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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;
}
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) {
this->m_view = view;
this->ownview = ownview;
}
buffer_info(const buffer_info &) = delete;
buffer_info& operator=(const buffer_info &) = delete;
buffer_info(buffer_info &&other) {
(*this) = std::move(other);
}
buffer_info& operator=(buffer_info &&rhs) {
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; }
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 = void> struct compare_buffer_info {
static bool compare(const buffer_info& b) {
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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