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How to create an NDArray from pointer and NPTypeCode? #390

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How to create an NDArray from pointer and NPTypeCode?#390

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@LarryThermo
LarryThermo
opened on Jan 24, 2020

First of all thanks for this project.

My code calls into lower level C++ code and I wish to represent the returned array as an NDArray in C#. I have a pointer to the data, the length of the data in bytes, as well as type code. How would I go about creating an NDArray for this case? Something like:

NDArray CreateNDArray(void* data,int dataLengthBytes,NPTypeCode typeCode)
{
var storage = new UnmanagedStorage( "something here" );
var nda = new NDArray(storage);
return nda;
}

Thanks,

Lars

Activity

  1. LarryThermo
    changed the title [-]How to create and NDArray from pointer and NPTypeCode[/-] [+]How to create an NDArray from pointer and NPTypeCode?[/+] on Jan 24, 2020

  2. Oceania2018 commented on Jan 24, 2020

    @Oceania2018
    Oceania2018
    on Jan 24, 2020
    Member

    @LarryThermo This snippet of code will help you.

  3. LarryThermo commented on Jan 27, 2020

    @LarryThermo
    LarryThermo
    on Jan 27, 2020 via email
    Author

  4. Nucs commented on Sep 7, 2026

    @Nucs
    Nucs
    on Sep 7, 2026
    Member

    Use np.frombuffer (0.70.0, #628) to wrap a byte buffer as an NDArray of a given dtype:

    byte[] raw = new byte[16];
BitConverter.GetBytes(1.0).CopyTo(raw, 0);
BitConverter.GetBytes(2.0).CopyTo(raw, 8);

var nd = np.frombuffer(raw, "float64");   // also "int32" / "<f8" / NPTypeCode.Double
Console.WriteLine(nd);   // [1. 2.]

    For a raw T* pointer, wrap it in an UnmanagedMemoryBlock<T> and build the NDArray from that storage. Closing.

  5. Nucs
    closed this as completedon Sep 7, 2026
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