matheusgadelha / cnpy

library to read/write .npy and .npz files in C/C++

CNPY

Small library to read and write Numpy data with C++ Eigen arrays. This version includes a Makefile-based build (instead of CMake) and support to Eigen.

Requirements:

1. zlib
2. eigen

Building from source

Building from source is straightforward. Just run make and it will generate a static library and a sample binary.

Using:

To use, #include"cnpy.h" in your source code. Compile the source code mycode.cpp as

g++ -o mycode mycode.cpp -L/path/to/install/dir -lcnpy

Description:

There are two functions for writing data: npy_save, npz_save.

There are 3 functions for reading. npy_load will load a .npy file. npz_load(fname) will load a .npz and return a dictionary of NpyArray structues. npz_load(fname,varname) will load and return the NpyArray for data varname from the specified .npz file. Note that NpyArray allocates char* data using new[] and will not delete the data upon the NpyArray destruction. You are responsible for delete the data yourself.

The data structure for loaded data is below. Data is loaded into a a raw byte array. The array shape and word size are read from the npy header. You are responsible for casting/copying the data to its intended data type.

struct NpyArray {
    char* data;
    std::vector<unsigned int> shape;
    unsigned int word_size;
};

See example1.cpp for examples of how to use the library. example1 will also be build during cmake installation.