ccall julia

vector2.c

#include <stdlib.h>
#include <stdio.h>

// gcc -shared -o vector2.so vector2.c

typedef struct Vec {
    long int length;
    double* data;
} Vec;

Vec new_vector(long int length) {
    Vec v;
    v.length = length;
    v.data = malloc(sizeof(double) * length);
    return v;
}

void set_vector_data(Vec *v, long int i, double val) {
    v->data[i] = val;
}

double get_vector_data(Vec *v, long int i) {
    return v->data[i];
}

int main(int argc, char* argv[]) {
    Vec vec = new_vector(3);
    Vec* vecp = &vec;

    set_vector_data(vecp, 0, 1.5);
    set_vector_data(vecp, 1, 2.5);
    set_vector_data(vecp, 2, 3.5);
    printf("v[0] = %f\n", get_vector_data(vecp, 0));
    printf("v[1] = %f\n", get_vector_data(vecp, 1));
    printf("v[2] = %f\n", get_vector_data(vecp, 2));
}

vector2.jl

const lib = "./vector2.so"

mutable struct Vec
    length :: Int
    data :: Ptr{Cdouble}
end

function Vector(n::Int)
    return ccall((:new_vector, lib), Vec, (Cint, ), n)
end

function set_vector_data(v, i::Int, val::Float64)
    ccall((:set_vector_data, lib), Cvoid, (Ptr{Vec}, Clong, Cdouble), Ref(v), i, val)
end

function get_vector_data(v::Vec, i::Int)
    return ccall((:get_vector_data, lib), Cdouble, (Ptr{Vec}, Cint, ), Ref(v), i)
end

function test()
    println("test 1 start")
    v = Vector(3)
    println(v)
    set_vector_data(v, 0, 1.5)
    set_vector_data(v, 1, 2.5)
    set_vector_data(v, 2, 3.5)
    for i=1:3
        println("unsafe_load, v.data[$i] = ", unsafe_load(v.data, i))
    end

    data = unsafe_wrap(Array, v.data, 3; own = false)
    println("data = ", data)
    data[2] += 5

    for i=0:2
        println("v[$i] = $(get_vector_data(v, i))")
    end
    println("test 1 end")
end

function test2()
    println("test 2 start")
    data = [1.5, 2.5, 3.5]
    v = Vec(3, pointer(data))
    println(v)

    data[2] += 5
    println("data = ", data)

    for i=0:2
        println("v[$i] = $(get_vector_data(v, i))")
    end
    println("test 2 end")
end

test()
test2()