buffer_info.h revision 12391:ceeca8b41e4b 
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
14NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
15
16/// Information record describing a Python buffer object
17struct buffer_info {
18    void *ptr = nullptr;          // Pointer to the underlying storage
19    ssize_t itemsize = 0;         // Size of individual items in bytes
20    ssize_t size = 0;             // Total number of entries
21    std::string format;           // For homogeneous buffers, this should be set to format_descriptor<T>::format()
22    ssize_t ndim = 0;             // Number of dimensions
23    std::vector<ssize_t> shape;   // Shape of the tensor (1 entry per dimension)
24    std::vector<ssize_t> strides; // Number of entries between adjacent entries (for each per dimension)
25
26    buffer_info() { }
27
28    buffer_info(void *ptr, ssize_t itemsize, const std::string &format, ssize_t ndim,
29                detail::any_container<ssize_t> shape_in, detail::any_container<ssize_t> strides_in)
30    : ptr(ptr), itemsize(itemsize), size(1), format(format), ndim(ndim),
31      shape(std::move(shape_in)), strides(std::move(strides_in)) {
32        if (ndim != (ssize_t) shape.size() || ndim != (ssize_t) strides.size())
33            pybind11_fail("buffer_info: ndim doesn't match shape and/or strides length");
34        for (size_t i = 0; i < (size_t) ndim; ++i)
35            size *= shape[i];
36    }
37
38    template <typename T>
39    buffer_info(T *ptr, detail::any_container<ssize_t> shape_in, detail::any_container<ssize_t> strides_in)
40    : 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)) { }
41
42    buffer_info(void *ptr, ssize_t itemsize, const std::string &format, ssize_t size)
43    : buffer_info(ptr, itemsize, format, 1, {size}, {itemsize}) { }
44
45    template <typename T>
46    buffer_info(T *ptr, ssize_t size)
47    : buffer_info(ptr, sizeof(T), format_descriptor<T>::format(), size) { }
48
49    explicit buffer_info(Py_buffer *view, bool ownview = true)
50    : buffer_info(view->buf, view->itemsize, view->format, view->ndim,
51            {view->shape, view->shape + view->ndim}, {view->strides, view->strides + view->ndim}) {
52        this->view = view;
53        this->ownview = ownview;
54    }
55
56    buffer_info(const buffer_info &) = delete;
57    buffer_info& operator=(const buffer_info &) = delete;
58
59    buffer_info(buffer_info &&other) {
60        (*this) = std::move(other);
61    }
62
63    buffer_info& operator=(buffer_info &&rhs) {
64        ptr = rhs.ptr;
65        itemsize = rhs.itemsize;
66        size = rhs.size;
67        format = std::move(rhs.format);
68        ndim = rhs.ndim;
69        shape = std::move(rhs.shape);
70        strides = std::move(rhs.strides);
71        std::swap(view, rhs.view);
72        std::swap(ownview, rhs.ownview);
73        return *this;
74    }
75
76    ~buffer_info() {
77        if (view && ownview) { PyBuffer_Release(view); delete view; }
78    }
79
80private:
81    struct private_ctr_tag { };
82
83    buffer_info(private_ctr_tag, void *ptr, ssize_t itemsize, const std::string &format, ssize_t ndim,
84                detail::any_container<ssize_t> &&shape_in, detail::any_container<ssize_t> &&strides_in)
85    : buffer_info(ptr, itemsize, format, ndim, std::move(shape_in), std::move(strides_in)) { }
86
87    Py_buffer *view = nullptr;
88    bool ownview = false;
89};
90
91NAMESPACE_BEGIN(detail)
92
93template <typename T, typename SFINAE = void> struct compare_buffer_info {
94    static bool compare(const buffer_info& b) {
95        return b.format == format_descriptor<T>::format() && b.itemsize == (ssize_t) sizeof(T);
96    }
97};
98
99template <typename T> struct compare_buffer_info<T, detail::enable_if_t<std::is_integral<T>::value>> {
100    static bool compare(const buffer_info& b) {
101        return (size_t) b.itemsize == sizeof(T) && (b.format == format_descriptor<T>::value ||
102            ((sizeof(T) == sizeof(long)) && b.format == (std::is_unsigned<T>::value ? "L" : "l")) ||
103            ((sizeof(T) == sizeof(size_t)) && b.format == (std::is_unsigned<T>::value ? "N" : "n")));
104    }
105};
106
107NAMESPACE_END(detail)
108NAMESPACE_END(PYBIND11_NAMESPACE)
109