如何从 Octave 或 Matlab 中的文件加载 C 结构

Question

I have an array of C struct's like

typedef struct{
    uint32_t timestamp;
    uint16_t channels[4];
    float    value;
} sample_t;

Which is write to a file with something like

fwrite(&sample,sizeof(sample_t),1,fpLog)

What's a good way to load this into a array of struct in Octave/Matlab?

Edit: The goal is optimization for speed. The files are 1GB+ big and take a very long time to load in matlab. The files load 100x faster in numpy.

Answer 1

There is aligned rules for each C/C++ struct/class. See for example Eric Postpischil's answer in How is the size of a C++ class determined? . Very imported citate:

For elementary types (int, double, et cetera), the alignment requirements are implementation dependent and are largely determined by the hardware.

So aligned rules for C/C++ compiler and Matlab/Octave can be different. You can solve yore problem:

1. Write data to file by components:

    fwrite(&sample.timestamp,sizeof(sample.timestamp),1,fpLog) fwrite(sample.channels,sizeof(sample.channels[0]),sizeof(sample.channels)/sizof(sample.channels[0]),fpLog) fwrite(&sample.value,sizeof(sample.value),1,fpLog) 

2. Read file in Matlab/Octave by componets too:

    ts = fread(fplog,"uint32"); sample.timestamp = ts; ch = fread(fplog,"uint16",4); sample.channels = ch; vl = fread(fplog,"float32"); sample.value = vl; sample 

Do not forget to open files in binary mode!!!

Answer 2

A trick : one can generate the .m I/O statements by parsing the C-struct definition with the GDB Python API . When the binary file to read is produced by an ELF/object/executable and you have a Debug (gcc -g) version of it.