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Add Python buffer api support
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‎AUTHORS.md

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- ([@OneBlue](https://github.com/OneBlue))
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- ([@rico-chet](https://github.com/rico-chet))
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- ([@rmadsen-ks](https://github.com/rmadsen-ks))
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- ([@SnGmng](https://github.com/SnGmng))
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- ([@stonebig](https://github.com/stonebig))
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- ([@testrunner123](https://github.com/testrunner123))
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‎CHANGELOG.md

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@@ -18,6 +18,7 @@ This document follows the conventions laid out in [Keep a CHANGELOG][].
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- Added Runtime.None to be able to pass None as parameter into Python from .NET
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- Added PyObject.IsNone() to check if a Python object is None in .NET.
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- Support for Python 3.8
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- Added Python 3 buffer api support and PyBuffer interface for fast byte and numpy array read/write ([#980][p980])
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### Changed
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‎src/embed_tests/Python.EmbeddingTest.csproj

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<Compile Include="TestFinalizer.cs" />
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<Compile Include="TestInstanceWrapping.cs" />
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<Compile Include="TestPyAnsiString.cs" />
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<Compile Include="TestPyBuffer.cs" />
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<Compile Include="TestPyFloat.cs" />
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<Compile Include="TestPyInt.cs" />
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<Compile Include="TestPyList.cs" />

‎src/embed_tests/TestPyBuffer.cs

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using System.Text;
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using NUnit.Framework;
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using Python.Runtime;
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namespace Python.EmbeddingTest {
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class TestPyBuffer
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{
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[OneTimeSetUp]
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public void SetUp()
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{
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PythonEngine.Initialize();
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}
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[OneTimeTearDown]
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public void Dispose()
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{
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PythonEngine.Shutdown();
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}
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[Test]
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public void TestBufferWrite()
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{
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if (Runtime.Runtime.pyversionnumber < 35) return;
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string bufferTestString = "hello world! !$%&/()=?";
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using (Py.GIL())
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{
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using (var scope = Py.CreateScope())
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{
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scope.Exec($"arr = bytearray({bufferTestString.Length})");
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PyObject pythonArray = scope.Get("arr");
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byte[] managedArray = new UTF8Encoding().GetBytes(bufferTestString);
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using (PyBuffer buf = pythonArray.GetBuffer())
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{
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buf.Write(managedArray, 0, managedArray.Length);
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}
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string result = scope.Eval("arr.decode('utf-8')").ToString();
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Assert.IsTrue(result == bufferTestString);
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}
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}
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}
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[Test]
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public void TestBufferRead()
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{
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if (Runtime.Runtime.pyversionnumber < 35) return;
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string bufferTestString = "hello world! !$%&/()=?";
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using (Py.GIL())
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{
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using (var scope = Py.CreateScope())
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{
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scope.Exec($"arr = b'{bufferTestString}'");
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PyObject pythonArray = scope.Get("arr");
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byte[] managedArray = new byte[bufferTestString.Length];
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using (PyBuffer buf = pythonArray.GetBuffer())
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{
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buf.Read(managedArray, 0, managedArray.Length);
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}
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string result = new UTF8Encoding().GetString(managedArray);
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Assert.IsTrue(result == bufferTestString);
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}
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}
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}
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}
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}

‎src/runtime/Python.Runtime.csproj

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<Compile Include="arrayobject.cs" />
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<Compile Include="assemblymanager.cs" />
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<Compile Include="BorrowedReference.cs" />
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<Compile Include="bufferinterface.cs" />
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<Compile Include="classderived.cs" />
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<Compile Include="classbase.cs" />
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<Compile Include="classmanager.cs" />
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<Compile Include="overload.cs" />
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<Compile Include="propertyobject.cs" />
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<Compile Include="pyansistring.cs" />
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<Compile Include="pybuffer.cs" />
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<Compile Include="pydict.cs" />
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<Compile Include="PyExportAttribute.cs" />
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<Compile Include="pyfloat.cs" />
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<Copy SourceFiles="$(TargetAssembly)" DestinationFolder="$(PythonBuildDir)" />
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<!--Copy SourceFiles="$(TargetAssemblyPdb)" Condition="Exists('$(TargetAssemblyPdb)')" DestinationFolder="$(PythonBuildDir)" /-->
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</Target>
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</Project>
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</Project>

‎src/runtime/bufferinterface.cs

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using System;
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using System.Runtime.InteropServices;
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namespace Python.Runtime
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{
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/* buffer interface */
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[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
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internal struct Py_buffer {
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public IntPtr buf;
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public IntPtr obj; /* owned reference */
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[MarshalAs(UnmanagedType.SysInt)]
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public IntPtr len;
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[MarshalAs(UnmanagedType.SysInt)]
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public IntPtr itemsize; /* This is Py_ssize_t so it can be
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pointed to by strides in simple case.*/
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[MarshalAs(UnmanagedType.Bool)]
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public bool _readonly;
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public int ndim;
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[MarshalAs(UnmanagedType.LPStr)]
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public string format;
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public IntPtr shape;
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public IntPtr strides;
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public IntPtr suboffsets;
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public IntPtr _internal;
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}
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public enum BufferOrderStyle
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{
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C,
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Fortran,
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EitherOne,
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}
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/* Flags for getting buffers */
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public enum PyBUF
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{
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/// <summary>
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/// Simple buffer without shape strides and suboffsets
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/// </summary>
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SIMPLE = 0,
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/// <summary>
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/// Controls the <see cref="PyBuffer.ReadOnly"/> 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.
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/// </summary>
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WRITABLE = 0x0001,
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/// <summary>
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/// Controls the <see cref="PyBuffer.Format"/> field. If set, this field MUST be filled in correctly. Otherwise, this field MUST be NULL.
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/// </summary>
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FORMATS = 0x0004,
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/// <summary>
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/// N-Dimensional buffer with shape
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/// </summary>
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ND = 0x0008,
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/// <summary>
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/// Buffer with strides and shape
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/// </summary>
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STRIDES = (0x0010 | ND),
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/// <summary>
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/// C-Contigous buffer with strides and shape
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/// </summary>
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C_CONTIGUOUS = (0x0020 | STRIDES),
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/// <summary>
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/// F-Contigous buffer with strides and shape
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/// </summary>
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F_CONTIGUOUS = (0x0040 | STRIDES),
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/// <summary>
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/// C or Fortran contigous buffer with strides and shape
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/// </summary>
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ANY_CONTIGUOUS = (0x0080 | STRIDES),
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/// <summary>
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/// Buffer with suboffsets (if needed)
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/// </summary>
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INDIRECT = (0x0100 | STRIDES),
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/// <summary>
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/// Writable C-Contigous buffer with shape
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/// </summary>
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CONTIG = (ND | WRITABLE),
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/// <summary>
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/// Readonly C-Contigous buffer with shape
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/// </summary>
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CONTIG_RO = (ND),
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/// <summary>
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/// Writable buffer with shape and strides
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/// </summary>
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STRIDED = (STRIDES | WRITABLE),
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/// <summary>
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/// Readonly buffer with shape and strides
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/// </summary>
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STRIDED_RO = (STRIDES),
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/// <summary>
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/// Writable buffer with shape, strides and format
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/// </summary>
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RECORDS = (STRIDES | WRITABLE | FORMATS),
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/// <summary>
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/// Readonly buffer with shape, strides and format
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/// </summary>
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RECORDS_RO = (STRIDES | FORMATS),
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/// <summary>
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/// Writable indirect buffer with shape, strides, format and suboffsets (if needed)
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/// </summary>
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FULL = (INDIRECT | WRITABLE | FORMATS),
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/// <summary>
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/// Readonly indirect buffer with shape, strides, format and suboffsets (if needed)
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/// </summary>
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FULL_RO = (INDIRECT | FORMATS),
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}
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}

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