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/*
pybind11/buffer_info.h: Python buffer object interface
Copyright (c) 2016 Wenzel Jakob <wenzel.jakob@epfl.ch>
All rights reserved. Use of this source code is governed by a
BSD-style license that can be found in the LICENSE file.
*/
#pragma once
#include "detail/common.h"
PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
PYBIND11_NAMESPACE_BEGIN(detail)
// Default, C-style strides
inline std::vector<ssize_t> c_strides(const std::vector<ssize_t> &shape, ssize_t itemsize) {
auto ndim = shape.size();
std::vector<ssize_t> strides(ndim, itemsize);
if (ndim > 0) {
for (size_t i = ndim - 1; i > 0; --i) {
strides[i - 1] = strides[i] * shape[i];
}
}
return strides;
}
// F-style strides; default when constructing an array_t with `ExtraFlags & f_style`
inline std::vector<ssize_t> f_strides(const std::vector<ssize_t> &shape, ssize_t itemsize) {
auto ndim = shape.size();
std::vector<ssize_t> strides(ndim, itemsize);
for (size_t i = 1; i < ndim; ++i) {
strides[i] = strides[i - 1] * shape[i - 1];
}
return strides;
}
template <typename T, typename SFINAE = void>
struct compare_buffer_info;
PYBIND11_NAMESPACE_END(detail)
/// Information record describing a Python buffer object
struct buffer_info {
void *ptr = nullptr; // Pointer to the underlying storage
ssize_t itemsize = 0; // Size of individual items in bytes
ssize_t size = 0; // Total number of entries
std::string format; // For homogeneous buffers, this should be set to
// format_descriptor<T>::format()
ssize_t ndim = 0; // Number of dimensions
std::vector<ssize_t> shape; // Shape of the tensor (1 entry per dimension)
std::vector<ssize_t> strides; // Number of bytes between adjacent entries
// (for each per dimension)
bool readonly = false; // flag to indicate if the underlying storage may be written to
buffer_info() = default;
buffer_info(void *ptr,
ssize_t itemsize,
const std::string &format,
ssize_t ndim,
detail::any_container<ssize_t> shape_in,
detail::any_container<ssize_t> strides_in,
bool readonly = false)
: ptr(ptr), itemsize(itemsize), size(1), format(format), ndim(ndim),
shape(std::move(shape_in)), strides(std::move(strides_in)), readonly(readonly) {
if (ndim != (ssize_t) shape.size() || ndim != (ssize_t) strides.size()) {
pybind11_fail("buffer_info: ndim doesn't match shape and/or strides length");
}
for (size_t i = 0; i < (size_t) ndim; ++i) {
size *= shape[i];
}
}
template <typename T>
buffer_info(T *ptr,
detail::any_container<ssize_t> shape_in,
detail::any_container<ssize_t> strides_in,
bool readonly = false)
: buffer_info(private_ctr_tag(),
ptr,
sizeof(T),
format_descriptor<T>::format(),
static_cast<ssize_t>(shape_in->size()),
std::move(shape_in),
std::move(strides_in),
readonly) {}
buffer_info(void *ptr,
ssize_t itemsize,
const std::string &format,
ssize_t size,
bool readonly = false)
: buffer_info(ptr, itemsize, format, 1, {size}, {itemsize}, readonly) {}
template <typename T>
buffer_info(T *ptr, ssize_t size, bool readonly = false)
: buffer_info(ptr, sizeof(T), format_descriptor<T>::format(), size, readonly) {}
template <typename T>
buffer_info(const T *ptr, ssize_t size, bool readonly = true)
: buffer_info(
const_cast<T *>(ptr), sizeof(T), format_descriptor<T>::format(), size, readonly) {}
explicit buffer_info(Py_buffer *view, bool ownview = true)
: buffer_info(
view->buf,
view->itemsize,
view->format,
view->ndim,
{view->shape, view->shape + view->ndim},
/* Though buffer::request() requests PyBUF_STRIDES, ctypes objects
* ignore this flag and return a view with NULL strides.
* When strides are NULL, build them manually. */
view->strides
? std::vector<ssize_t>(view->strides, view->strides + view->ndim)
: detail::c_strides({view->shape, view->shape + view->ndim}, view->itemsize),
(view->readonly != 0)) {
// NOLINTNEXTLINE(cppcoreguidelines-prefer-member-initializer)
this->m_view = view;
// NOLINTNEXTLINE(cppcoreguidelines-prefer-member-initializer)
this->ownview = ownview;
}
buffer_info(const buffer_info &) = delete;
buffer_info &operator=(const buffer_info &) = delete;
buffer_info(buffer_info &&other) noexcept { (*this) = std::move(other); }
buffer_info &operator=(buffer_info &&rhs) noexcept {
ptr = rhs.ptr;
itemsize = rhs.itemsize;
size = rhs.size;
format = std::move(rhs.format);
ndim = rhs.ndim;
shape = std::move(rhs.shape);
strides = std::move(rhs.strides);
std::swap(m_view, rhs.m_view);
std::swap(ownview, rhs.ownview);
readonly = rhs.readonly;
return *this;
}
~buffer_info() {
if (m_view && ownview) {
PyBuffer_Release(m_view);
delete m_view;
}
}
Py_buffer *view() const { return m_view; }
Py_buffer *&view() { return m_view; }
/* True if the buffer item type is equivalent to `T`. */
// To define "equivalent" by example:
// `buffer_info::item_type_is_equivalent_to<int>(b)` and
// `buffer_info::item_type_is_equivalent_to<long>(b)` may both be true
// on some platforms, but `int` and `unsigned` will never be equivalent.
// For the ground truth, please inspect `detail::compare_buffer_info<>`.
template <typename T>
bool item_type_is_equivalent_to() const {
return detail::compare_buffer_info<T>::compare(*this);
}
private:
struct private_ctr_tag {};
buffer_info(private_ctr_tag,
void *ptr,
ssize_t itemsize,
const std::string &format,
ssize_t ndim,
detail::any_container<ssize_t> &&shape_in,
detail::any_container<ssize_t> &&strides_in,
bool readonly)
: buffer_info(
ptr, itemsize, format, ndim, std::move(shape_in), std::move(strides_in), readonly) {}
Py_buffer *m_view = nullptr;
bool ownview = false;
};
PYBIND11_NAMESPACE_BEGIN(detail)
template <typename T, typename SFINAE>
struct compare_buffer_info {
static bool compare(const buffer_info &b) {
// NOLINTNEXTLINE(bugprone-sizeof-expression) Needed for `PyObject *`
return b.format == format_descriptor<T>::format() && b.itemsize == (ssize_t) sizeof(T);
}
};
template <typename T>
struct compare_buffer_info<T, detail::enable_if_t<std::is_integral<T>::value>> {
static bool compare(const buffer_info &b) {
return (size_t) b.itemsize == sizeof(T)
&& (b.format == format_descriptor<T>::value
|| ((sizeof(T) == sizeof(long))
&& b.format == (std::is_unsigned<T>::value ? "L" : "l"))
|| ((sizeof(T) == sizeof(size_t))
&& b.format == (std::is_unsigned<T>::value ? "N" : "n")));
}
};
PYBIND11_NAMESPACE_END(detail)
PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
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