
from .dataobj_images import DataobjImage
from .arrayproxy import ArrayProxy
header_dtd = [
('magic', 'S2'), # 0; 0x5a4d (little endian) == "MZ"
('attr', 'u2'), # 2; Attributes bitfield reporting stored data
('nface', 'u4'), # 4; Number of faces
('nvert', 'u4'), # 8; Number of vertices
('nskip', 'u4'), # 12; Number of bytes to skip (for future header extensions)
]
header_dtype = np.dtype(header_dtd)
class MZ3Header(LabeledWrapStruct):
template_dtype = header_dtype
compression = False
@classmethod
def from_header(klass, header=None, check=True):
if type(header) == klass:
obj = header.copy()
if check:
obj.check_fix()
return obj
def copy(self):
ret = super().copy()
ret.compression = self.compression
ret._nscalar = self._nscalar
return ret
@classmethod
def from_fileobj(klass, fileobj, endianness=None, check=True):
raw_str = fileobj.read(klass.template_dtype.itemsize)
compression = raw_str[:2] == b'\x1f\x8b'
if compression:
fileobj.seek(0)
with gzip.open(fileobj, 'rb') as fobj:
raw_str = fobj.read(klass.template_dtype.itemsize)
hdr = klass(raw_str, endianness, check)
hdr.compression = compression
hdr._nscalar = hdr._calculate_nscalar(fileobj)
return hdr
def get_data_offset(self):
_, attr, nface, nvert, nskip = self._structarr.tolist()
isface = attr & 1 != 0
isvert = attr & 2 != 0
isrgba = attr & 4 != 0
return 16 + nskip + isface * nface * 12 + isvert * nvert * 12 + isrgba * nvert * 12
def _calculate_nscalar(self, fileobj):
_, attr, nface, nvert, nskip = self._structarr.tolist()
isscalar = attr & 8 != 0
isdouble = attr & 16 != 0
base_size = self.get_data_offset()
nscalar = 0
if isscalar or isdouble:
factor = nvert * (4 if isscalar else 8)
ret = fileobj.tell()
if self.compression:
fileobj.seek(-4, 2)
full_size_mod_4gb = struct.unpack('I', fileobj.read(4))[0]
full_size = full_size_mod_4gb
nscalar, remainder = divmod(full_size - base_size, factor)
for _ in range(5):
full_size += (1 << 32)
nscalar, remainder = divmod(full_size - base_size, factor)
if remainder == 0:
break
else:
fileobj.seek(0)
with gzip.open(fileobj, 'rb') as fobj:
fobj.seek(0, 2)
full_size = fobj.tell()
nscalar, remainder = divmod(full_size - base_size, factor)
if remainder:
raise ValueError("Apparent file size failure")
else:
fileobj.seek(0, 2)
full_size = fileobj.tell()
nscalar, remainder = divmod(full_size - base_size, factor)
if remainder:
raise ValueError("Apparent file size failure")
fileobj.seek(ret)
return nscalar
@classmethod
def guessed_endian(klass, mapping):
return '<'
@classmethod
def default_structarr(klass, endianness=None):
if endianness is not None and endian_codes[endianness] != '<':
raise ValueError('MZ3Header must always be little endian')
structarr = super().default_structarr(endianness=endianness)
structarr['magic'] = b"MZ"
return structarr
@classmethod
def may_contain_header(klass, binaryblock):
if len(binaryblock) < 16:
return False
# May be gzipped without changing extension
if binaryblock[:2] == b'\x1f\x8b':
with gzip.open(io.BytesIO(binaryblock), 'rb') as fobj:
binaryblock = fobj.read(16)
hdr_struct = np.ndarray(shape=(), dtype=klass.template_dtype, buffer=binaryblock[:16])
return hdr_struct['magic'] == b'MZ'
def get_data_dtype(self):
if self._structarr['attr'] & 8:
return np.dtype('<f4')
elif self._structarr['attr'] & 16:
return np.dtype('<f8')
def set_data_dtype(self, datatype):
if np.dtype(datatype).byteorder == ">":
raise ValueError("Cannot set type to big-endian")
dt = np.dtype(datatype).newbyteorder("<")
if dt == np.dtype('<f8'):
self._structarr['attr'] |= 0b00010000
elif dt == np.dtype('<f4'):
self._structarr['attr'] &= 0b11101111
else:
raise ValueError(f"Cannot set dtype: {datatype}")
def get_data_shape(self):
base_shape = (int(self._structarr['nvert']),)
if self._nscalar == 0:
return ()
elif self._nscalar == 1:
return base_shape
else:
return base_shape + (self._nscalar,)
class MZ3Image(DataobjImage):
header_class = MZ3Header
valid_exts = ('.mz3',)
files_types = (('image', '.mz3'),)
ImageArrayProxy = ArrayProxy
@classmethod
def from_file_map(klass, file_map, *, mmap=True, keep_file_open=None):
if mmap not in (True, False, 'c', 'r'):
raise ValueError("mmap should be one of {True, False, 'c', 'r'}")
fh = file_map['image']
with fh.get_prepare_fileobj(mode='rb') as fileobj:
header = klass.header_class.from_fileobj(fileobj)
print(header)
data_dtype = header.get_data_dtype()
if data_dtype:
spec = (header.get_data_shape(), data_dtype, header.get_data_offset())
dataobj = klass.ImageArrayProxy(fh.filename, spec, mmap=mmap,
keep_file_open=keep_file_open,
compression="gz" if header.compression else None)
else:
dataobj = np.array((), dtype="<f4")
img = klass(dataobj, header=header)
return img