pybind/pybind11
1
0
Fork 0
mirror of https://github.com/pybind/pybind11.git synced 2026-05-24 23:07:00 +00:00
Code Issues Packages Projects Releases Wiki Activity

Fix buffer protocol implementation (#5407)

Browse Source 
* Fix buffer protocol implementation

According to the buffer protocol, `ndim` is a _required_ field [1], and
should always be set correctly. Additionally, `shape` should be set if
flags includes `PyBUF_ND` or higher [2]. The current implementation only
set those fields if flags was `PyBUF_STRIDES`.

[1] https://docs.python.org/3/c-api/buffer.html#request-independent-fields
[2] https://docs.python.org/3/c-api/buffer.html#shape-strides-suboffsets

* Apply suggestions from review

* Obey contiguity requests for buffer protocol

If a contiguous buffer is requested, and the underlying buffer isn't,
then that should raise. This matches NumPy behaviour if you do something
like:
```
struct.unpack_from('5d', np.arange(20.0)[::4])  # Raises for contiguity
```

Also, if a buffer is contiguous, then it can masquerade as a
less-complex buffer, either by dropping strides, or even pretending to
be 1D. This matches NumPy behaviour if you do something like:
```
a = np.full((3, 5), 30.0)
struct.unpack_from('15d', a)  # --> Produces 1D tuple from 2D buffer.
```

* Handle review comments

* Test buffer protocol against NumPy

* Also check PyBUF_FORMAT results
This commit is contained in:
Elliott Sales de Andrade
2024-11-05 13:14:24 -05:00
committed by GitHub
parent 75e48c5f95
commit bc041de0db
3 changed files with 382 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files

56
include/pybind11/detail/class.h
View File

@@ -601,8 +601,10 @@ extern "C" inline int pybind11_getbuffer(PyObject *obj, Py_buffer *view, int fla
set_error(PyExc_BufferError, "Writable buffer requested for readonly storage");
return -1;
}
// Fill in all the information, and then downgrade as requested by the caller, or raise an
// error if that's not possible.
view->obj = obj;
view->ndim = 1;
view->internal = info;
view->buf = info->ptr;
view->itemsize = info->itemsize;
@@ -610,15 +612,59 @@ extern "C" inline int pybind11_getbuffer(PyObject *obj, Py_buffer *view, int fla
for (auto s : info->shape) {
view->len *= s;
}
view->ndim = static_cast<int>(info->ndim);
view->shape = info->shape.data();
view->strides = info->strides.data();
view->readonly = static_cast<int>(info->readonly);
if ((flags & PyBUF_FORMAT) == PyBUF_FORMAT) {
view->format = const_cast<char *>(info->format.c_str());
}
if ((flags & PyBUF_STRIDES) == PyBUF_STRIDES) {
view->ndim = (int) info->ndim;
view->strides = info->strides.data();
view->shape = info->shape.data();
// Note, all contiguity flags imply PyBUF_STRIDES and lower.
if ((flags & PyBUF_C_CONTIGUOUS) == PyBUF_C_CONTIGUOUS) {
if (PyBuffer_IsContiguous(view, 'C') == 0) {
std::memset(view, 0, sizeof(Py_buffer));
delete info;
set_error(PyExc_BufferError,
"C-contiguous buffer requested for discontiguous storage");
return -1;
}
} else if ((flags & PyBUF_F_CONTIGUOUS) == PyBUF_F_CONTIGUOUS) {
if (PyBuffer_IsContiguous(view, 'F') == 0) {
std::memset(view, 0, sizeof(Py_buffer));
delete info;
set_error(PyExc_BufferError,
"Fortran-contiguous buffer requested for discontiguous storage");
return -1;
}
} else if ((flags & PyBUF_ANY_CONTIGUOUS) == PyBUF_ANY_CONTIGUOUS) {
if (PyBuffer_IsContiguous(view, 'A') == 0) {
std::memset(view, 0, sizeof(Py_buffer));
delete info;
set_error(PyExc_BufferError, "Contiguous buffer requested for discontiguous storage");
return -1;
}
} else if ((flags & PyBUF_STRIDES) != PyBUF_STRIDES) {
// If no strides are requested, the buffer must be C-contiguous.
// https://docs.python.org/3/c-api/buffer.html#contiguity-requests
if (PyBuffer_IsContiguous(view, 'C') == 0) {
std::memset(view, 0, sizeof(Py_buffer));
delete info;
set_error(PyExc_BufferError,
"C-contiguous buffer requested for discontiguous storage");
return -1;
}
view->strides = nullptr;
// Since this is a contiguous buffer, it can also pretend to be 1D.
if ((flags & PyBUF_ND) != PyBUF_ND) {
view->shape = nullptr;
view->ndim = 0;
}
}
Py_INCREF(view->obj);
return 0;
}