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<!DOCTYPE html>

<head>

<title>Buffer Protocol — Python 3.11.5 belgelendirmesi</title><meta name="viewport" content="width=device-width, initial-scale=1.0">

title="Python 3.11.5 belgelendirmesi içinde ara"

href="../_static/opensearch.xml"/>

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<h3><a href="../contents.html">İçindekiler</a></h3>

<ul>

<li><a class="reference internal" href="#">Buffer Protocol</a><ul>

<li><a class="reference internal" href="#buffer-structure">Buffer structure</a></li>

<li><a class="reference internal" href="#buffer-request-types">Buffer request types</a><ul>

<li><a class="reference internal" href="#request-independent-fields">request-independent fields</a></li>

<li><a class="reference internal" href="#readonly-format">readonly, format</a></li>

<li><a class="reference internal" href="#shape-strides-suboffsets">shape, strides, suboffsets</a></li>

<li><a class="reference internal" href="#contiguity-requests">contiguity requests</a></li>

<li><a class="reference internal" href="#compound-requests">compound requests</a></li>

</ul>

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<li><a class="reference internal" href="#complex-arrays">Complex arrays</a><ul>

<li><a class="reference internal" href="#numpy-style-shape-and-strides">NumPy-style: shape and strides</a></li>

<li><a class="reference internal" href="#pil-style-shape-strides-and-suboffsets">PIL-style: shape, strides and suboffsets</a></li>

</ul>

</li>

<li><a class="reference internal" href="#buffer-related-functions">Buffer-related functions</a></li>

</ul>

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<h4>Önceki konu</h4>

<a href="iter.html"

title="önceki bölüm">Iterator Protocol</a>

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<h4>Sonraki konu</h4>

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title="sonraki bölüm">Old Buffer Protocol</a>

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<a href="https://github.com/python/cpython/blob/3.11/Doc/c-api/buffer.rst"

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<h1>Buffer Protocol<a class="headerlink" href="#buffer-protocol" title="Permalink to this heading">¶</a></h1>

Certain objects available in Python wrap access to an underlying memory

array or buffer. Such objects include the built-in <a class="reference internal" href="../library/stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate">bytes</code></a> and

<a class="reference internal" href="../library/stdtypes.html#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate">bytearray</code></a>, and some extension types like <a class="reference internal" href="../library/array.html#array.array" title="array.array"><code class="xref py py-class docutils literal notranslate">array.array</code></a>.

Third-party libraries may define their own types for special purposes, such

as image processing or numeric analysis.

While each of these types have their own semantics, they share the common

characteristic of being backed by a possibly large memory buffer. It is

then desirable, in some situations, to access that buffer directly and

without intermediate copying.

Python provides such a facility at the C level in the form of the <a class="reference internal" href="#bufferobjects">buffer

protocol</a>. This protocol has two sides:

<li>on the producer side, a type can export a “buffer interface” which allows

objects of that type to expose information about their underlying buffer.

This interface is described in the section <a class="reference internal" href="typeobj.html#buffer-structs">Buffer Object Structures</a>;</li>

<li>on the consumer side, several means are available to obtain a pointer to

the raw underlying data of an object (for example a method parameter).</li>

</ul>

Simple objects such as <a class="reference internal" href="../library/stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate">bytes</code></a> and <a class="reference internal" href="../library/stdtypes.html#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate">bytearray</code></a> expose their

underlying buffer in byte-oriented form. Other forms are possible; for example,

the elements exposed by an <a class="reference internal" href="../library/array.html#array.array" title="array.array"><code class="xref py py-class docutils literal notranslate">array.array</code></a> can be multi-byte values.

An example consumer of the buffer interface is the <a class="reference internal" href="../library/io.html#io.BufferedIOBase.write" title="io.BufferedIOBase.write"><code class="xref py py-meth docutils literal notranslate">write()</code></a>

method of file objects: any object that can export a series of bytes through

the buffer interface can be written to a file. While <code class="xref py py-meth docutils literal notranslate">write()</code> only

needs read-only access to the internal contents of the object passed to it,

other methods such as <a class="reference internal" href="../library/io.html#io.BufferedIOBase.readinto" title="io.BufferedIOBase.readinto"><code class="xref py py-meth docutils literal notranslate">readinto()</code></a> need write access

to the contents of their argument. The buffer interface allows objects to

selectively allow or reject exporting of read-write and read-only buffers.

There are two ways for a consumer of the buffer interface to acquire a buffer

over a target object:

<li>call <a class="reference internal" href="#c.PyObject_GetBuffer" title="PyObject_GetBuffer"><code class="xref c c-func docutils literal notranslate">PyObject_GetBuffer()</code></a> with the right parameters;</li>

<li>call <a class="reference internal" href="arg.html#c.PyArg_ParseTuple" title="PyArg_ParseTuple"><code class="xref c c-func docutils literal notranslate">PyArg_ParseTuple()</code></a> (or one of its siblings) with one of the

<code class="docutils literal notranslate">y*</code>, <code class="docutils literal notranslate">w*</code> or <code class="docutils literal notranslate">s*</code> <a class="reference internal" href="arg.html#arg-parsing">format codes</a>.</li>

</ul>

In both cases, <a class="reference internal" href="#c.PyBuffer_Release" title="PyBuffer_Release"><code class="xref c c-func docutils literal notranslate">PyBuffer_Release()</code></a> must be called when the buffer

isn’t needed anymore. Failure to do so could lead to various issues such as

resource leaks.

<h2>Buffer structure<a class="headerlink" href="#buffer-structure" title="Permalink to this heading">¶</a></h2>

Buffer structures (or simply “buffers”) are useful as a way to expose the

binary data from another object to the Python programmer. They can also be

used as a zero-copy slicing mechanism. Using their ability to reference a

block of memory, it is possible to expose any data to the Python programmer

quite easily. The memory could be a large, constant array in a C extension,

it could be a raw block of memory for manipulation before passing to an

operating system library, or it could be used to pass around structured data

in its native, in-memory format.

Contrary to most data types exposed by the Python interpreter, buffers

are not <a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><code class="xref c c-type docutils literal notranslate">PyObject</code></a> pointers but rather simple C structures. This

allows them to be created and copied very simply. When a generic wrapper

around a buffer is needed, a <a class="reference internal" href="memoryview.html#memoryview-objects">memoryview</a> object

can be created.

For short instructions how to write an exporting object, see

<a class="reference internal" href="typeobj.html#buffer-structs">Buffer Object Structures</a>. For obtaining

a buffer, see <a class="reference internal" href="#c.PyObject_GetBuffer" title="PyObject_GetBuffer"><code class="xref c c-func docutils literal notranslate">PyObject_GetBuffer()</code></a>.

type Py_buffer<a class="headerlink" href="#c.Py_buffer" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

<dd> Part of the <a class="reference internal" href="stable.html#stable">Stable ABI</a> (including all members) since version 3.11.<dl class="c member">

void *buf<a class="headerlink" href="#c.Py_buffer.buf" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

<dd>A pointer to the start of the logical structure described by the buffer

fields. This can be any location within the underlying physical memory

block of the exporter. For example, with negative <a class="reference internal" href="#c.Py_buffer.strides" title="Py_buffer.strides"><code class="xref c c-member docutils literal notranslate">strides</code></a>

the value may point to the end of the memory block.

For <a class="reference internal" href="../glossary.html#term-contiguous">contiguous</a> arrays, the value points to the beginning of

the memory block.

</dd></dl>

<a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a> *obj<a class="headerlink" href="#c.Py_buffer.obj" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

<dd>A new reference to the exporting object. The reference is owned by

the consumer and automatically released

(i.e. reference count decremented)

and set to <code class="docutils literal notranslate">NULL</code> by

<a class="reference internal" href="#c.PyBuffer_Release" title="PyBuffer_Release"><code class="xref c c-func docutils literal notranslate">PyBuffer_Release()</code></a>. The field is the equivalent of the return

value of any standard C-API function.

As a special case, for temporary buffers that are wrapped by

<a class="reference internal" href="memoryview.html#c.PyMemoryView_FromBuffer" title="PyMemoryView_FromBuffer"><code class="xref c c-func docutils literal notranslate">PyMemoryView_FromBuffer()</code></a> or <a class="reference internal" href="#c.PyBuffer_FillInfo" title="PyBuffer_FillInfo"><code class="xref c c-func docutils literal notranslate">PyBuffer_FillInfo()</code></a>

this field is <code class="docutils literal notranslate">NULL</code>. In general, exporting objects MUST NOT

use this scheme.

</dd></dl>

<dd><code class="docutils literal notranslate">product(shape) * itemsize</code>. For contiguous arrays, this is the length

of the underlying memory block. For non-contiguous arrays, it is the length

that the logical structure would have if it were copied to a contiguous

representation.

Accessing <code class="docutils literal notranslate">((char *)buf)[0] up to ((char *)buf)[len-1]</code> is only valid

if the buffer has been obtained by a request that guarantees contiguity. In

most cases such a request will be <a class="reference internal" href="#c.PyBUF_SIMPLE" title="PyBUF_SIMPLE"><code class="xref c c-macro docutils literal notranslate">PyBUF_SIMPLE</code></a> or <a class="reference internal" href="#c.PyBUF_WRITABLE" title="PyBUF_WRITABLE"><code class="xref c c-macro docutils literal notranslate">PyBUF_WRITABLE</code></a>.

</dd></dl>

int readonly<a class="headerlink" href="#c.Py_buffer.readonly" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

<dd>An indicator of whether the buffer is read-only. This field is controlled

by the <a class="reference internal" href="#c.PyBUF_WRITABLE" title="PyBUF_WRITABLE"><code class="xref c c-macro docutils literal notranslate">PyBUF_WRITABLE</code></a> flag.

</dd></dl>

<dd>Item size in bytes of a single element. Same as the value of <a class="reference internal" href="../library/struct.html#struct.calcsize" title="struct.calcsize"><code class="xref py py-func docutils literal notranslate">struct.calcsize()</code></a>

called on non-<code class="docutils literal notranslate">NULL</code> <a class="reference internal" href="#c.Py_buffer.format" title="Py_buffer.format"><code class="xref c c-member docutils literal notranslate">format</code></a> values.

Important exception: If a consumer requests a buffer without the

<a class="reference internal" href="#c.PyBUF_FORMAT" title="PyBUF_FORMAT"><code class="xref c c-macro docutils literal notranslate">PyBUF_FORMAT</code></a> flag, <a class="reference internal" href="#c.Py_buffer.format" title="Py_buffer.format"><code class="xref c c-member docutils literal notranslate">format</code></a> will

be set to <code class="docutils literal notranslate">NULL</code>, but <a class="reference internal" href="#c.Py_buffer.itemsize" title="Py_buffer.itemsize"><code class="xref c c-member docutils literal notranslate">itemsize</code></a> still has

the value for the original format.

<code class="docutils literal notranslate">product(shape) * itemsize == len</code> still holds and the consumer

can use <a class="reference internal" href="#c.Py_buffer.itemsize" title="Py_buffer.itemsize"><code class="xref c c-member docutils literal notranslate">itemsize</code></a> to navigate the buffer.

If <a class="reference internal" href="#c.Py_buffer.shape" title="Py_buffer.shape"><code class="xref c c-member docutils literal notranslate">shape</code></a> is <code class="docutils literal notranslate">NULL</code> as a result of a <a class="reference internal" href="#c.PyBUF_SIMPLE" title="PyBUF_SIMPLE"><code class="xref c c-macro docutils literal notranslate">PyBUF_SIMPLE</code></a>

or a <a class="reference internal" href="#c.PyBUF_WRITABLE" title="PyBUF_WRITABLE"><code class="xref c c-macro docutils literal notranslate">PyBUF_WRITABLE</code></a> request, the consumer must disregard

<a class="reference internal" href="#c.Py_buffer.itemsize" title="Py_buffer.itemsize"><code class="xref c c-member docutils literal notranslate">itemsize</code></a> and assume <code class="docutils literal notranslate">itemsize == 1</code>.

</dd></dl>

const char *format<a class="headerlink" href="#c.Py_buffer.format" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

<dd>A NUL terminated string in <a class="reference internal" href="../library/struct.html#module-struct" title="struct: Interpret bytes as packed binary data."><code class="xref py py-mod docutils literal notranslate">struct</code></a> module style syntax describing

the contents of a single item. If this is <code class="docutils literal notranslate">NULL</code>, <code class="docutils literal notranslate">"B"</code> (unsigned bytes)

is assumed.

This field is controlled by the <a class="reference internal" href="#c.PyBUF_FORMAT" title="PyBUF_FORMAT"><code class="xref c c-macro docutils literal notranslate">PyBUF_FORMAT</code></a> flag.

</dd></dl>

int ndim<a class="headerlink" href="#c.Py_buffer.ndim" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

<dd>The number of dimensions the memory represents as an n-dimensional array.

If it is <code class="docutils literal notranslate">0</code>, <a class="reference internal" href="#c.Py_buffer.buf" title="Py_buffer.buf"><code class="xref c c-member docutils literal notranslate">buf</code></a> points to a single item representing

a scalar. In this case, <a class="reference internal" href="#c.Py_buffer.shape" title="Py_buffer.shape"><code class="xref c c-member docutils literal notranslate">shape</code></a>, <a class="reference internal" href="#c.Py_buffer.strides" title="Py_buffer.strides"><code class="xref c c-member docutils literal notranslate">strides</code></a>

and <a class="reference internal" href="#c.Py_buffer.suboffsets" title="Py_buffer.suboffsets"><code class="xref c c-member docutils literal notranslate">suboffsets</code></a> MUST be <code class="docutils literal notranslate">NULL</code>.

The maximum number of dimensions is given by <a class="reference internal" href="#c.PyBUF_MAX_NDIM" title="PyBUF_MAX_NDIM"><code class="xref c c-macro docutils literal notranslate">PyBUF_MAX_NDIM</code></a>.

</dd></dl>

<a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t">Py_ssize_t</a> *shape<a class="headerlink" href="#c.Py_buffer.shape" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

<dd>An array of <a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t"><code class="xref c c-type docutils literal notranslate">Py_ssize_t</code></a> of length <a class="reference internal" href="#c.Py_buffer.ndim" title="Py_buffer.ndim"><code class="xref c c-member docutils literal notranslate">ndim</code></a>

indicating the shape of the memory as an n-dimensional array. Note that

<code class="docutils literal notranslate">shape[0] * ... * shape[ndim-1] * itemsize</code> MUST be equal to

<a class="reference internal" href="#c.Py_buffer.len" title="Py_buffer.len"><code class="xref c c-member docutils literal notranslate">len</code></a>.

Shape values are restricted to <code class="docutils literal notranslate">shape[n] >= 0</code>. The case

<code class="docutils literal notranslate">shape[n] == 0</code> requires special attention. See <a class="reference internal" href="#complex-arrays">complex arrays</a>

for further information.

The shape array is read-only for the consumer.

</dd></dl>

<a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t">Py_ssize_t</a> *strides<a class="headerlink" href="#c.Py_buffer.strides" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

giving the number of bytes to skip to get to a new element in each

dimension.

Stride values can be any integer. For regular arrays, strides are

usually positive, but a consumer MUST be able to handle the case

<code class="docutils literal notranslate">strides[n] <= 0</code>. See <a class="reference internal" href="#complex-arrays">complex arrays</a> for further information.

The strides array is read-only for the consumer.

</dd></dl>

<a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t">Py_ssize_t</a> *suboffsets<a class="headerlink" href="#c.Py_buffer.suboffsets" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

If <code class="docutils literal notranslate">suboffsets[n] >= 0</code>, the values stored along the nth dimension are

pointers and the suboffset value dictates how many bytes to add to each

pointer after de-referencing. A suboffset value that is negative

indicates that no de-referencing should occur (striding in a contiguous

memory block).

If all suboffsets are negative (i.e. no de-referencing is needed), then

this field must be <code class="docutils literal notranslate">NULL</code> (the default value).

This type of array representation is used by the Python Imaging Library

(PIL). See <a class="reference internal" href="#complex-arrays">complex arrays</a> for further information how to access elements

of such an array.

The suboffsets array is read-only for the consumer.

</dd></dl>

void *internal<a class="headerlink" href="#c.Py_buffer.internal" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

<dd>This is for use internally by the exporting object. For example, this

might be re-cast as an integer by the exporter and used to store flags

about whether or not the shape, strides, and suboffsets arrays must be

freed when the buffer is released. The consumer MUST NOT alter this

value.

</dd></dl>

Constants:

PyBUF_MAX_NDIM<a class="headerlink" href="#c.PyBUF_MAX_NDIM" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

<dd>The maximum number of dimensions the memory represents.

Exporters MUST respect this limit, consumers of multi-dimensional

buffers SHOULD be able to handle up to <code class="xref c c-macro docutils literal notranslate">PyBUF_MAX_NDIM</code> dimensions.

Currently set to 64.

</dd></dl>

</section>

<h2>Buffer request types<a class="headerlink" href="#buffer-request-types" title="Permalink to this heading">¶</a></h2>

Buffers are usually obtained by sending a buffer request to an exporting

object via <a class="reference internal" href="#c.PyObject_GetBuffer" title="PyObject_GetBuffer"><code class="xref c c-func docutils literal notranslate">PyObject_GetBuffer()</code></a>. Since the complexity of the logical

structure of the memory can vary drastically, the consumer uses the flags

argument to specify the exact buffer type it can handle.

All <a class="reference internal" href="#c.Py_buffer" title="Py_buffer"><code class="xref c c-type docutils literal notranslate">Py_buffer</code></a> fields are unambiguously defined by the request

type.

<h3>request-independent fields<a class="headerlink" href="#request-independent-fields" title="Permalink to this heading">¶</a></h3>

The following fields are not influenced by flags and must always be filled in

with the correct values: <a class="reference internal" href="#c.Py_buffer.obj" title="Py_buffer.obj"><code class="xref c c-member docutils literal notranslate">obj</code></a>, <a class="reference internal" href="#c.Py_buffer.buf" title="Py_buffer.buf"><code class="xref c c-member docutils literal notranslate">buf</code></a>,

<a class="reference internal" href="#c.Py_buffer.len" title="Py_buffer.len"><code class="xref c c-member docutils literal notranslate">len</code></a>, <a class="reference internal" href="#c.Py_buffer.itemsize" title="Py_buffer.itemsize"><code class="xref c c-member docutils literal notranslate">itemsize</code></a>, <a class="reference internal" href="#c.Py_buffer.ndim" title="Py_buffer.ndim"><code class="xref c c-member docutils literal notranslate">ndim</code></a>.

</section>

<h3>readonly, format<a class="headerlink" href="#readonly-format" title="Permalink to this heading">¶</a></h3>

PyBUF_WRITABLE<a class="headerlink" href="#c.PyBUF_WRITABLE" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

<dd>Controls the <a class="reference internal" href="#c.Py_buffer.readonly" title="Py_buffer.readonly"><code class="xref c c-member docutils literal notranslate">readonly</code></a> field. If set, the exporter

MUST provide a writable buffer or else report failure. Otherwise, the

exporter MAY provide either a read-only or writable buffer, but the choice

MUST be consistent for all consumers.

</dd></dl>

PyBUF_FORMAT<a class="headerlink" href="#c.PyBUF_FORMAT" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

<dd>Controls the <a class="reference internal" href="#c.Py_buffer.format" title="Py_buffer.format"><code class="xref c c-member docutils literal notranslate">format</code></a> field. If set, this field MUST

be filled in correctly. Otherwise, this field MUST be <code class="docutils literal notranslate">NULL</code>.

</dd></dl>

</div></blockquote>

<a class="reference internal" href="#c.PyBUF_WRITABLE" title="PyBUF_WRITABLE"><code class="xref c c-macro docutils literal notranslate">PyBUF_WRITABLE</code></a> can be |’d to any of the flags in the next section.

Since <a class="reference internal" href="#c.PyBUF_SIMPLE" title="PyBUF_SIMPLE"><code class="xref c c-macro docutils literal notranslate">PyBUF_SIMPLE</code></a> is defined as 0, <a class="reference internal" href="#c.PyBUF_WRITABLE" title="PyBUF_WRITABLE"><code class="xref c c-macro docutils literal notranslate">PyBUF_WRITABLE</code></a>

can be used as a stand-alone flag to request a simple writable buffer.

<a class="reference internal" href="#c.PyBUF_FORMAT" title="PyBUF_FORMAT"><code class="xref c c-macro docutils literal notranslate">PyBUF_FORMAT</code></a> can be |’d to any of the flags except <a class="reference internal" href="#c.PyBUF_SIMPLE" title="PyBUF_SIMPLE"><code class="xref c c-macro docutils literal notranslate">PyBUF_SIMPLE</code></a>.

The latter already implies format <code class="docutils literal notranslate">B</code> (unsigned bytes).

</section>

<h3>shape, strides, suboffsets<a class="headerlink" href="#shape-strides-suboffsets" title="Permalink to this heading">¶</a></h3>

The flags that control the logical structure of the memory are listed

in decreasing order of complexity. Note that each flag contains all bits

of the flags below it.

<thead>

<tr class="row-odd"><th class="head">Request</th>

<th class="head">shape</th>

<th class="head">strides</th>

<th class="head">suboffsets</th>

</tr>

</thead>

<tbody>

PyBUF_INDIRECT<a class="headerlink" href="#c.PyBUF_INDIRECT" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

</td>

<td>if needed</td>

</tr>

PyBUF_STRIDES<a class="headerlink" href="#c.PyBUF_STRIDES" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

</td>

</tr>

PyBUF_ND<a class="headerlink" href="#c.PyBUF_ND" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

</td>

</tr>

PyBUF_SIMPLE<a class="headerlink" href="#c.PyBUF_SIMPLE" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

</td>

</tr>

</tbody>

</table>

</section>

<h3>contiguity requests<a class="headerlink" href="#contiguity-requests" title="Permalink to this heading">¶</a></h3>

C or Fortran <a class="reference internal" href="../glossary.html#term-contiguous">contiguity</a> can be explicitly requested,

with and without stride information. Without stride information, the buffer

must be C-contiguous.

<thead>

<tr class="row-odd"><th class="head">Request</th>

<th class="head">shape</th>

<th class="head">strides</th>

<th class="head">suboffsets</th>

<th class="head">contig</th>

</tr>

</thead>

<tbody>

PyBUF_C_CONTIGUOUS<a class="headerlink" href="#c.PyBUF_C_CONTIGUOUS" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

</td>

</tr>

PyBUF_F_CONTIGUOUS<a class="headerlink" href="#c.PyBUF_F_CONTIGUOUS" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

</td>

</tr>

PyBUF_ANY_CONTIGUOUS<a class="headerlink" href="#c.PyBUF_ANY_CONTIGUOUS" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

</td>

</tr>

<tr class="row-odd"><td><a class="reference internal" href="#c.PyBUF_ND" title="PyBUF_ND"><code class="xref c c-macro docutils literal notranslate">PyBUF_ND</code></a></td>

</tr>

</tbody>

</table>

</section>

<h3>compound requests<a class="headerlink" href="#compound-requests" title="Permalink to this heading">¶</a></h3>

All possible requests are fully defined by some combination of the flags in

the previous section. For convenience, the buffer protocol provides frequently

used combinations as single flags.

In the following table U stands for undefined contiguity. The consumer would

have to call <a class="reference internal" href="#c.PyBuffer_IsContiguous" title="PyBuffer_IsContiguous"><code class="xref c c-func docutils literal notranslate">PyBuffer_IsContiguous()</code></a> to determine contiguity.

<thead>

<tr class="row-odd"><th class="head">Request</th>

<th class="head">shape</th>

<th class="head">strides</th>

<th class="head">suboffsets</th>

<th class="head">contig</th>

<th class="head">readonly</th>

<th class="head">format</th>

</tr>

</thead>

<tbody>

PyBUF_FULL<a class="headerlink" href="#c.PyBUF_FULL" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

</td>

<td>if needed</td>

</tr>

PyBUF_FULL_RO<a class="headerlink" href="#c.PyBUF_FULL_RO" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

</td>

<td>if needed</td>

</tr>

PyBUF_RECORDS<a class="headerlink" href="#c.PyBUF_RECORDS" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

</td>

</tr>

PyBUF_RECORDS_RO<a class="headerlink" href="#c.PyBUF_RECORDS_RO" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

</td>

</tr>

PyBUF_STRIDED<a class="headerlink" href="#c.PyBUF_STRIDED" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

</td>

</tr>

PyBUF_STRIDED_RO<a class="headerlink" href="#c.PyBUF_STRIDED_RO" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

</td>

</tr>

PyBUF_CONTIG<a class="headerlink" href="#c.PyBUF_CONTIG" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

</td>

</tr>

PyBUF_CONTIG_RO<a class="headerlink" href="#c.PyBUF_CONTIG_RO" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

</td>

</tr>

</tbody>

</table>

</section>

<h2>Complex arrays<a class="headerlink" href="#complex-arrays" title="Permalink to this heading">¶</a></h2>

<h3>NumPy-style: shape and strides<a class="headerlink" href="#numpy-style-shape-and-strides" title="Permalink to this heading">¶</a></h3>

The logical structure of NumPy-style arrays is defined by <a class="reference internal" href="#c.Py_buffer.itemsize" title="Py_buffer.itemsize"><code class="xref c c-member docutils literal notranslate">itemsize</code></a>,

<a class="reference internal" href="#c.Py_buffer.ndim" title="Py_buffer.ndim"><code class="xref c c-member docutils literal notranslate">ndim</code></a>, <a class="reference internal" href="#c.Py_buffer.shape" title="Py_buffer.shape"><code class="xref c c-member docutils literal notranslate">shape</code></a> and <a class="reference internal" href="#c.Py_buffer.strides" title="Py_buffer.strides"><code class="xref c c-member docutils literal notranslate">strides</code></a>.

If <code class="docutils literal notranslate">ndim == 0</code>, the memory location pointed to by <a class="reference internal" href="#c.Py_buffer.buf" title="Py_buffer.buf"><code class="xref c c-member docutils literal notranslate">buf</code></a> is

interpreted as a scalar of size <a class="reference internal" href="#c.Py_buffer.itemsize" title="Py_buffer.itemsize"><code class="xref c c-member docutils literal notranslate">itemsize</code></a>. In that case,

both <a class="reference internal" href="#c.Py_buffer.shape" title="Py_buffer.shape"><code class="xref c c-member docutils literal notranslate">shape</code></a> and <a class="reference internal" href="#c.Py_buffer.strides" title="Py_buffer.strides"><code class="xref c c-member docutils literal notranslate">strides</code></a> are <code class="docutils literal notranslate">NULL</code>.

If <a class="reference internal" href="#c.Py_buffer.strides" title="Py_buffer.strides"><code class="xref c c-member docutils literal notranslate">strides</code></a> is <code class="docutils literal notranslate">NULL</code>, the array is interpreted as

a standard n-dimensional C-array. Otherwise, the consumer must access an

n-dimensional array as follows:

<div class="highlight-c notranslate"><div class="highlight"><pre>ptr = (char *)buf + indices[0] * strides[0] + ... + indices[n-1] * strides[n-1];

item = *((typeof(item) *)ptr);

</pre></div>

</div>

As noted above, <a class="reference internal" href="#c.Py_buffer.buf" title="Py_buffer.buf"><code class="xref c c-member docutils literal notranslate">buf</code></a> can point to any location within

the actual memory block. An exporter can check the validity of a buffer with

this function:

<div class="highlight-python notranslate"><div class="highlight"><pre>def verify_structure(memlen, itemsize, ndim, shape, strides, offset):

"""Verify that the parameters represent a valid array within

the bounds of the allocated memory:

char *mem: start of the physical memory block

memlen: length of the physical memory block

offset: (char *)buf - mem

"""

if offset % itemsize:

return False

if offset < 0 or offset+itemsize > memlen:

return False

if any(v % itemsize for v in strides):

return False

if ndim <= 0:

return ndim == 0 and not shape and not strides

if 0 in shape:

return True

imin = sum(strides[j]*(shape[j]-1) for j in range(ndim)

if strides[j] <= 0)

imax = sum(strides[j]*(shape[j]-1) for j in range(ndim)

if strides[j] > 0)

return 0 <= offset+imin and offset+imax+itemsize <= memlen

</pre></div>

</div>

</section>

<h3>PIL-style: shape, strides and suboffsets<a class="headerlink" href="#pil-style-shape-strides-and-suboffsets" title="Permalink to this heading">¶</a></h3>

In addition to the regular items, PIL-style arrays can contain pointers

that must be followed in order to get to the next element in a dimension.

For example, the regular three-dimensional C-array <code class="docutils literal notranslate">char v[2][2][3]</code> can

also be viewed as an array of 2 pointers to 2 two-dimensional arrays:

<code class="docutils literal notranslate">char (*v[2])[2][3]</code>. In suboffsets representation, those two pointers

can be embedded at the start of <a class="reference internal" href="#c.Py_buffer.buf" title="Py_buffer.buf"><code class="xref c c-member docutils literal notranslate">buf</code></a>, pointing

to two <code class="docutils literal notranslate">char x[2][3]</code> arrays that can be located anywhere in memory.

Here is a function that returns a pointer to the element in an N-D array

pointed to by an N-dimensional index when there are both non-<code class="docutils literal notranslate">NULL</code> strides

and suboffsets:

<div class="highlight-c notranslate"><div class="highlight"><pre>void *get_item_pointer(int ndim, void *buf, Py_ssize_t *strides,

Py_ssize_t *suboffsets, Py_ssize_t *indices) {

char *pointer = (char*)buf;

int i;

for (i = 0; i < ndim; i++) {

pointer += strides[i] * indices[i];

if (suboffsets[i] >=0 ) {

pointer = *((char**)pointer) + suboffsets[i];

}

return (void*)pointer;

}

</pre></div>

</div>

</section>

<h2>Buffer-related functions<a class="headerlink" href="#buffer-related-functions" title="Permalink to this heading">¶</a></h2>

int PyObject_CheckBuffer(<a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a> *obj)<a class="headerlink" href="#c.PyObject_CheckBuffer" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

<dd> Part of the <a class="reference internal" href="stable.html#stable">Stable ABI</a> since version 3.11.Return <code class="docutils literal notranslate">1</code> if obj supports the buffer interface otherwise <code class="docutils literal notranslate">0</code>. When <code class="docutils literal notranslate">1</code> is

returned, it doesn’t guarantee that <a class="reference internal" href="#c.PyObject_GetBuffer" title="PyObject_GetBuffer"><code class="xref c c-func docutils literal notranslate">PyObject_GetBuffer()</code></a> will

succeed. This function always succeeds.

</dd></dl>

int PyObject_GetBuffer(<a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a> *exporter, <a class="reference internal" href="#c.Py_buffer" title="Py_buffer">Py_buffer</a> *view, int flags)<a class="headerlink" href="#c.PyObject_GetBuffer" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

If the exporter cannot provide a buffer of the exact type, it MUST raise

<a class="reference internal" href="../library/exceptions.html#BufferError" title="BufferError"><code class="xref py py-exc docutils literal notranslate">BufferError</code></a>, set <code class="docutils literal notranslate">view->obj</code> to <code class="docutils literal notranslate">NULL</code> and

return <code class="docutils literal notranslate">-1</code>.

On success, fill in view, set <code class="docutils literal notranslate">view->obj</code> to a new reference

to exporter and return 0. In the case of chained buffer providers

that redirect requests to a single object, <code class="docutils literal notranslate">view->obj</code> MAY

refer to this object instead of exporter (See <a class="reference internal" href="typeobj.html#buffer-structs">Buffer Object Structures</a>).

Successful calls to <a class="reference internal" href="#c.PyObject_GetBuffer" title="PyObject_GetBuffer"><code class="xref c c-func docutils literal notranslate">PyObject_GetBuffer()</code></a> must be paired with calls

to <a class="reference internal" href="#c.PyBuffer_Release" title="PyBuffer_Release"><code class="xref c c-func docutils literal notranslate">PyBuffer_Release()</code></a>, similar to <code class="xref c c-func docutils literal notranslate">malloc()</code> and <code class="xref c c-func docutils literal notranslate">free()</code>.

Thus, after the consumer is done with the buffer, <a class="reference internal" href="#c.PyBuffer_Release" title="PyBuffer_Release"><code class="xref c c-func docutils literal notranslate">PyBuffer_Release()</code></a>

must be called exactly once.

</dd></dl>

void PyBuffer_Release(<a class="reference internal" href="#c.Py_buffer" title="Py_buffer">Py_buffer</a> *view)<a class="headerlink" href="#c.PyBuffer_Release" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

<dd> Part of the <a class="reference internal" href="stable.html#stable">Stable ABI</a> since version 3.11.Release the buffer view and release the <a class="reference internal" href="../glossary.html#term-strong-reference">strong reference</a>

(i.e. decrement the reference count) to the view’s supporting object,

<code class="docutils literal notranslate">view->obj</code>. This function MUST be called when the buffer

is no longer being used, otherwise reference leaks may occur.

It is an error to call this function on a buffer that was not obtained via

<a class="reference internal" href="#c.PyObject_GetBuffer" title="PyObject_GetBuffer"><code class="xref c c-func docutils literal notranslate">PyObject_GetBuffer()</code></a>.

</dd></dl>

<a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t">Py_ssize_t</a> PyBuffer_SizeFromFormat(const char *format)<a class="headerlink" href="#c.PyBuffer_SizeFromFormat" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

<dd> Part of the <a class="reference internal" href="stable.html#stable">Stable ABI</a> since version 3.11.Return the implied <a class="reference internal" href="#c.Py_buffer.itemsize" title="Py_buffer.itemsize"><code class="xref c c-member docutils literal notranslate">itemsize</code></a> from <a class="reference internal" href="#c.Py_buffer.format" title="Py_buffer.format"><code class="xref c c-member docutils literal notranslate">format</code></a>.

On error, raise an exception and return -1.

3.9 sürümünde geldi.

</div>

</dd></dl>

int PyBuffer_IsContiguous(const <a class="reference internal" href="#c.Py_buffer" title="Py_buffer">Py_buffer</a> *view, char order)<a class="headerlink" href="#c.PyBuffer_IsContiguous" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

<dd> Part of the <a class="reference internal" href="stable.html#stable">Stable ABI</a> since version 3.11.Return <code class="docutils literal notranslate">1</code> if the memory defined by the view is C-style (order is

<code class="docutils literal notranslate">'C'</code>) or Fortran-style (order is <code class="docutils literal notranslate">'F'</code>) <a class="reference internal" href="../glossary.html#term-contiguous">contiguous</a> or either one

(order is <code class="docutils literal notranslate">'A'</code>). Return <code class="docutils literal notranslate">0</code> otherwise. This function always succeeds.

</dd></dl>

void *PyBuffer_GetPointer(const <a class="reference internal" href="#c.Py_buffer" title="Py_buffer">Py_buffer</a> *view, const <a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t">Py_ssize_t</a> *indices)<a class="headerlink" href="#c.PyBuffer_GetPointer" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

indices must point to an array of <code class="docutils literal notranslate">view->ndim</code> indices.

</dd></dl>

int PyBuffer_FromContiguous(const <a class="reference internal" href="#c.Py_buffer" title="Py_buffer">Py_buffer</a> *view, const void *buf, <a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t">Py_ssize_t</a> len, char fort)<a class="headerlink" href="#c.PyBuffer_FromContiguous" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

fort can be <code class="docutils literal notranslate">'C'</code> or <code class="docutils literal notranslate">'F'</code> (for C-style or Fortran-style ordering).

<code class="docutils literal notranslate">0</code> is returned on success, <code class="docutils literal notranslate">-1</code> on error.

</dd></dl>

int PyBuffer_ToContiguous(void *buf, const <a class="reference internal" href="#c.Py_buffer" title="Py_buffer">Py_buffer</a> *src, <a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t">Py_ssize_t</a> len, char order)<a class="headerlink" href="#c.PyBuffer_ToContiguous" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

order can be <code class="docutils literal notranslate">'C'</code> or <code class="docutils literal notranslate">'F'</code> or <code class="docutils literal notranslate">'A'</code> (for C-style or Fortran-style

ordering or either one). <code class="docutils literal notranslate">0</code> is returned on success, <code class="docutils literal notranslate">-1</code> on error.

This function fails if len != src->len.

</dd></dl>

int PyObject_CopyData(<a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a> *dest, <a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a> *src)<a class="headerlink" href="#c.PyObject_CopyData" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

or Fortran-style buffers.

<code class="docutils literal notranslate">0</code> is returned on success, <code class="docutils literal notranslate">-1</code> on error.

</dd></dl>

void PyBuffer_FillContiguousStrides(int ndims, <a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t">Py_ssize_t</a> *shape, <a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t">Py_ssize_t</a> *strides, int itemsize, char order)<a class="headerlink" href="#c.PyBuffer_FillContiguousStrides" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

<dd> Part of the <a class="reference internal" href="stable.html#stable">Stable ABI</a> since version 3.11.Fill the strides array with byte-strides of a <a class="reference internal" href="../glossary.html#term-contiguous">contiguous</a> (C-style if

order is <code class="docutils literal notranslate">'C'</code> or Fortran-style if order is <code class="docutils literal notranslate">'F'</code>) array of the

given shape with the given number of bytes per element.

</dd></dl>

int PyBuffer_FillInfo(<a class="reference internal" href="#c.Py_buffer" title="Py_buffer">Py_buffer</a> *view, <a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a> *exporter, void *buf, <a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t">Py_ssize_t</a> len, int readonly, int flags)<a class="headerlink" href="#c.PyBuffer_FillInfo" title="Bu tanım için kalıcı bağlantı">¶</a> </dt>

with writability set according to readonly. buf is interpreted as a sequence

of unsigned bytes.

The flags argument indicates the request type. This function always fills in

view as specified by flags, unless buf has been designated as read-only

and <a class="reference internal" href="#c.PyBUF_WRITABLE" title="PyBUF_WRITABLE"><code class="xref c c-macro docutils literal notranslate">PyBUF_WRITABLE</code></a> is set in flags.

On success, set <code class="docutils literal notranslate">view->obj</code> to a new reference to exporter and

return 0. Otherwise, raise <a class="reference internal" href="../library/exceptions.html#BufferError" title="BufferError"><code class="xref py py-exc docutils literal notranslate">BufferError</code></a>, set

<code class="docutils literal notranslate">view->obj</code> to <code class="docutils literal notranslate">NULL</code> and return <code class="docutils literal notranslate">-1</code>;

If this function is used as part of a <a class="reference internal" href="typeobj.html#buffer-structs">getbufferproc</a>,

exporter MUST be set to the exporting object and flags must be passed

unmodified. Otherwise, exporter MUST be <code class="docutils literal notranslate">NULL</code>.