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# distutils: language = c++
from cython.cimports.cpython import Py_buffer
from cython.cimports.libcpp.vector import vector
@cython.cclass
class Matrix:
ncols: cython.Py_ssize_t
shape: cython.Py_ssize_t[2]
strides: cython.Py_ssize_t[2]
v: vector[cython.float]
def __cinit__(self, ncols: cython.Py_ssize_t):
self.ncols = ncols
def add_row(self):
"""Adds a row, initially zero-filled."""
self.v.resize(self.v.size() + self.ncols)
def __getbuffer__(self, buffer: cython.pointer(Py_buffer), flags: cython.int):
itemsize: cython.Py_ssize_t = cython.sizeof(self.v[0])
self.shape[0] = self.v.size() // self.ncols
self.shape[1] = self.ncols
# Stride 1 is the distance, in bytes, between two items in a row;
# this is the distance between two adjacent items in the vector.
# Stride 0 is the distance between the first elements of adjacent rows.
self.strides[1] = cython.cast(cython.Py_ssize_t, (
cython.cast(cython.p_char, cython.address(self.v[1]))
- cython.cast(cython.p_char, cython.address(self.v[0]))
)
)
self.strides[0] = self.ncols * self.strides[1]
buffer.buf = cython.cast(cython.p_char, cython.address(self.v[0]))
buffer.format = 'f' # float
buffer.internal = cython.NULL # see References
buffer.itemsize = itemsize
buffer.len = self.v.size() * itemsize # product(shape) * itemsize
buffer.ndim = 2
buffer.obj = self
buffer.readonly = 0
buffer.shape = self.shape
buffer.strides = self.strides
buffer.suboffsets = cython.NULL # for pointer arrays only
def __releasebuffer__(self, buffer: cython.pointer(Py_buffer)):
pass
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