buftools.py 文件源码

def __init__(self,
                 shape,
                 format=None,
                 strides=None,
                 readonly=None,
                 itemsize=None):
        if format is None:
            format = 'B'
        if readonly is None:
            readonly = False
        prefix = ''
        typecode = ''
        i = 0
        if i < len(format):
            try:
                prefix = self.prefixes[format[i]]
                i += 1
            except LookupError:
                pass
        if i < len(format) and format[i] == '1':
            i += 1
        if i == len(format) - 1:
            typecode = format[i]
        if itemsize is None:
            try:
                itemsize = ctypes.sizeof(self.types[prefix + typecode])
            except KeyError:
                raise ValueError("Unknown item format '" + format + "'")
        self.readonly = bool(readonly)
        self.format = format
        self._format = ctypes.create_string_buffer(format.encode('latin_1'))
        self.ndim = len(shape)
        self.itemsize = itemsize
        self.len = reduce(operator.mul, shape, 1) * self.itemsize
        self.shape = tuple(shape)
        self._shape = (ctypes.c_ssize_t * self.ndim)(*self.shape)
        if strides is None:
            self._strides = (ctypes.c_ssize_t * self.ndim)()
            self._strides[self.ndim - 1] = itemsize
            for i in range(self.ndim - 1, 0, -1):
                self._strides[i - 1] = self.shape[i] * self._strides[i]
            self.strides = tuple(self._strides)
        elif len(strides) == self.ndim:
            self.strides = tuple(strides)
            self._strides = (ctypes.c_ssize_t * self.ndim)(*self.strides)
        else:
            raise ValueError("Mismatch in length of strides and shape")
        buflen =  max(d * abs(s) for d, s in zip(self.shape, self.strides))
        self.buflen = buflen
        self._buf = (ctypes.c_ubyte * buflen)()
        offset = sum((d - 1) * abs(s)
                     for d, s in zip(self.shape, self.strides) if s < 0)
        self.buf = ctypes.addressof(self._buf) + offset