1 /*
2 pybind11/buffer_info.h: Python buffer object interface
3
4 Copyright (c) 2016 Wenzel Jakob <wenzel.jakob@epfl.ch>
5
6 All rights reserved. Use of this source code is governed by a
7 BSD-style license that can be found in the LICENSE file.
8 */
9
10 #pragma once
11
12 #include "detail/common.h"
13
14 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
15
PYBIND11_NAMESPACE_BEGIN(detail)16 PYBIND11_NAMESPACE_BEGIN(detail)
17
18 // Default, C-style strides
19 inline std::vector<ssize_t> c_strides(const std::vector<ssize_t> &shape, ssize_t itemsize) {
20 auto ndim = shape.size();
21 std::vector<ssize_t> strides(ndim, itemsize);
22 if (ndim > 0)
23 for (size_t i = ndim - 1; i > 0; --i)
24 strides[i - 1] = strides[i] * shape[i];
25 return strides;
26 }
27
28 // F-style strides; default when constructing an array_t with `ExtraFlags & f_style`
f_strides(const std::vector<ssize_t> & shape,ssize_t itemsize)29 inline std::vector<ssize_t> f_strides(const std::vector<ssize_t> &shape, ssize_t itemsize) {
30 auto ndim = shape.size();
31 std::vector<ssize_t> strides(ndim, itemsize);
32 for (size_t i = 1; i < ndim; ++i)
33 strides[i] = strides[i - 1] * shape[i - 1];
34 return strides;
35 }
36
37 PYBIND11_NAMESPACE_END(detail)
38
39 /// Information record describing a Python buffer object
40 struct buffer_info {
41 void *ptr = nullptr; // Pointer to the underlying storage
42 ssize_t itemsize = 0; // Size of individual items in bytes
43 ssize_t size = 0; // Total number of entries
44 std::string format; // For homogeneous buffers, this should be set to format_descriptor<T>::format()
45 ssize_t ndim = 0; // Number of dimensions
46 std::vector<ssize_t> shape; // Shape of the tensor (1 entry per dimension)
47 std::vector<ssize_t> strides; // Number of bytes between adjacent entries (for each per dimension)
48 bool readonly = false; // flag to indicate if the underlying storage may be written to
49
50 buffer_info() = default;
51
52 buffer_info(void *ptr, ssize_t itemsize, const std::string &format, ssize_t ndim,
53 detail::any_container<ssize_t> shape_in, detail::any_container<ssize_t> strides_in, bool readonly=false)
ptrbuffer_info54 : ptr(ptr), itemsize(itemsize), size(1), format(format), ndim(ndim),
55 shape(std::move(shape_in)), strides(std::move(strides_in)), readonly(readonly) {
56 if (ndim != (ssize_t) shape.size() || ndim != (ssize_t) strides.size())
57 pybind11_fail("buffer_info: ndim doesn't match shape and/or strides length");
58 for (size_t i = 0; i < (size_t) ndim; ++i)
59 size *= shape[i];
60 }
61
62 template <typename T>
63 buffer_info(T *ptr, detail::any_container<ssize_t> shape_in, detail::any_container<ssize_t> strides_in, bool readonly=false)
private_ctr_tagbuffer_info64 : 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) { }
65
66 buffer_info(void *ptr, ssize_t itemsize, const std::string &format, ssize_t size, bool readonly=false)
67 : buffer_info(ptr, itemsize, format, 1, {size}, {itemsize}, readonly) { }
68
69 template <typename T>
70 buffer_info(T *ptr, ssize_t size, bool readonly=false)
buffer_infobuffer_info71 : buffer_info(ptr, sizeof(T), format_descriptor<T>::format(), size, readonly) { }
72
73 template <typename T>
74 buffer_info(const T *ptr, ssize_t size, bool readonly=true)
buffer_infobuffer_info75 : buffer_info(const_cast<T*>(ptr), sizeof(T), format_descriptor<T>::format(), size, readonly) { }
76
77 explicit buffer_info(Py_buffer *view, bool ownview = true)
78 : buffer_info(view->buf, view->itemsize, view->format, view->ndim,
79 {view->shape, view->shape + view->ndim},
80 /* Though buffer::request() requests PyBUF_STRIDES, ctypes objects
81 * ignore this flag and return a view with NULL strides.
82 * When strides are NULL, build them manually. */
83 view->strides
84 ? std::vector<ssize_t>(view->strides, view->strides + view->ndim)
85 : detail::c_strides({view->shape, view->shape + view->ndim}, view->itemsize),
86 (view->readonly != 0)) {
87 this->m_view = view;
88 this->ownview = ownview;
89 }
90
91 buffer_info(const buffer_info &) = delete;
92 buffer_info& operator=(const buffer_info &) = delete;
93
buffer_infobuffer_info94 buffer_info(buffer_info &&other) noexcept { (*this) = std::move(other); }
95
96 buffer_info &operator=(buffer_info &&rhs) noexcept {
97 ptr = rhs.ptr;
98 itemsize = rhs.itemsize;
99 size = rhs.size;
100 format = std::move(rhs.format);
101 ndim = rhs.ndim;
102 shape = std::move(rhs.shape);
103 strides = std::move(rhs.strides);
104 std::swap(m_view, rhs.m_view);
105 std::swap(ownview, rhs.ownview);
106 readonly = rhs.readonly;
107 return *this;
108 }
109
~buffer_infobuffer_info110 ~buffer_info() {
111 if (m_view && ownview) { PyBuffer_Release(m_view); delete m_view; }
112 }
113
viewbuffer_info114 Py_buffer *view() const { return m_view; }
viewbuffer_info115 Py_buffer *&view() { return m_view; }
116 private:
117 struct private_ctr_tag { };
118
buffer_infobuffer_info119 buffer_info(private_ctr_tag, void *ptr, ssize_t itemsize, const std::string &format, ssize_t ndim,
120 detail::any_container<ssize_t> &&shape_in, detail::any_container<ssize_t> &&strides_in, bool readonly)
121 : buffer_info(ptr, itemsize, format, ndim, std::move(shape_in), std::move(strides_in), readonly) { }
122
123 Py_buffer *m_view = nullptr;
124 bool ownview = false;
125 };
126
127 PYBIND11_NAMESPACE_BEGIN(detail)
128
129 template <typename T, typename SFINAE = void> struct compare_buffer_info {
comparecompare_buffer_info130 static bool compare(const buffer_info& b) {
131 return b.format == format_descriptor<T>::format() && b.itemsize == (ssize_t) sizeof(T);
132 }
133 };
134
135 template <typename T> struct compare_buffer_info<T, detail::enable_if_t<std::is_integral<T>::value>> {
136 static bool compare(const buffer_info& b) {
137 return (size_t) b.itemsize == sizeof(T) && (b.format == format_descriptor<T>::value ||
138 ((sizeof(T) == sizeof(long)) && b.format == (std::is_unsigned<T>::value ? "L" : "l")) ||
139 ((sizeof(T) == sizeof(size_t)) && b.format == (std::is_unsigned<T>::value ? "N" : "n")));
140 }
141 };
142
143 PYBIND11_NAMESPACE_END(detail)
144 PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
145