Receive packed array via WSTP

method_1.cpp

#include <stdlib.h>
#include <vector>
#include <string>
#include "wstp.h"

using namespace std;

int main() {
    int err;
    auto env_p = WSInitialize((void*)0);
    auto link_p = WSOpenString(env_p, "-linkname someLink -linkmode connect", &err);
    if (err != WSEOK) { /* error ... */ }

    auto token = WSGetType(link_p);
    auto raw_token = WSGetRawType(link_p);

    auto temp_link_p = WSLoopbackOpen(env_p, &err);
    if (err != WSEOK) { /* error ... */ }
    array_meterp am;
    long depth;

    vector<int> shape;
    vector<string> heads;
    size_t total_size = 1;
    const char *head_p;
    int argcount;
    int elem_token;
    auto mark = WSCreateMark(link_p);

    do {
        WSGetFunction(link_p, &head_p, &argcount);
        total_size *= argcount;
        shape.push_back(argcount);
        heads.push_back(string(head_p));
        WSReleaseSymbol(link_p, head_p);
        elem_token = WSGetRawType(link_p);
    } while (elem_token == WSTKFUNC);

    switch (elem_token) {
    case WSTK_CDOUBLE:
        total_size *= sizeof(double);
        break;
    case WSTK_CFLOAT:
        total_size *= sizeof(float);
        break;
    default:
        /* error ... */
        break;
    }

    WSSeekToMark(link_p, mark, 0);
    WSDestroyMark(link_p, mark);

    void *array_data;
    long *received_dims;
    char **received_heads;
    long received_depth;

    WSGetBinaryNumberArray(
        link_p, &array_data, &received_dims, &received_heads, &received_depth, elem_token);

    /* do stuff with array */

    // there is a int/long mismatch on received_dims, I don't understand why
    WSReleaseBinaryNumberArray(
        link_p, array_data, (int*)received_dims, received_heads, total_size, elem_token);

    return 0;
}

method_2.cpp

#include <stdlib.h>
#include <vector>
#include <string>
#include "wstp.h"

using namespace std;

int main() {
    int err;
    auto env_p = WSInitialize((void*)0);
    auto link_p = WSOpenString(env_p, "-linkname someLink -linkmode connect", &err);
    if (err != WSEOK) { /* error ... */ }

    auto token = WSGetType(link_p);
    auto raw_token = WSGetRawType(link_p);

    auto temp_link_p = WSLoopbackOpen(env_p, &err);
    if (err != WSEOK) { /* error ... */ }
    array_meterp am;
    long depth;
    mlapi__token leaf_token; // this token seems unused

    if (!WSGetArrayTypeWithDepthAndLeafType(link_p, temp_link_p, &am, &depth, &leaf_token)) {
        /* error ... */
    }

    size_t total_size = 1;
    const char *head_p;
    int argcount;
    vector<int> shape;
    vector<string> heads;

    for (int i=0; i<depth; ++i) {
        WSGetFunction(temp_link_p, &head_p, &argcount);
        total_size *= argcount;
        shape.push_back(argcount);
        heads.push_back(string(head_p));
        WSReleaseSymbol(link_p, head_p);
    }

    auto elem_token = WSGetRawType(link_p);

    switch (elem_token) {
    case WSTK_CDOUBLE:
        total_size *= sizeof(double);
        break;
    case WSTK_CFLOAT:
        total_size *= sizeof(float);
        break;
    default:
        /* error ... */
        break;
    }

    void *array_data = malloc(total_size);
    WSGetBinaryNumberArrayData(link_p, am, array_data, total_size, elem_token);
    WSReleaseGetArrayState(link_p, temp_link_p, am);
    WSClose(temp_link_p);

    /* do stuff with array */

    free(array_data);
    return 0;
}

server.m

(* run this first, then compiled c++ program *)
link = LinkCreate["someLink", LinkMode->Listen];
LinkWrite[link, RandomReal[1., {4,4}]];
InputString["Done"];
LinkClose[link];