docs.sheetjs.com/docz/static/hermes/sheetjs-hermes.cpp

/* sheetjs-hermes.cpp Copyright (c) SheetJS LLC. */
#include <iostream>
#include "hermes/hermes.h"

static char *read_file(const char *filename, size_t *sz) {
  FILE *f = fopen(filename, "rb");
  if(!f) return NULL;
  long fsize; { fseek(f, 0, SEEK_END); fsize = ftell(f); fseek(f, 0, SEEK_SET); }
  char *buf = (char *)malloc(fsize * sizeof(char));
  *sz = fread((void *) buf, 1, fsize, f);
  fclose(f);
  return buf;
}

/* Unfortunately the library provides no C-friendly Buffer classes */
class CBuffer : public facebook::jsi::Buffer {
  public:
    CBuffer(const uint8_t *data, size_t size) : buf(data), sz(size) {}
    size_t size() const override { return sz; }
    const uint8_t *data() const override { return buf; }

  private:
    const uint8_t *buf;
    size_t sz;
};
/* ArrayBuffer constructor expects MutableBuffer*/
class CMutableBuffer : public facebook::jsi::MutableBuffer {
  public:
    CMutableBuffer(uint8_t *data, size_t size) : buf(data), sz(size) {}
    size_t size() const override { return sz; }
    uint8_t *data() override { return buf; }

  private:
    uint8_t *buf;
    size_t sz;
};

int main(int argc, char **argv) {
  std::unique_ptr<facebook::jsi::Runtime> rt(facebook::hermes::makeHermesRuntime());

  /* setup */
  try {
    auto src = std::make_shared<facebook::jsi::StringBuffer>(
      "var global = (function(){ return this; }).call(null);"
      "var console = { log: function(x) { print(x); } };"
    );
    auto js = rt->prepareJavaScript(src, std::string("<eval>"));
    rt->evaluatePreparedJavaScript(js);
  } catch (const facebook::jsi::JSIException &e) {
    std::cerr << "JavaScript terminated via uncaught exception: " << e.what() << '\n';
    return 1;
  }

  /* load SheetJS library */
  try {
    size_t sz; char *xlsx_full_min_js = read_file("xlsx.full.min.js", &sz);
    auto src = std::make_shared<CBuffer>(CBuffer((uint8_t *)xlsx_full_min_js, sz));
    auto js = rt->prepareJavaScript(src, std::string("xlsx.full.min.js"));
    rt->evaluatePreparedJavaScript(js);
  } catch (const facebook::jsi::JSIException &e) {
    std::cerr << "JavaScript terminated via uncaught exception: " << e.what() << '\n';
    return 1;
  }

  /* print library version */
  try {
    auto src = std::make_shared<facebook::jsi::StringBuffer>(
      "console.log('SheetJS Library Version: ' + XLSX.version)"
    );
    auto js = rt->prepareJavaScript(src, std::string("<eval>"));
    rt->evaluatePreparedJavaScript(js);
  } catch (const facebook::jsi::JSIException &e) {
    std::cerr << "JavaScript terminated via uncaught exception: " << e.what() << '\n';
    return 1;
  }

  try {
    /* load payload as ArrayBuffer */
    size_t sz; char *data = read_file(argv[1], &sz);
    auto payload = std::make_shared<CMutableBuffer>(CMutableBuffer((uint8_t *)data, sz));
    auto ab = facebook::jsi::ArrayBuffer(*rt, payload);

    /* define stub function to read and convert first sheet to CSV */
    auto src = std::make_shared<facebook::jsi::StringBuffer>(
      "(function(buf) {"
        "var wb = XLSX.read(buf);"
        "return XLSX.utils.sheet_to_csv(wb.Sheets[wb.SheetNames[0]]);"
      "})"
    );
    auto js = rt->prepareJavaScript(src, std::string("<eval>"));
    auto func = rt->evaluatePreparedJavaScript(js);

    /* call stub function and capture result */
    auto csv = func.asObject(*rt).asFunction(*rt).call(*rt, ab);

    /* interpret as utf8 and print to stdout */
    std::string str = csv.getString(*rt).utf8(*rt);
    std::cout << str << std::endl;
  } catch (const facebook::jsi::JSIException &e) {
    std::cerr << "JavaScript terminated via uncaught exception: " << e.what() << std::endl;
    return 1;
  }

  return 0;
}