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

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

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

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

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

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

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

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

  106. </ul>

  107. </li>

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

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

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

  111. </ul>

  112. </li>

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

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  206.   <section id="buffer-protocol">

  207. <span id="bufferobjects"></span><span id="index-0"></span><h1>Buffer Protocol<a class="headerlink" href="#buffer-protocol" title="Link to this heading">¶</a></h1>

  208. <p>Certain objects available in Python wrap access to an underlying memory

  209. array or <em>buffer</em>.  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"><span class="pre">bytes</span></code></a> and

  210. <a class="reference internal" href="../library/stdtypes.html#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytearray</span></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"><span class="pre">array.array</span></code></a>.

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

  212. as image processing or numeric analysis.</p>

  213. <p>While each of these types have their own semantics, they share the common

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

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

  216. without intermediate copying.</p>

  217. <p>Python provides such a facility at the C level in the form of the <a class="reference internal" href="#bufferobjects"><span class="std std-ref">buffer

  218. protocol</span></a>.  This protocol has two sides:</p>

  219. <ul class="simple" id="index-1">

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

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

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

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

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

  225. </ul>

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

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

  228. 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"><span class="pre">array.array</span></code></a> can be multi-byte values.</p>

  229. <p>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"><span class="pre">write()</span></code></a>

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

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

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

  233. 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"><span class="pre">readinto()</span></code></a> need write access

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

  235. selectively allow or reject exporting of read-write and read-only buffers.</p>

  236. <p>There are two ways for a consumer of the buffer interface to acquire a buffer

  237. over a target object:</p>

  238. <ul class="simple">

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

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

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

  242. </ul>

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

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

  245. resource leaks.</p>

  246. <section id="buffer-structure">

  247. <span id="id1"></span><h2>Buffer structure<a class="headerlink" href="#buffer-structure" title="Link to this heading">¶</a></h2>

  248. <p>Buffer structures (or simply “buffers”) are useful as a way to expose the

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

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

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

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

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

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

  255. in its native, in-memory format.</p>

  256. <p>Contrary to most data types exposed by the Python interpreter, buffers

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

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

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

  260. can be created.</p>

  261. <p>For short instructions how to write an exporting object, see

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

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

  264. <dl class="c type">

  265. <dt class="sig sig-object c" id="c.Py_buffer">

  266. <span class="k"><span class="pre">type</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">Py_buffer</span></span></span><a class="headerlink" href="#c.Py_buffer" title="Link to this definition">¶</a><br /></dt>

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

  268. <dt class="sig sig-object c" id="c.Py_buffer.buf">

  269. <span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">buf</span></span></span><a class="headerlink" href="#c.Py_buffer.buf" title="Link to this definition">¶</a><br /></dt>

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

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

  272. 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"><span class="pre">strides</span></code></a>

  273. the value may point to the end of the memory block.</p>

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

  275. the memory block.</p>

  276. </dd></dl>

  277. 

  278. <dl class="c member">

  279. <dt class="sig sig-object c" id="c.Py_buffer.obj">

  280. <a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n"><span class="pre">PyObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">obj</span></span></span><a class="headerlink" href="#c.Py_buffer.obj" title="Link to this definition">¶</a><br /></dt>

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

  282. the consumer and automatically released

  283. (i.e. reference count decremented)

  284. and set to <code class="docutils literal notranslate"><span class="pre">NULL</span></code> by

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

  286. value of any standard C-API function.</p>

  287. <p>As a special case, for <em>temporary</em> buffers that are wrapped by

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

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

  290. use this scheme.</p>

  291. </dd></dl>

  292. 

  293. <dl class="c member">

  294. <dt class="sig sig-object c" id="c.Py_buffer.len">

  295. <a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t"><span class="n"><span class="pre">Py_ssize_t</span></span></a><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">len</span></span></span><a class="headerlink" href="#c.Py_buffer.len" title="Link to this definition">¶</a><br /></dt>

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

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

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

  299. representation.</p>

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

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

  302. 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"><span class="pre">PyBUF_SIMPLE</span></code></a> or <a class="reference internal" href="#c.PyBUF_WRITABLE" title="PyBUF_WRITABLE"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyBUF_WRITABLE</span></code></a>.</p>

  303. </dd></dl>

  304. 

  305. <dl class="c member">

  306. <dt class="sig sig-object c" id="c.Py_buffer.readonly">

  307. <span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">readonly</span></span></span><a class="headerlink" href="#c.Py_buffer.readonly" title="Link to this definition">¶</a><br /></dt>

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

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

  310. </dd></dl>

  311. 

  312. <dl class="c member">

  313. <dt class="sig sig-object c" id="c.Py_buffer.itemsize">

  314. <a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t"><span class="n"><span class="pre">Py_ssize_t</span></span></a><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">itemsize</span></span></span><a class="headerlink" href="#c.Py_buffer.itemsize" title="Link to this definition">¶</a><br /></dt>

  315. <dd><p>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"><span class="pre">struct.calcsize()</span></code></a>

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

  317. <p>Important exception: If a consumer requests a buffer without the

  318. <a class="reference internal" href="#c.PyBUF_FORMAT" title="PyBUF_FORMAT"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyBUF_FORMAT</span></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"><span class="pre">format</span></code></a> will

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

  320. the value for the original format.</p>

  321. <p>If <a class="reference internal" href="#c.Py_buffer.shape" title="Py_buffer.shape"><code class="xref c c-member docutils literal notranslate"><span class="pre">shape</span></code></a> is present, the equality

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

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

  324. <p>If <a class="reference internal" href="#c.Py_buffer.shape" title="Py_buffer.shape"><code class="xref c c-member docutils literal notranslate"><span class="pre">shape</span></code></a> is <code class="docutils literal notranslate"><span class="pre">NULL</span></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"><span class="pre">PyBUF_SIMPLE</span></code></a>

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

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

  327. </dd></dl>

  328. 

  329. <dl class="c member">

  330. <dt class="sig sig-object c" id="c.Py_buffer.format">

  331. <span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="kt"><span class="pre">char</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">format</span></span></span><a class="headerlink" href="#c.Py_buffer.format" title="Link to this definition">¶</a><br /></dt>

  332. <dd><p>A <em>NUL</em> 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"><span class="pre">struct</span></code></a> module style syntax describing

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

  334. is assumed.</p>

  335. <p>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"><span class="pre">PyBUF_FORMAT</span></code></a> flag.</p>

  336. </dd></dl>

  337. 

  338. <dl class="c member">

  339. <dt class="sig sig-object c" id="c.Py_buffer.ndim">

  340. <span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">ndim</span></span></span><a class="headerlink" href="#c.Py_buffer.ndim" title="Link to this definition">¶</a><br /></dt>

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

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

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

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

  345. 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"><span class="pre">PyBUF_MAX_NDIM</span></code></a>.</p>

  346. </dd></dl>

  347. 

  348. <dl class="c member">

  349. <dt class="sig sig-object c" id="c.Py_buffer.shape">

  350. <a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t"><span class="n"><span class="pre">Py_ssize_t</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">shape</span></span></span><a class="headerlink" href="#c.Py_buffer.shape" title="Link to this definition">¶</a><br /></dt>

  351. <dd><p>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"><span class="pre">Py_ssize_t</span></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"><span class="pre">ndim</span></code></a>

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

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

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

  355. <p>Shape values are restricted to <code class="docutils literal notranslate"><span class="pre">shape[n]</span> <span class="pre">&gt;=</span> <span class="pre">0</span></code>. The case

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

  357. for further information.</p>

  358. <p>The shape array is read-only for the consumer.</p>

  359. </dd></dl>

  360. 

  361. <dl class="c member">

  362. <dt class="sig sig-object c" id="c.Py_buffer.strides">

  363. <a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t"><span class="n"><span class="pre">Py_ssize_t</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">strides</span></span></span><a class="headerlink" href="#c.Py_buffer.strides" title="Link to this definition">¶</a><br /></dt>

  364. <dd><p>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"><span class="pre">Py_ssize_t</span></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"><span class="pre">ndim</span></code></a>

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

  366. dimension.</p>

  367. <p>Stride values can be any integer. For regular arrays, strides are

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

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

  370. <p>The strides array is read-only for the consumer.</p>

  371. </dd></dl>

  372. 

  373. <dl class="c member">

  374. <dt class="sig sig-object c" id="c.Py_buffer.suboffsets">

  375. <a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t"><span class="n"><span class="pre">Py_ssize_t</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">suboffsets</span></span></span><a class="headerlink" href="#c.Py_buffer.suboffsets" title="Link to this definition">¶</a><br /></dt>

  376. <dd><p>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"><span class="pre">Py_ssize_t</span></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"><span class="pre">ndim</span></code></a>.

  377. If <code class="docutils literal notranslate"><span class="pre">suboffsets[n]</span> <span class="pre">&gt;=</span> <span class="pre">0</span></code>, the values stored along the nth dimension are

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

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

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

  381. memory block).</p>

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

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

  384. <p>This type of array representation is used by the Python Imaging Library

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

  386. of such an array.</p>

  387. <p>The suboffsets array is read-only for the consumer.</p>

  388. </dd></dl>

  389. 

  390. <dl class="c member">

  391. <dt class="sig sig-object c" id="c.Py_buffer.internal">

  392. <span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">internal</span></span></span><a class="headerlink" href="#c.Py_buffer.internal" title="Link to this definition">¶</a><br /></dt>

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

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

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

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

  397. value.</p>

  398. </dd></dl>

  399. 

  400. </dd></dl>

  401. 

  402. <p>Constants:</p>

  403. <dl class="c macro">

  404. <dt class="sig sig-object c" id="c.PyBUF_MAX_NDIM">

  405. <span class="sig-name descname"><span class="n"><span class="pre">PyBUF_MAX_NDIM</span></span></span><a class="headerlink" href="#c.PyBUF_MAX_NDIM" title="Link to this definition">¶</a><br /></dt>

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

  407. Exporters MUST respect this limit, consumers of multi-dimensional

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

  409. Currently set to 64.</p>

  410. </dd></dl>

  411. 

  412. </section>

  413. <section id="buffer-request-types">

  414. <span id="id2"></span><h2>Buffer request types<a class="headerlink" href="#buffer-request-types" title="Link to this heading">¶</a></h2>

  415. <p>Buffers are usually obtained by sending a buffer request to an exporting

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

  417. structure of the memory can vary drastically, the consumer uses the <em>flags</em>

  418. argument to specify the exact buffer type it can handle.</p>

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

  420. type.</p>

  421. <section id="request-independent-fields">

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

  423. <p>The following fields are not influenced by <em>flags</em> and must always be filled in

  424. 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"><span class="pre">obj</span></code></a>, <a class="reference internal" href="#c.Py_buffer.buf" title="Py_buffer.buf"><code class="xref c c-member docutils literal notranslate"><span class="pre">buf</span></code></a>,

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

  426. </section>

  427. <section id="readonly-format">

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

  429. <blockquote>

  430. <div><dl class="c macro">

  431. <dt class="sig sig-object c" id="c.PyBUF_WRITABLE">

  432. <span class="sig-name descname"><span class="n"><span class="pre">PyBUF_WRITABLE</span></span></span><a class="headerlink" href="#c.PyBUF_WRITABLE" title="Link to this definition">¶</a><br /></dt>

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

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

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

  436. MUST be consistent for all consumers.</p>

  437. </dd></dl>

  438. 

  439. <dl class="c macro">

  440. <dt class="sig sig-object c" id="c.PyBUF_FORMAT">

  441. <span class="sig-name descname"><span class="n"><span class="pre">PyBUF_FORMAT</span></span></span><a class="headerlink" href="#c.PyBUF_FORMAT" title="Link to this definition">¶</a><br /></dt>

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

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

  444. </dd></dl>

  445. 

  446. </div></blockquote>

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

  448. Since <a class="reference internal" href="#c.PyBUF_SIMPLE" title="PyBUF_SIMPLE"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyBUF_SIMPLE</span></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"><span class="pre">PyBUF_WRITABLE</span></code></a>

  449. can be used as a stand-alone flag to request a simple writable buffer.</p>

  450. <p><a class="reference internal" href="#c.PyBUF_FORMAT" title="PyBUF_FORMAT"><code class="xref c c-macro docutils literal notranslate"><span class="pre">PyBUF_FORMAT</span></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"><span class="pre">PyBUF_SIMPLE</span></code></a>.

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

  452. </section>

  453. <section id="shape-strides-suboffsets">

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

  455. <p>The flags that control the logical structure of the memory are listed

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

  457. of the flags below it.</p>

  458. <table class="docutils align-default">

  459. <thead>

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

  461. <th class="head"><p>shape</p></th>

  462. <th class="head"><p>strides</p></th>

  463. <th class="head"><p>suboffsets</p></th>

  464. </tr>

  465. </thead>

  466. <tbody>

  467. <tr class="row-even"><td><dl class="c macro">

  468. <dt class="sig sig-object c" id="c.PyBUF_INDIRECT">

  469. <span class="sig-name descname"><span class="n"><span class="pre">PyBUF_INDIRECT</span></span></span><a class="headerlink" href="#c.PyBUF_INDIRECT" title="Link to this definition">¶</a><br /></dt>

  470. <dd></dd></dl>

  471. 

  472. </td>

  473. <td><p>yes</p></td>

  474. <td><p>yes</p></td>

  475. <td><p>if needed</p></td>

  476. </tr>

  477. <tr class="row-odd"><td><dl class="c macro">

  478. <dt class="sig sig-object c" id="c.PyBUF_STRIDES">

  479. <span class="sig-name descname"><span class="n"><span class="pre">PyBUF_STRIDES</span></span></span><a class="headerlink" href="#c.PyBUF_STRIDES" title="Link to this definition">¶</a><br /></dt>

  480. <dd></dd></dl>

  481. 

  482. </td>

  483. <td><p>yes</p></td>

  484. <td><p>yes</p></td>

  485. <td><p>NULL</p></td>

  486. </tr>

  487. <tr class="row-even"><td><dl class="c macro">

  488. <dt class="sig sig-object c" id="c.PyBUF_ND">

  489. <span class="sig-name descname"><span class="n"><span class="pre">PyBUF_ND</span></span></span><a class="headerlink" href="#c.PyBUF_ND" title="Link to this definition">¶</a><br /></dt>

  490. <dd></dd></dl>

  491. 

  492. </td>

  493. <td><p>yes</p></td>

  494. <td><p>NULL</p></td>

  495. <td><p>NULL</p></td>

  496. </tr>

  497. <tr class="row-odd"><td><dl class="c macro">

  498. <dt class="sig sig-object c" id="c.PyBUF_SIMPLE">

  499. <span class="sig-name descname"><span class="n"><span class="pre">PyBUF_SIMPLE</span></span></span><a class="headerlink" href="#c.PyBUF_SIMPLE" title="Link to this definition">¶</a><br /></dt>

  500. <dd></dd></dl>

  501. 

  502. </td>

  503. <td><p>NULL</p></td>

  504. <td><p>NULL</p></td>

  505. <td><p>NULL</p></td>

  506. </tr>

  507. </tbody>

  508. </table>

  509. </section>

  510. <section id="contiguity-requests">

  511. <span id="index-2"></span><h3>contiguity requests<a class="headerlink" href="#contiguity-requests" title="Link to this heading">¶</a></h3>

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

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

  514. must be C-contiguous.</p>

  515. <table class="docutils align-default">

  516. <thead>

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

  518. <th class="head"><p>shape</p></th>

  519. <th class="head"><p>strides</p></th>

  520. <th class="head"><p>suboffsets</p></th>

  521. <th class="head"><p>contig</p></th>

  522. </tr>

  523. </thead>

  524. <tbody>

  525. <tr class="row-even"><td><dl class="c macro">

  526. <dt class="sig sig-object c" id="c.PyBUF_C_CONTIGUOUS">

  527. <span class="sig-name descname"><span class="n"><span class="pre">PyBUF_C_CONTIGUOUS</span></span></span><a class="headerlink" href="#c.PyBUF_C_CONTIGUOUS" title="Link to this definition">¶</a><br /></dt>

  528. <dd></dd></dl>

  529. 

  530. </td>

  531. <td><p>yes</p></td>

  532. <td><p>yes</p></td>

  533. <td><p>NULL</p></td>

  534. <td><p>C</p></td>

  535. </tr>

  536. <tr class="row-odd"><td><dl class="c macro">

  537. <dt class="sig sig-object c" id="c.PyBUF_F_CONTIGUOUS">

  538. <span class="sig-name descname"><span class="n"><span class="pre">PyBUF_F_CONTIGUOUS</span></span></span><a class="headerlink" href="#c.PyBUF_F_CONTIGUOUS" title="Link to this definition">¶</a><br /></dt>

  539. <dd></dd></dl>

  540. 

  541. </td>

  542. <td><p>yes</p></td>

  543. <td><p>yes</p></td>

  544. <td><p>NULL</p></td>

  545. <td><p>F</p></td>

  546. </tr>

  547. <tr class="row-even"><td><dl class="c macro">

  548. <dt class="sig sig-object c" id="c.PyBUF_ANY_CONTIGUOUS">

  549. <span class="sig-name descname"><span class="n"><span class="pre">PyBUF_ANY_CONTIGUOUS</span></span></span><a class="headerlink" href="#c.PyBUF_ANY_CONTIGUOUS" title="Link to this definition">¶</a><br /></dt>

  550. <dd></dd></dl>

  551. 

  552. </td>

  553. <td><p>yes</p></td>

  554. <td><p>yes</p></td>

  555. <td><p>NULL</p></td>

  556. <td><p>C or F</p></td>

  557. </tr>

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

  559. <td><p>yes</p></td>

  560. <td><p>NULL</p></td>

  561. <td><p>NULL</p></td>

  562. <td><p>C</p></td>

  563. </tr>

  564. </tbody>

  565. </table>

  566. </section>

  567. <section id="compound-requests">

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

  569. <p>All possible requests are fully defined by some combination of the flags in

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

  571. used combinations as single flags.</p>

  572. <p>In the following table <em>U</em> stands for undefined contiguity. The consumer would

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

  574. <table class="docutils align-default">

  575. <thead>

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

  577. <th class="head"><p>shape</p></th>

  578. <th class="head"><p>strides</p></th>

  579. <th class="head"><p>suboffsets</p></th>

  580. <th class="head"><p>contig</p></th>

  581. <th class="head"><p>readonly</p></th>

  582. <th class="head"><p>format</p></th>

  583. </tr>

  584. </thead>

  585. <tbody>

  586. <tr class="row-even"><td><dl class="c macro">

  587. <dt class="sig sig-object c" id="c.PyBUF_FULL">

  588. <span class="sig-name descname"><span class="n"><span class="pre">PyBUF_FULL</span></span></span><a class="headerlink" href="#c.PyBUF_FULL" title="Link to this definition">¶</a><br /></dt>

  589. <dd></dd></dl>

  590. 

  591. </td>

  592. <td><p>yes</p></td>

  593. <td><p>yes</p></td>

  594. <td><p>if needed</p></td>

  595. <td><p>U</p></td>

  596. <td><p>0</p></td>

  597. <td><p>yes</p></td>

  598. </tr>

  599. <tr class="row-odd"><td><dl class="c macro">

  600. <dt class="sig sig-object c" id="c.PyBUF_FULL_RO">

  601. <span class="sig-name descname"><span class="n"><span class="pre">PyBUF_FULL_RO</span></span></span><a class="headerlink" href="#c.PyBUF_FULL_RO" title="Link to this definition">¶</a><br /></dt>

  602. <dd></dd></dl>

  603. 

  604. </td>

  605. <td><p>yes</p></td>

  606. <td><p>yes</p></td>

  607. <td><p>if needed</p></td>

  608. <td><p>U</p></td>

  609. <td><p>1 or 0</p></td>

  610. <td><p>yes</p></td>

  611. </tr>

  612. <tr class="row-even"><td><dl class="c macro">

  613. <dt class="sig sig-object c" id="c.PyBUF_RECORDS">

  614. <span class="sig-name descname"><span class="n"><span class="pre">PyBUF_RECORDS</span></span></span><a class="headerlink" href="#c.PyBUF_RECORDS" title="Link to this definition">¶</a><br /></dt>

  615. <dd></dd></dl>

  616. 

  617. </td>

  618. <td><p>yes</p></td>

  619. <td><p>yes</p></td>

  620. <td><p>NULL</p></td>

  621. <td><p>U</p></td>

  622. <td><p>0</p></td>

  623. <td><p>yes</p></td>

  624. </tr>

  625. <tr class="row-odd"><td><dl class="c macro">

  626. <dt class="sig sig-object c" id="c.PyBUF_RECORDS_RO">

  627. <span class="sig-name descname"><span class="n"><span class="pre">PyBUF_RECORDS_RO</span></span></span><a class="headerlink" href="#c.PyBUF_RECORDS_RO" title="Link to this definition">¶</a><br /></dt>

  628. <dd></dd></dl>

  629. 

  630. </td>

  631. <td><p>yes</p></td>

  632. <td><p>yes</p></td>

  633. <td><p>NULL</p></td>

  634. <td><p>U</p></td>

  635. <td><p>1 or 0</p></td>

  636. <td><p>yes</p></td>

  637. </tr>

  638. <tr class="row-even"><td><dl class="c macro">

  639. <dt class="sig sig-object c" id="c.PyBUF_STRIDED">

  640. <span class="sig-name descname"><span class="n"><span class="pre">PyBUF_STRIDED</span></span></span><a class="headerlink" href="#c.PyBUF_STRIDED" title="Link to this definition">¶</a><br /></dt>

  641. <dd></dd></dl>

  642. 

  643. </td>

  644. <td><p>yes</p></td>

  645. <td><p>yes</p></td>

  646. <td><p>NULL</p></td>

  647. <td><p>U</p></td>

  648. <td><p>0</p></td>

  649. <td><p>NULL</p></td>

  650. </tr>

  651. <tr class="row-odd"><td><dl class="c macro">

  652. <dt class="sig sig-object c" id="c.PyBUF_STRIDED_RO">

  653. <span class="sig-name descname"><span class="n"><span class="pre">PyBUF_STRIDED_RO</span></span></span><a class="headerlink" href="#c.PyBUF_STRIDED_RO" title="Link to this definition">¶</a><br /></dt>

  654. <dd></dd></dl>

  655. 

  656. </td>

  657. <td><p>yes</p></td>

  658. <td><p>yes</p></td>

  659. <td><p>NULL</p></td>

  660. <td><p>U</p></td>

  661. <td><p>1 or 0</p></td>

  662. <td><p>NULL</p></td>

  663. </tr>

  664. <tr class="row-even"><td><dl class="c macro">

  665. <dt class="sig sig-object c" id="c.PyBUF_CONTIG">

  666. <span class="sig-name descname"><span class="n"><span class="pre">PyBUF_CONTIG</span></span></span><a class="headerlink" href="#c.PyBUF_CONTIG" title="Link to this definition">¶</a><br /></dt>

  667. <dd></dd></dl>

  668. 

  669. </td>

  670. <td><p>yes</p></td>

  671. <td><p>NULL</p></td>

  672. <td><p>NULL</p></td>

  673. <td><p>C</p></td>

  674. <td><p>0</p></td>

  675. <td><p>NULL</p></td>

  676. </tr>

  677. <tr class="row-odd"><td><dl class="c macro">

  678. <dt class="sig sig-object c" id="c.PyBUF_CONTIG_RO">

  679. <span class="sig-name descname"><span class="n"><span class="pre">PyBUF_CONTIG_RO</span></span></span><a class="headerlink" href="#c.PyBUF_CONTIG_RO" title="Link to this definition">¶</a><br /></dt>

  680. <dd></dd></dl>

  681. 

  682. </td>

  683. <td><p>yes</p></td>

  684. <td><p>NULL</p></td>

  685. <td><p>NULL</p></td>

  686. <td><p>C</p></td>

  687. <td><p>1 or 0</p></td>

  688. <td><p>NULL</p></td>

  689. </tr>

  690. </tbody>

  691. </table>

  692. </section>

  693. </section>

  694. <section id="complex-arrays">

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

  696. <section id="numpy-style-shape-and-strides">

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

  698. <p>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"><span class="pre">itemsize</span></code></a>,

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

  700. <p>If <code class="docutils literal notranslate"><span class="pre">ndim</span> <span class="pre">==</span> <span class="pre">0</span></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"><span class="pre">buf</span></code></a> is

  701. 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"><span class="pre">itemsize</span></code></a>. In that case,

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

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

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

  705. n-dimensional array as follows:</p>

  706. <div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="n">ptr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">char</span><span class="w"> </span><span class="o">*</span><span class="p">)</span><span class="n">buf</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">indices</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">strides</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p">...</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">indices</span><span class="p">[</span><span class="n">n</span><span class="mi">-1</span><span class="p">]</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">strides</span><span class="p">[</span><span class="n">n</span><span class="mi">-1</span><span class="p">];</span>

  707. <span class="n">item</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">*</span><span class="p">((</span><span class="n">typeof</span><span class="p">(</span><span class="n">item</span><span class="p">)</span><span class="w"> </span><span class="o">*</span><span class="p">)</span><span class="n">ptr</span><span class="p">);</span>

  708. </pre></div>

  709. </div>

  710. <p>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"><span class="pre">buf</span></code></a> can point to any location within

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

  712. this function:</p>

  713. <div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="k">def</span> <span class="nf">verify_structure</span><span class="p">(</span><span class="n">memlen</span><span class="p">,</span> <span class="n">itemsize</span><span class="p">,</span> <span class="n">ndim</span><span class="p">,</span> <span class="n">shape</span><span class="p">,</span> <span class="n">strides</span><span class="p">,</span> <span class="n">offset</span><span class="p">):</span>

  714. <span class="w">    </span><span class="sd">&quot;&quot;&quot;Verify that the parameters represent a valid array within</span>

  715. <span class="sd">       the bounds of the allocated memory:</span>

  716. <span class="sd">           char *mem: start of the physical memory block</span>

  717. <span class="sd">           memlen: length of the physical memory block</span>

  718. <span class="sd">           offset: (char *)buf - mem</span>

  719. <span class="sd">    &quot;&quot;&quot;</span>

  720.     <span class="k">if</span> <span class="n">offset</span> <span class="o">%</span> <span class="n">itemsize</span><span class="p">:</span>

  721.         <span class="k">return</span> <span class="kc">False</span>

  722.     <span class="k">if</span> <span class="n">offset</span> <span class="o">&lt;</span> <span class="mi">0</span> <span class="ow">or</span> <span class="n">offset</span><span class="o">+</span><span class="n">itemsize</span> <span class="o">&gt;</span> <span class="n">memlen</span><span class="p">:</span>

  723.         <span class="k">return</span> <span class="kc">False</span>

  724.     <span class="k">if</span> <span class="nb">any</span><span class="p">(</span><span class="n">v</span> <span class="o">%</span> <span class="n">itemsize</span> <span class="k">for</span> <span class="n">v</span> <span class="ow">in</span> <span class="n">strides</span><span class="p">):</span>

  725.         <span class="k">return</span> <span class="kc">False</span>

  726. 

  727.     <span class="k">if</span> <span class="n">ndim</span> <span class="o">&lt;=</span> <span class="mi">0</span><span class="p">:</span>

  728.         <span class="k">return</span> <span class="n">ndim</span> <span class="o">==</span> <span class="mi">0</span> <span class="ow">and</span> <span class="ow">not</span> <span class="n">shape</span> <span class="ow">and</span> <span class="ow">not</span> <span class="n">strides</span>

  729.     <span class="k">if</span> <span class="mi">0</span> <span class="ow">in</span> <span class="n">shape</span><span class="p">:</span>

  730.         <span class="k">return</span> <span class="kc">True</span>

  731. 

  732.     <span class="n">imin</span> <span class="o">=</span> <span class="nb">sum</span><span class="p">(</span><span class="n">strides</span><span class="p">[</span><span class="n">j</span><span class="p">]</span><span class="o">*</span><span class="p">(</span><span class="n">shape</span><span class="p">[</span><span class="n">j</span><span class="p">]</span><span class="o">-</span><span class="mi">1</span><span class="p">)</span> <span class="k">for</span> <span class="n">j</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="n">ndim</span><span class="p">)</span>

  733.                <span class="k">if</span> <span class="n">strides</span><span class="p">[</span><span class="n">j</span><span class="p">]</span> <span class="o">&lt;=</span> <span class="mi">0</span><span class="p">)</span>

  734.     <span class="n">imax</span> <span class="o">=</span> <span class="nb">sum</span><span class="p">(</span><span class="n">strides</span><span class="p">[</span><span class="n">j</span><span class="p">]</span><span class="o">*</span><span class="p">(</span><span class="n">shape</span><span class="p">[</span><span class="n">j</span><span class="p">]</span><span class="o">-</span><span class="mi">1</span><span class="p">)</span> <span class="k">for</span> <span class="n">j</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="n">ndim</span><span class="p">)</span>

  735.                <span class="k">if</span> <span class="n">strides</span><span class="p">[</span><span class="n">j</span><span class="p">]</span> <span class="o">&gt;</span> <span class="mi">0</span><span class="p">)</span>

  736. 

  737.     <span class="k">return</span> <span class="mi">0</span> <span class="o">&lt;=</span> <span class="n">offset</span><span class="o">+</span><span class="n">imin</span> <span class="ow">and</span> <span class="n">offset</span><span class="o">+</span><span class="n">imax</span><span class="o">+</span><span class="n">itemsize</span> <span class="o">&lt;=</span> <span class="n">memlen</span>

  738. </pre></div>

  739. </div>

  740. </section>

  741. <section id="pil-style-shape-strides-and-suboffsets">

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

  743. <p>In addition to the regular items, PIL-style arrays can contain pointers

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

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

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

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

  748. 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"><span class="pre">buf</span></code></a>, pointing

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

  750. <p>Here is a function that returns a pointer to the element in an N-D array

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

  752. and suboffsets:</p>

  753. <div class="highlight-c notranslate"><div class="highlight"><pre><span></span><span class="kt">void</span><span class="w"> </span><span class="o">*</span><span class="nf">get_item_pointer</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">ndim</span><span class="p">,</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="o">*</span><span class="n">buf</span><span class="p">,</span><span class="w"> </span><span class="n">Py_ssize_t</span><span class="w"> </span><span class="o">*</span><span class="n">strides</span><span class="p">,</span>

  754. <span class="w">                       </span><span class="n">Py_ssize_t</span><span class="w"> </span><span class="o">*</span><span class="n">suboffsets</span><span class="p">,</span><span class="w"> </span><span class="n">Py_ssize_t</span><span class="w"> </span><span class="o">*</span><span class="n">indices</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>

  755. <span class="w">    </span><span class="kt">char</span><span class="w"> </span><span class="o">*</span><span class="n">pointer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">char</span><span class="o">*</span><span class="p">)</span><span class="n">buf</span><span class="p">;</span>

  756. <span class="w">    </span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="p">;</span>

  757. <span class="w">    </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">ndim</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>

  758. <span class="w">        </span><span class="n">pointer</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">strides</span><span class="p">[</span><span class="n">i</span><span class="p">]</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">indices</span><span class="p">[</span><span class="n">i</span><span class="p">];</span>

  759. <span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">suboffsets</span><span class="p">[</span><span class="n">i</span><span class="p">]</span><span class="w"> </span><span class="o">&gt;=</span><span class="mi">0</span><span class="w"> </span><span class="p">)</span><span class="w"> </span><span class="p">{</span>

  760. <span class="w">            </span><span class="n">pointer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">*</span><span class="p">((</span><span class="kt">char</span><span class="o">**</span><span class="p">)</span><span class="n">pointer</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">suboffsets</span><span class="p">[</span><span class="n">i</span><span class="p">];</span>

  761. <span class="w">        </span><span class="p">}</span>

  762. <span class="w">    </span><span class="p">}</span>

  763. <span class="w">    </span><span class="k">return</span><span class="w"> </span><span class="p">(</span><span class="kt">void</span><span class="o">*</span><span class="p">)</span><span class="n">pointer</span><span class="p">;</span>

  764. <span class="p">}</span>

  765. </pre></div>

  766. </div>

  767. </section>

  768. </section>

  769. <section id="buffer-related-functions">

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

  771. <dl class="c function">

  772. <dt class="sig sig-object c" id="c.PyObject_CheckBuffer">

  773. <span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyObject_CheckBuffer</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n"><span class="pre">PyObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">obj</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyObject_CheckBuffer" title="Link to this definition">¶</a><br /></dt>

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

  775. 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"><span class="pre">PyObject_GetBuffer()</span></code></a> will

  776. succeed.  This function always succeeds.</p>

  777. </dd></dl>

  778. 

  779. <dl class="c function">

  780. <dt class="sig sig-object c" id="c.PyObject_GetBuffer">

  781. <span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyObject_GetBuffer</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n"><span class="pre">PyObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">exporter</span></span>, <a class="reference internal" href="#c.Py_buffer" title="Py_buffer"><span class="n"><span class="pre">Py_buffer</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">view</span></span>, <span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="n"><span class="pre">flags</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyObject_GetBuffer" title="Link to this definition">¶</a><br /></dt>

  782. <dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a> since version 3.11.</em><p>Send a request to <em>exporter</em> to fill in <em>view</em> as specified by  <em>flags</em>.

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

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

  785. return <code class="docutils literal notranslate"><span class="pre">-1</span></code>.</p>

  786. <p>On success, fill in <em>view</em>, set <code class="docutils literal notranslate"><span class="pre">view-&gt;obj</span></code> to a new reference

  787. to <em>exporter</em> and return 0. In the case of chained buffer providers

  788. that redirect requests to a single object, <code class="docutils literal notranslate"><span class="pre">view-&gt;obj</span></code> MAY

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

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

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

  792. 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"><span class="pre">PyBuffer_Release()</span></code></a>

  793. must be called exactly once.</p>

  794. </dd></dl>

  795. 

  796. <dl class="c function">

  797. <dt class="sig sig-object c" id="c.PyBuffer_Release">

  798. <span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyBuffer_Release</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.Py_buffer" title="Py_buffer"><span class="n"><span class="pre">Py_buffer</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">view</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyBuffer_Release" title="Link to this definition">¶</a><br /></dt>

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

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

  801. <code class="docutils literal notranslate"><span class="pre">view-&gt;obj</span></code>. This function MUST be called when the buffer

  802. is no longer being used, otherwise reference leaks may occur.</p>

  803. <p>It is an error to call this function on a buffer that was not obtained via

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

  805. </dd></dl>

  806. 

  807. <dl class="c function">

  808. <dt class="sig sig-object c" id="c.PyBuffer_SizeFromFormat">

  809. <a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t"><span class="n"><span class="pre">Py_ssize_t</span></span></a><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyBuffer_SizeFromFormat</span></span></span><span class="sig-paren">(</span><span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="kt"><span class="pre">char</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">format</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyBuffer_SizeFromFormat" title="Link to this definition">¶</a><br /></dt>

  810. <dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a> since version 3.11.</em><p>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"><span class="pre">itemsize</span></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"><span class="pre">format</span></code></a>.

  811. On error, raise an exception and return -1.</p>

  812. <div class="versionadded">

  813. <p><span class="versionmodified added">New in version 3.9.</span></p>

  814. </div>

  815. </dd></dl>

  816. 

  817. <dl class="c function">

  818. <dt class="sig sig-object c" id="c.PyBuffer_IsContiguous">

  819. <span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyBuffer_IsContiguous</span></span></span><span class="sig-paren">(</span><span class="k"><span class="pre">const</span></span><span class="w"> </span><a class="reference internal" href="#c.Py_buffer" title="Py_buffer"><span class="n"><span class="pre">Py_buffer</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">view</span></span>, <span class="kt"><span class="pre">char</span></span><span class="w"> </span><span class="n"><span class="pre">order</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyBuffer_IsContiguous" title="Link to this definition">¶</a><br /></dt>

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

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

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

  823. </dd></dl>

  824. 

  825. <dl class="c function">

  826. <dt class="sig sig-object c" id="c.PyBuffer_GetPointer">

  827. <span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">PyBuffer_GetPointer</span></span></span><span class="sig-paren">(</span><span class="k"><span class="pre">const</span></span><span class="w"> </span><a class="reference internal" href="#c.Py_buffer" title="Py_buffer"><span class="n"><span class="pre">Py_buffer</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">view</span></span>, <span class="k"><span class="pre">const</span></span><span class="w"> </span><a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t"><span class="n"><span class="pre">Py_ssize_t</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">indices</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyBuffer_GetPointer" title="Link to this definition">¶</a><br /></dt>

  828. <dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a> since version 3.11.</em><p>Get the memory area pointed to by the <em>indices</em> inside the given <em>view</em>.

  829. <em>indices</em> must point to an array of <code class="docutils literal notranslate"><span class="pre">view-&gt;ndim</span></code> indices.</p>

  830. </dd></dl>

  831. 

  832. <dl class="c function">

  833. <dt class="sig sig-object c" id="c.PyBuffer_FromContiguous">

  834. <span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyBuffer_FromContiguous</span></span></span><span class="sig-paren">(</span><span class="k"><span class="pre">const</span></span><span class="w"> </span><a class="reference internal" href="#c.Py_buffer" title="Py_buffer"><span class="n"><span class="pre">Py_buffer</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">view</span></span>, <span class="k"><span class="pre">const</span></span><span class="w"> </span><span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">buf</span></span>, <a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t"><span class="n"><span class="pre">Py_ssize_t</span></span></a><span class="w"> </span><span class="n"><span class="pre">len</span></span>, <span class="kt"><span class="pre">char</span></span><span class="w"> </span><span class="n"><span class="pre">fort</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyBuffer_FromContiguous" title="Link to this definition">¶</a><br /></dt>

  835. <dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a> since version 3.11.</em><p>Copy contiguous <em>len</em> bytes from <em>buf</em> to <em>view</em>.

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

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

  838. </dd></dl>

  839. 

  840. <dl class="c function">

  841. <dt class="sig sig-object c" id="c.PyBuffer_ToContiguous">

  842. <span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyBuffer_ToContiguous</span></span></span><span class="sig-paren">(</span><span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">buf</span></span>, <span class="k"><span class="pre">const</span></span><span class="w"> </span><a class="reference internal" href="#c.Py_buffer" title="Py_buffer"><span class="n"><span class="pre">Py_buffer</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">src</span></span>, <a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t"><span class="n"><span class="pre">Py_ssize_t</span></span></a><span class="w"> </span><span class="n"><span class="pre">len</span></span>, <span class="kt"><span class="pre">char</span></span><span class="w"> </span><span class="n"><span class="pre">order</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyBuffer_ToContiguous" title="Link to this definition">¶</a><br /></dt>

  843. <dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a> since version 3.11.</em><p>Copy <em>len</em> bytes from <em>src</em> to its contiguous representation in <em>buf</em>.

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

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

  846. <p>This function fails if <em>len</em> != <em>src-&gt;len</em>.</p>

  847. </dd></dl>

  848. 

  849. <dl class="c function">

  850. <dt class="sig sig-object c" id="c.PyObject_CopyData">

  851. <span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyObject_CopyData</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n"><span class="pre">PyObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">dest</span></span>, <a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n"><span class="pre">PyObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">src</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyObject_CopyData" title="Link to this definition">¶</a><br /></dt>

  852. <dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a> since version 3.11.</em><p>Copy data from <em>src</em> to <em>dest</em> buffer. Can convert between C-style and

  853. or Fortran-style buffers.</p>

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

  855. </dd></dl>

  856. 

  857. <dl class="c function">

  858. <dt class="sig sig-object c" id="c.PyBuffer_FillContiguousStrides">

  859. <span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyBuffer_FillContiguousStrides</span></span></span><span class="sig-paren">(</span><span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="n"><span class="pre">ndims</span></span>, <a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t"><span class="n"><span class="pre">Py_ssize_t</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">shape</span></span>, <a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t"><span class="n"><span class="pre">Py_ssize_t</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">strides</span></span>, <span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="n"><span class="pre">itemsize</span></span>, <span class="kt"><span class="pre">char</span></span><span class="w"> </span><span class="n"><span class="pre">order</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyBuffer_FillContiguousStrides" title="Link to this definition">¶</a><br /></dt>

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

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

  862. given shape with the given number of bytes per element.</p>

  863. </dd></dl>

  864. 

  865. <dl class="c function">

  866. <dt class="sig sig-object c" id="c.PyBuffer_FillInfo">

  867. <span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyBuffer_FillInfo</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="#c.Py_buffer" title="Py_buffer"><span class="n"><span class="pre">Py_buffer</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">view</span></span>, <a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n"><span class="pre">PyObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">exporter</span></span>, <span class="kt"><span class="pre">void</span></span><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">buf</span></span>, <a class="reference internal" href="intro.html#c.Py_ssize_t" title="Py_ssize_t"><span class="n"><span class="pre">Py_ssize_t</span></span></a><span class="w"> </span><span class="n"><span class="pre">len</span></span>, <span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="n"><span class="pre">readonly</span></span>, <span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="n"><span class="pre">flags</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyBuffer_FillInfo" title="Link to this definition">¶</a><br /></dt>

  868. <dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a> since version 3.11.</em><p>Handle buffer requests for an exporter that wants to expose <em>buf</em> of size <em>len</em>

  869. with writability set according to <em>readonly</em>. <em>buf</em> is interpreted as a sequence

  870. of unsigned bytes.</p>

  871. <p>The <em>flags</em> argument indicates the request type. This function always fills in

  872. <em>view</em> as specified by flags, unless <em>buf</em> has been designated as read-only

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

  874. <p>On success, set <code class="docutils literal notranslate"><span class="pre">view-&gt;obj</span></code> to a new reference to <em>exporter</em> and

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

  876. <code class="docutils literal notranslate"><span class="pre">view-&gt;obj</span></code> to <code class="docutils literal notranslate"><span class="pre">NULL</span></code> and return <code class="docutils literal notranslate"><span class="pre">-1</span></code>;</p>

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

  878. <em>exporter</em> MUST be set to the exporting object and <em>flags</em> must be passed

  879. unmodified. Otherwise, <em>exporter</em> MUST be <code class="docutils literal notranslate"><span class="pre">NULL</span></code>.</p>

  880. </dd></dl>

  881. 

  882. </section>

  883. </section>

  884. 

  885. 

  886.             <div class="clearer"></div>

  887.           </div>

  888.         </div>

  889.       </div>

  890.       <div class="sphinxsidebar" role="navigation" aria-label="main navigation">

  891.         <div class="sphinxsidebarwrapper">

  892.   <div>

  893.     <h3><a href="../contents.html">Table of Contents</a></h3>

  894.     <ul>

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

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

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

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

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

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

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

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

  903. </ul>

  904. </li>

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

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

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

  908. </ul>

  909. </li>

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

  911. </ul>

  912. </li>

  913. </ul>

  914. 

  915.   </div>

  916.   <div>

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